Discussion:
oscillator choice question
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c***@public.gmane.org
2010-05-01 19:28:04 UTC
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I'd like to build a GPS disciplined frequency standard.

I am slowly gathering up pieces.

I have a Trimble Resolution T GPS card that appears to work,
and an antenna for it.

I'm thinking now of the oscillator part.

I have two Racal 1992 counters with the stable oscillator option
(probably 04E since these are former military units). I also have an
old Schomandl ND-100M Frequenzdecade signal source with an (I assume)
ovenized oscillator w/unknown properties.

I'm wondering if I could use an oscillator from one of these
gizmos instead of shelling out real money on ebay? Speaking of
which, it seems like half the people in China are selling oscillators.
I assume some of them are good for this application and some not
so good? The usual suspects from HP and Agilent are there, and
they seem to command a pretty good (high) price. Which is why
I'm eyeing the Schomandl.

Chris
w0ep




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J. L. Trantham
2010-05-01 20:18:44 UTC
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Chris,

Careful. What you are contemplating can be very addicting.

I am not familiar with the units you mentioned but I have used the HP 10811.
They can be had for not much money on occasion but seem to be around $100
now days. One such example is 350335841291 on e..y.

I have also used an HP 105B which is a stand alone system that includes
power supply, battery back up, and puts out 5 MHz, 1 MHz and 100 KHz. Both
used Brooks Shera's controller card and seemed to work ok. It offers rather
easy integration with the GPS controller card as well as the ability to
remain on and fairly stable once disciplined.

I suspect this would be good as well, 180399463609, on e..y.

The Trimble Thunderbolt needs +5 VDC, +12 VDC and -12 VDC but is a self
contained GPSDO putting out 1 PPS and 10 MHz. Not much construction
required with this but needs a computer to monitor function.

How do you plan to discipline the oscillator?

Joe

-----Original Message-----
From: time-nuts-bounces-***@public.gmane.org [mailto:time-nuts-bounces-***@public.gmane.org] On
Behalf Of chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org
Sent: Saturday, May 01, 2010 2:28 PM
To: time-nuts-***@public.gmane.org
Subject: [time-nuts] oscillator choice question



I'd like to build a GPS disciplined frequency standard.

I am slowly gathering up pieces.

I have a Trimble Resolution T GPS card that appears to work, and an antenna
for it.

I'm thinking now of the oscillator part.

I have two Racal 1992 counters with the stable oscillator option
(probably 04E since these are former military units). I also have an
old Schomandl ND-100M Frequenzdecade signal source with an (I assume)
ovenized oscillator w/unknown properties.

I'm wondering if I could use an oscillator from one of these gizmos instead
of shelling out real money on ebay? Speaking of which, it seems like half
the people in China are selling oscillators. I assume some of them are good
for this application and some not so good? The usual suspects from HP and
Agilent are there, and they seem to command a pretty good (high) price.
Which is why I'm eyeing the Schomandl.

Chris
w0ep




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Robert Atkinson
2010-05-01 20:56:26 UTC
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Hi Chris,The Racal high stability units usually use the 9420 series OCXO's. These are good oscillators but do not have electronic tuning as standard. 'they are also normally 5MHz. What is the best oscillaor depends on your requirements. The two main parameters are phase noise and hold-over performance. Hold over is how much the oscillator will drift if the GPS loses signal.
Robert G8RPI.  

--- On Sat, 1/5/10, chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org <chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org> wrote:

From: chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org <chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org>
Subject: [time-nuts] oscillator choice question
To: time-nuts-***@public.gmane.org
Date: Saturday, 1 May, 2010, 20:28


I'd like to build a GPS disciplined frequency standard.

I am slowly gathering up pieces.

I have a Trimble Resolution T GPS card that appears to work,
and an antenna for it.

I'm thinking now of the oscillator part.

I have two Racal 1992 counters with the stable oscillator option (probably 04E since these are former military units).  I also have an old Schomandl  ND-100M Frequenzdecade signal source with an  (I assume) ovenized oscillator w/unknown properties.

I'm wondering if I could use an oscillator from one of these
gizmos instead of shelling out real money on ebay?  Speaking of
which, it seems like half the people in China are selling oscillators.
I assume some of them are good for this application and some not
so good?  The usual suspects from HP and Agilent are there, and
they seem to command a pretty good (high) price.  Which is why
I'm eyeing the Schomandl.

Chris
w0ep




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Bruce Griffiths
2010-05-01 21:44:44 UTC
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If there is no electronic tuning available one can use a DDS based
synthesiser to produce a corrected output frequency.
However close in spurs will be problematic unless one use a couple of
simple mix and divide stages or resorts to a Diophantine synthesiser
using phase noise truncation spur free output frequencies from the DDS
chip(s).

Alternatively if one implements the DDS in an FPGA its possible to
virtually eliminate such spurs using a modified algorithm.
However this requires an external DAC to produce the required output.

Bruce

Robert Atkinson wrote:
> Hi Chris,The Racal high stability units usually use the 9420 series OCXO's. These are good oscillators but do not have electronic tuning as standard. 'they are also normally 5MHz. What is the best oscillaor depends on your requirements. The two main parameters are phase noise and hold-over performance. Hold over is how much the oscillator will drift if the GPS loses signal.
> Robert G8RPI.
>
> --- On Sat, 1/5/10, chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org<chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org> wrote:
>
> From: chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org<chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org>
> Subject: [time-nuts] oscillator choice question
> To: time-nuts-***@public.gmane.org
> Date: Saturday, 1 May, 2010, 20:28
>
>
> I'd like to build a GPS disciplined frequency standard.
>
> I am slowly gathering up pieces.
>
> I have a Trimble Resolution T GPS card that appears to work,
> and an antenna for it.
>
> I'm thinking now of the oscillator part.
>
> I have two Racal 1992 counters with the stable oscillator option (probably 04E since these are former military units). I also have an old Schomandl ND-100M Frequenzdecade signal source with an (I assume) ovenized oscillator w/unknown properties.
>
> I'm wondering if I could use an oscillator from one of these
> gizmos instead of shelling out real money on ebay? Speaking of
> which, it seems like half the people in China are selling oscillators.
> I assume some of them are good for this application and some not
> so good? The usual suspects from HP and Agilent are there, and
> they seem to command a pretty good (high) price. Which is why
> I'm eyeing the Schomandl.
>
> Chris
> w0ep
>
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts-***@public.gmane.org
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>
>
>
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>



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Bob Camp
2010-05-02 00:23:22 UTC
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Hi

A lot depends on what sort of result you are looking for.

If a simple calibration of the standard in your counter to +/- 1 ppb is your goal, then a reasonable oscilloscope and some patience will get the job done with what you already have.

If continuos lock to GPS at a 10X or 100X tighter level is the goal, it's tough to beat a Thunderbolt at around $100.

Most modern gear is looking for a 10 MHz standard input. It's easier to start with 10 and divide for the item that wants 0.1, 1, or 5 MHz than to multiply up from something lower. I would limit my shopping list to OCXO's that already put out 10 MHz and have a voltage control input. There are usually a bunch of them being auctioned in the $50 range. If your accuracy requirement's aren't to tight, you can indeed use a TCXO. If you wait long enough, you probably can score a 10 MHz rubidium for $70 - they make fine GPSDO's ....

Regardless of the oscillator used, you will still need some sort of electronics in-between the Res-T and the oscillator. The complexity is up to you. A lot of what you are doing is the same weather you are running a TCXO or a Rb.

It all depends on you needs and your budget.

Bob


On May 1, 2010, at 3:28 PM, chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org wrote:

>
> I'd like to build a GPS disciplined frequency standard.
>
> I am slowly gathering up pieces.
>
> I have a Trimble Resolution T GPS card that appears to work,
> and an antenna for it.
>
> I'm thinking now of the oscillator part.
>
> I have two Racal 1992 counters with the stable oscillator option (probably 04E since these are former military units). I also have an old Schomandl ND-100M Frequenzdecade signal source with an (I assume) ovenized oscillator w/unknown properties.
>
> I'm wondering if I could use an oscillator from one of these
> gizmos instead of shelling out real money on ebay? Speaking of
> which, it seems like half the people in China are selling oscillators.
> I assume some of them are good for this application and some not
> so good? The usual suspects from HP and Agilent are there, and
> they seem to command a pretty good (high) price. Which is why
> I'm eyeing the Schomandl.
>
> Chris
> w0ep
>
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts-***@public.gmane.org
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>


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Hal Murray
2010-05-02 07:17:58 UTC
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bruce.griffiths-***@public.gmane.org said:
> If there is no electronic tuning available one can use a DDS based
> synthesiser to produce a corrected output frequency. However close in spurs
> will be problematic unless one use a couple of simple mix and divide stages
> or resorts to a Diophantine synthesiser using phase noise truncation spur
> free output frequencies from the DDS chip(s).

I think I understand the classic spurs from a DDS.

I wasn't familiar with Diophantine techniques. Google found this
http://www.hindawi.com/journals/ijno/2008/416958.html
which is readable at my level.

But I don't think I understand the big picture. The example numbers they
give involve mixing 500 Hz with 10 MHz. Assuming I want the sum, how do I
get rid of the difference? It's going to be a good strong signal, as strong
as the one I want. I think anything that leaks through the filter into the
next mixer is likely to make mirror sidebands that are right where we don't
want them.

Why is that going to be easier to get rid of than traditional spurs?



> Alternatively if one implements the DDS in an FPGA its possible to
> virtually eliminate such spurs using a modified algorithm. However this
> requires an external DAC to produce the required output.

Got a URL? What's magic about a FPGA? Why don't traditional DDS chips use
that modified algorithm?



--
These are my opinions, not necessarily my employer's. I hate spam.




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Bruce Griffiths
2010-05-02 08:51:51 UTC
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Hal Murray wrote:
> bruce.griffiths-***@public.gmane.org said:
>
>> If there is no electronic tuning available one can use a DDS based
>> synthesiser to produce a corrected output frequency. However close in spurs
>> will be problematic unless one use a couple of simple mix and divide stages
>> or resorts to a Diophantine synthesiser using phase noise truncation spur
>> free output frequencies from the DDS chip(s).
>>
> I think I understand the classic spurs from a DDS.
>
> I wasn't familiar with Diophantine techniques. Google found this
> http://www.hindawi.com/journals/ijno/2008/416958.html
> which is readable at my level.
>
> But I don't think I understand the big picture. The example numbers they
> give involve mixing 500 Hz with 10 MHz. Assuming I want the sum, how do I
> get rid of the difference? It's going to be a good strong signal, as strong
> as the one I want. I think anything that leaks through the filter into the
> next mixer is likely to make mirror sidebands that are right where we don't
> want them.
>
> Why is that going to be easier to get rid of than traditional spurs?
>
>
A DDS can generate some close in spurs that are very close to the
desired frequency and thus are difficult to filter even with a narrow
band PLL as the spur offset and amplitude varies with the DDS output
frequency in a very complex way.
A very narrow PLL requires a VCO with good short (for averaging times up
to the inverse PLL bandwidth) term stability.
However if the offset is 500Hz its relatively easy to filter out the
unwanted sum (or difference) frequency with a PLL using a VCO with good
short term stability for averaging times of a few tens of millisec. The
rejection can be improved by using an SSB mixer.

N.B. the author of the paper (and his web page) that you found has
vanished without trace.
It turns out that the Diophantine frequency synthesis technique was
patented (US Patent 5267182) some 17 years ago.
His literature search for previous papers/patents cant have been very
effective/extensive.
Fortunately I managed to download all of his papers before they vanished
along with the web page.
>
>
>> Alternatively if one implements the DDS in an FPGA its possible to
>> virtually eliminate such spurs using a modified algorithm. However this
>> requires an external DAC to produce the required output.
>>
> Got a URL? What's magic about a FPGA? Why don't traditional DDS chips use
> that modified algorithm?
>
>
>
>

http://www.sdrforum.org/pages/sdr06/sdr06_papers/1.3/1.3-01.pdf
(thanks to Bob Camp for finding this gem)

There's nothing magic about an FPGA, its merely a convenient way of
implementing the improved algorithm.
There's no way to implement it with a traditional DDS chip as the
digital section needs to be extensively modified.

DDS chips do not use it because it has only recently been devised.

Bruce


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jimlux
2010-05-02 16:27:00 UTC
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Hal Murray wrote:
> bruce.griffiths-***@public.gmane.org said:
>> If there is no electronic tuning available one can use a DDS based
>> synthesiser to produce a corrected output frequency. However close in spurs
>> will be problematic unless one use a couple of simple mix and divide stages
>> or resorts to a Diophantine synthesiser using phase noise truncation spur
>> free output frequencies from the DDS chip(s).
>
> I think I understand the classic spurs from a DDS.
>
> I wasn't familiar with Diophantine techniques. Google found this
> http://www.hindawi.com/journals/ijno/2008/416958.html
> which is readable at my level.
>
> But I don't think I understand the big picture. The example numbers they
> give involve mixing 500 Hz with 10 MHz. Assuming I want the sum, how do I
> get rid of the difference? It's going to be a good strong signal, as strong
> as the one I want. I think anything that leaks through the filter into the
> next mixer is likely to make mirror sidebands that are right where we don't
> want them.
>
> Why is that going to be easier to get rid of than traditional spurs?
>
>
>
>> Alternatively if one implements the DDS in an FPGA its possible to
>> virtually eliminate such spurs using a modified algorithm. However this
>> requires an external DAC to produce the required output.
>
> Got a URL? What's magic about a FPGA? Why don't traditional DDS chips use
> that modified algorithm?
>
>
>


Commercial DDSs are sold in large quantities for generalized
applications, so they tend not to use exotic techniques for spur
reduction over small ranges. You can also burn gates in exchange for
performance, a decision that would be tough to make for a manufacturer
concerned about power dissipation, etc.

It's easy, for instance, in a FPGA, to implement several different
length cosine lookup tables, so that all the frequencies you want to
generate exactly match the table length. You can also do things like
error filtering, various spur cancellation techniques, etc.



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Pete Rawson
2010-05-02 20:20:13 UTC
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Jim,

More technical stuff @ http://www.sotiriadis.info/

Pete Rawson

On May 2, 2010, at 10:27 AM, jimlux wrote:

> Hal Murray wrote:
>> bruce.griffiths-***@public.gmane.org said:
>>> If there is no electronic tuning available one can use a DDS based
>>> synthesiser to produce a corrected output frequency. However close in spurs
>>> will be problematic unless one use a couple of simple mix and divide stages
>>> or resorts to a Diophantine synthesiser using phase noise truncation spur
>>> free output frequencies from the DDS chip(s).
>> I think I understand the classic spurs from a DDS.
>> I wasn't familiar with Diophantine techniques. Google found this
>> http://www.hindawi.com/journals/ijno/2008/416958.html
>> which is readable at my level.
>> But I don't think I understand the big picture. The example numbers they give involve mixing 500 Hz with 10 MHz. Assuming I want the sum, how do I get rid of the difference? It's going to be a good strong signal, as strong as the one I want. I think anything that leaks through the filter into the next mixer is likely to make mirror sidebands that are right where we don't want them.
>> Why is that going to be easier to get rid of than traditional spurs?
>>> Alternatively if one implements the DDS in an FPGA its possible to
>>> virtually eliminate such spurs using a modified algorithm. However this
>>> requires an external DAC to produce the required output.
>> Got a URL? What's magic about a FPGA? Why don't traditional DDS chips use that modified algorithm?
>
>
> Commercial DDSs are sold in large quantities for generalized applications, so they tend not to use exotic techniques for spur reduction over small ranges. You can also burn gates in exchange for performance, a decision that would be tough to make for a manufacturer concerned about power dissipation, etc.
>
> It's easy, for instance, in a FPGA, to implement several different length cosine lookup tables, so that all the frequencies you want to generate exactly match the table length. You can also do things like error filtering, various spur cancellation techniques, etc.
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts-***@public.gmane.org
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Niels Lueddecke
2010-05-02 18:44:48 UTC
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Don't do it, it may drag you deep into nut territory...

All i wanted was a clock based on a cheap LPro rubidium.
Next thing i knew were strange things piling up on my desk.
Now theres a custom power supply, 7 AVRs on a couple of boards,
an FPGA running a 1GHz counter, a lump of metal and some rather
nice blinkenlights.

Does anybody else have an atomic clock with ir remote control,
a gregorian calendar (1582-29999), full leap year support,
all official holydays incl. easter date calculation, alarm mode
with snooze and 4 bit snooze period counter that is shifted out
in a kind of frequency modulation, a temp controlled fan for the
LPro, external c-field adjustment via d/a converter, pc interface
and software for logging, time setting and main avr memory dumps,
it even knows (quite acurately) how many ns its off the gps 1pps.

Did i mention the alarm can be set to only ring on days i have to work?
And it ain't even finished yet.

You see? Don't do it, don't even think about starting.
Go buy a trimble thunderbolt, it will save you LOTS of time!

http://www.dulli.org/pics/20100502%20-%20Clock.jpg


-------- Original-Nachricht --------
> Datum: Sat, 01 May 2010 14:28:04 -0500
> Von: "chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org" <chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org>
> An: time-nuts-***@public.gmane.org
> Betreff: [time-nuts] oscillator choice question

>
> I'd like to build a GPS disciplined frequency standard.
>
> I am slowly gathering up pieces.
>
> I have a Trimble Resolution T GPS card that appears to work,
> and an antenna for it.
>
> I'm thinking now of the oscillator part.
>
> I have two Racal 1992 counters with the stable oscillator option
> (probably 04E since these are former military units). I also have an
> old Schomandl ND-100M Frequenzdecade signal source with an (I assume)
> ovenized oscillator w/unknown properties.
>
> I'm wondering if I could use an oscillator from one of these
> gizmos instead of shelling out real money on ebay? Speaking of
> which, it seems like half the people in China are selling oscillators.
> I assume some of them are good for this application and some not
> so good? The usual suspects from HP and Agilent are there, and
> they seem to command a pretty good (high) price. Which is why
> I'm eyeing the Schomandl.
>
> Chris
> w0ep
>
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts-***@public.gmane.org
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.

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c***@public.gmane.org
2010-05-02 19:18:25 UTC
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That is a really cool picture.

Can I be like you when I grow up?


I've figured out which of these silvered modules
in this Schomandl sig gen is the oscillator (the one that
got warm). I have to figure out if it is voltage adjustable
in some way.

Does anyone use mechanical adjustment with a servo,
gear train and microcontroller?

I did hear all of those good advisers telling me to
buy the Thunderbolt. But I already have these pieces
so...

--
Chris
w0ep


Niels Lueddecke wrote:

> You see? Don't do it, don't even think about starting.
> Go buy a trimble thunderbolt, it will save you LOTS of time!
>
> http://www.dulli.org/pics/20100502%20-%20Clock.jpg
>

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Stanley Reynolds
2010-05-02 19:43:54 UTC
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Does anyone use mechanical adjustment with a servo,
gear train and microcontroller?

Might be useful as a tool to calibrate standards without electronic fine adjustment but would think it would ware out the capacitor if used to make continuous adjustments. Wonder if they make adjustment tools with a gear train ?

Stanley

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Bob Camp
2010-05-02 19:46:29 UTC
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Hi

A coupe of issues with mechanical servo tuning:

1) It wears out the tuning capacitor pretty fast. They are designed for a limited number of adjustments. They loosen up with a lot of tuning and this degrades their stability.

2) It would be much easier to tear apart the mechanical tune OCXO and put in a tuning diode than to rig a thermally isolated high resolution servo stepper

3) Mechanical tune arrangements normally have backlash. That's not an issue as long as the servo only goes one way. It becomes a real pain to correct for each time you reverse direction.

4) Making a mechanical setup with a minimum step below 1 ppt is going to be more than just a simple stepper. A gear chain based system will be pretty exciting to work up. Backlash in the gears will add to what ever you have in the tune it's self.

5) The tuning on the OCXO may not be monotonic. That's especially true if you do indeed run the trimmer at a higher resolution than a normal human could adjust it. Tuning reversals tend to drive servo loops a bit crazy.

None of that says that it can't be done. All it says is that it will be hard to do well.

What kind of accuracy are you trying to obtain?

Bob


On May 2, 2010, at 3:18 PM, chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org wrote:

> That is a really cool picture.
>
> Can I be like you when I grow up?
>
>
> I've figured out which of these silvered modules
> in this Schomandl sig gen is the oscillator (the one that
> got warm). I have to figure out if it is voltage adjustable
> in some way.
>
> Does anyone use mechanical adjustment with a servo,
> gear train and microcontroller?
>
> I did hear all of those good advisers telling me to
> buy the Thunderbolt. But I already have these pieces
> so...
>
> --
> Chris
> w0ep
>
>
> Niels Lueddecke wrote:
>
>> You see? Don't do it, don't even think about starting.
>> Go buy a trimble thunderbolt, it will save you LOTS of time!
>> http://www.dulli.org/pics/20100502%20-%20Clock.jpg
>
> _______________________________________________
> time-nuts mailing list -- time-nuts-***@public.gmane.org
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Bruce Griffiths
2010-05-02 19:54:27 UTC
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Bob Camp wrote:
> Hi
>
> A coupe of issues with mechanical servo tuning:
>
> 1) It wears out the tuning capacitor pretty fast. They are designed for a limited number of adjustments. They loosen up with a lot of tuning and this degrades their stability.
>
> 2) It would be much easier to tear apart the mechanical tune OCXO and put in a tuning diode than to rig a thermally isolated high resolution servo stepper
>
> 3) Mechanical tune arrangements normally have backlash. That's not an issue as long as the servo only goes one way. It becomes a real pain to correct for each time you reverse direction.
>
One solution to which is to add (in addition to the servo motor) a
torque motor to preload the gear train so that the same flank of each
gear tooth is in contact for both directions of rotation. Zero backlash
drive reduction systems are also available at some considerable cost.

> 4) Making a mechanical setup with a minimum step below 1 ppt is going to be more than just a simple stepper. A gear chain based system will be pretty exciting to work up. Backlash in the gears will add to what ever you have in the tune it's self.
>
> 5) The tuning on the OCXO may not be monotonic. That's especially true if you do indeed run the trimmer at a higher resolution than a normal human could adjust it. Tuning reversals tend to drive servo loops a bit crazy.
>
> None of that says that it can't be done. All it says is that it will be hard to do well.
>
> What kind of accuracy are you trying to obtain?
>
> Bob
>
>
Bruce

> On May 2, 2010, at 3:18 PM, chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org wrote:
>
>
>> That is a really cool picture.
>>
>> Can I be like you when I grow up?
>>
>>
>> I've figured out which of these silvered modules
>> in this Schomandl sig gen is the oscillator (the one that
>> got warm). I have to figure out if it is voltage adjustable
>> in some way.
>>
>> Does anyone use mechanical adjustment with a servo,
>> gear train and microcontroller?
>>
>> I did hear all of those good advisers telling me to
>> buy the Thunderbolt. But I already have these pieces
>> so...
>>
>> --
>> Chris
>> w0ep
>>
>>
>> Niels Lueddecke wrote:
>>
>>
>>> You see? Don't do it, don't even think about starting.
>>> Go buy a trimble thunderbolt, it will save you LOTS of time!
>>> http://www.dulli.org/pics/20100502%20-%20Clock.jpg
>>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts-***@public.gmane.org
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>>
>
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Bob Camp
2010-05-02 20:00:01 UTC
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Hi

An R-390A (or an not an A) has a lot of examples of how to do anti-backlash gear trains. Pretty tough to do on a one up fab from scratch in the basement basis though.

Lots easier to kludge in a low capacitance tuning diode .....

Bob


On May 2, 2010, at 3:54 PM, Bruce Griffiths wrote:

> Bob Camp wrote:
>> Hi
>>
>> A coupe of issues with mechanical servo tuning:
>>
>> 1) It wears out the tuning capacitor pretty fast. They are designed for a limited number of adjustments. They loosen up with a lot of tuning and this degrades their stability.
>>
>> 2) It would be much easier to tear apart the mechanical tune OCXO and put in a tuning diode than to rig a thermally isolated high resolution servo stepper
>>
>> 3) Mechanical tune arrangements normally have backlash. That's not an issue as long as the servo only goes one way. It becomes a real pain to correct for each time you reverse direction.
>>
> One solution to which is to add (in addition to the servo motor) a torque motor to preload the gear train so that the same flank of each gear tooth is in contact for both directions of rotation. Zero backlash drive reduction systems are also available at some considerable cost.
>
>> 4) Making a mechanical setup with a minimum step below 1 ppt is going to be more than just a simple stepper. A gear chain based system will be pretty exciting to work up. Backlash in the gears will add to what ever you have in the tune it's self.
>>
>> 5) The tuning on the OCXO may not be monotonic. That's especially true if you do indeed run the trimmer at a higher resolution than a normal human could adjust it. Tuning reversals tend to drive servo loops a bit crazy.
>>
>> None of that says that it can't be done. All it says is that it will be hard to do well.
>>
>> What kind of accuracy are you trying to obtain?
>>
>> Bob
>>
>>
> Bruce
>
>> On May 2, 2010, at 3:18 PM, chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org wrote:
>>
>>
>>> That is a really cool picture.
>>>
>>> Can I be like you when I grow up?
>>>
>>>
>>> I've figured out which of these silvered modules
>>> in this Schomandl sig gen is the oscillator (the one that
>>> got warm). I have to figure out if it is voltage adjustable
>>> in some way.
>>>
>>> Does anyone use mechanical adjustment with a servo,
>>> gear train and microcontroller?
>>>
>>> I did hear all of those good advisers telling me to
>>> buy the Thunderbolt. But I already have these pieces
>>> so...
>>>
>>> --
>>> Chris
>>> w0ep
>>>
>>>
>>> Niels Lueddecke wrote:
>>>
>>>
>>>> You see? Don't do it, don't even think about starting.
>>>> Go buy a trimble thunderbolt, it will save you LOTS of time!
>>>> http://www.dulli.org/pics/20100502%20-%20Clock.jpg
>>>>
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts-***@public.gmane.org
>>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>>
>>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts-***@public.gmane.org
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>>
>
>
>
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Neville Michie
2010-05-03 01:24:18 UTC
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Or you could rotate the whole OCXO on flexible leads through 180* and
let gravity tune your frequency.
The range might be small, but an occasional tweak on the frequency
control might be acceptible.
cheers, Neville Michie


On 03/05/2010, at 6:00 AM, Bob Camp wrote:

> Hi
>
> An R-390A (or an not an A) has a lot of examples of how to do anti-
> backlash gear trains. Pretty tough to do on a one up fab from
> scratch in the basement basis though.
>
> Lots easier to kludge in a low capacitance tuning diode .....
>
> Bob
>
>
> On May 2, 2010, at 3:54 PM, Bruce Griffiths wrote:
>
>> Bob Camp wrote:
>>> Hi
>>>
>>> A coupe of issues with mechanical servo tuning:
>>>
>>> 1) It wears out the tuning capacitor pretty fast. They are
>>> designed for a limited number of adjustments. They loosen up with
>>> a lot of tuning and this degrades their stability.
>>>
>>> 2) It would be much easier to tear apart the mechanical tune OCXO
>>> and put in a tuning diode than to rig a thermally isolated high
>>> resolution servo stepper
>>>
>>> 3) Mechanical tune arrangements normally have backlash. That's
>>> not an issue as long as the servo only goes one way. It becomes a
>>> real pain to correct for each time you reverse direction.
>>>
>> One solution to which is to add (in addition to the servo motor) a
>> torque motor to preload the gear train so that the same flank of
>> each gear tooth is in contact for both directions of rotation.
>> Zero backlash drive reduction systems are also available at some
>> considerable cost.
>>
>>> 4) Making a mechanical setup with a minimum step below 1 ppt is
>>> going to be more than just a simple stepper. A gear chain based
>>> system will be pretty exciting to work up. Backlash in the gears
>>> will add to what ever you have in the tune it's self.
>>>
>>> 5) The tuning on the OCXO may not be monotonic. That's especially
>>> true if you do indeed run the trimmer at a higher resolution than
>>> a normal human could adjust it. Tuning reversals tend to drive
>>> servo loops a bit crazy.
>>>
>>> None of that says that it can't be done. All it says is that it
>>> will be hard to do well.
>>>
>>> What kind of accuracy are you trying to obtain?
>>>
>>> Bob
>>>
>>>
>> Bruce
>>
>>> On May 2, 2010, at 3:18 PM, chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org wrote:
>>>
>>>
>>>> That is a really cool picture.
>>>>
>>>> Can I be like you when I grow up?
>>>>
>>>>
>>>> I've figured out which of these silvered modules
>>>> in this Schomandl sig gen is the oscillator (the one that
>>>> got warm). I have to figure out if it is voltage adjustable
>>>> in some way.
>>>>
>>>> Does anyone use mechanical adjustment with a servo,
>>>> gear train and microcontroller?
>>>>
>>>> I did hear all of those good advisers telling me to
>>>> buy the Thunderbolt. But I already have these pieces
>>>> so...
>>>>
>>>> --
>>>> Chris
>>>> w0ep
>>>>
>>>>
>>>> Niels Lueddecke wrote:
>>>>
>>>>
>>>>> You see? Don't do it, don't even think about starting.
>>>>> Go buy a trimble thunderbolt, it will save you LOTS of time!
>>>>> http://www.dulli.org/pics/20100502%20-%20Clock.jpg
>>>>>
>>>> _______________________________________________
>>>> time-nuts mailing list -- time-nuts-***@public.gmane.org
>>>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/
>>>> listinfo/time-nuts
>>>> and follow the instructions there.
>>>>
>>>>
>>>
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts-***@public.gmane.org
>>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/
>>> listinfo/time-nuts
>>> and follow the instructions there.
>>>
>>>
>>
>>
>>
>> _______________________________________________
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>> listinfo/time-nuts
>> and follow the instructions there.
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>
>
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Bob Camp
2010-05-03 01:30:30 UTC
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Hi

Certainly a lot less backlash than the mechanical trimmer. There would still be some minor issues due to the internal heat flow changing as you rotated the part. No obvious issues with wear out. Probably could use some kind of belt to drive a large wheel to get around the gear train. Six foot diameter wheel driven by a 1/4" shaft should do pretty well.

Bob


On May 2, 2010, at 9:24 PM, Neville Michie wrote:

> Or you could rotate the whole OCXO on flexible leads through 180* and let gravity tune your frequency.
> The range might be small, but an occasional tweak on the frequency control might be acceptible.
> cheers, Neville Michie
>
>
> On 03/05/2010, at 6:00 AM, Bob Camp wrote:
>
>> Hi
>>
>> An R-390A (or an not an A) has a lot of examples of how to do anti-backlash gear trains. Pretty tough to do on a one up fab from scratch in the basement basis though.
>>
>> Lots easier to kludge in a low capacitance tuning diode .....
>>
>> Bob
>>
>>
>> On May 2, 2010, at 3:54 PM, Bruce Griffiths wrote:
>>
>>> Bob Camp wrote:
>>>> Hi
>>>>
>>>> A coupe of issues with mechanical servo tuning:
>>>>
>>>> 1) It wears out the tuning capacitor pretty fast. They are designed for a limited number of adjustments. They loosen up with a lot of tuning and this degrades their stability.
>>>>
>>>> 2) It would be much easier to tear apart the mechanical tune OCXO and put in a tuning diode than to rig a thermally isolated high resolution servo stepper
>>>>
>>>> 3) Mechanical tune arrangements normally have backlash. That's not an issue as long as the servo only goes one way. It becomes a real pain to correct for each time you reverse direction.
>>>>
>>> One solution to which is to add (in addition to the servo motor) a torque motor to preload the gear train so that the same flank of each gear tooth is in contact for both directions of rotation. Zero backlash drive reduction systems are also available at some considerable cost.
>>>
>>>> 4) Making a mechanical setup with a minimum step below 1 ppt is going to be more than just a simple stepper. A gear chain based system will be pretty exciting to work up. Backlash in the gears will add to what ever you have in the tune it's self.
>>>>
>>>> 5) The tuning on the OCXO may not be monotonic. That's especially true if you do indeed run the trimmer at a higher resolution than a normal human could adjust it. Tuning reversals tend to drive servo loops a bit crazy.
>>>>
>>>> None of that says that it can't be done. All it says is that it will be hard to do well.
>>>>
>>>> What kind of accuracy are you trying to obtain?
>>>>
>>>> Bob
>>>>
>>>>
>>> Bruce
>>>
>>>> On May 2, 2010, at 3:18 PM, chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org wrote:
>>>>
>>>>
>>>>> That is a really cool picture.
>>>>>
>>>>> Can I be like you when I grow up?
>>>>>
>>>>>
>>>>> I've figured out which of these silvered modules
>>>>> in this Schomandl sig gen is the oscillator (the one that
>>>>> got warm). I have to figure out if it is voltage adjustable
>>>>> in some way.
>>>>>
>>>>> Does anyone use mechanical adjustment with a servo,
>>>>> gear train and microcontroller?
>>>>>
>>>>> I did hear all of those good advisers telling me to
>>>>> buy the Thunderbolt. But I already have these pieces
>>>>> so...
>>>>>
>>>>> --
>>>>> Chris
>>>>> w0ep
>>>>>
>>>>>
>>>>> Niels Lueddecke wrote:
>>>>>
>>>>>
>>>>>> You see? Don't do it, don't even think about starting.
>>>>>> Go buy a trimble thunderbolt, it will save you LOTS of time!
>>>>>> http://www.dulli.org/pics/20100502%20-%20Clock.jpg
>>>>>>
>>>>> _______________________________________________
>>>>> time-nuts mailing list -- time-nuts-***@public.gmane.org
>>>>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>>> and follow the instructions there.
>>>>>
>>>>>
>>>>
>>>> _______________________________________________
>>>> time-nuts mailing list -- time-nuts-***@public.gmane.org
>>>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>>> and follow the instructions there.
>>>>
>>>>
>>>
>>>
>>>
>>> _______________________________________________
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>>> and follow the instructions there.
>>>
>>
>>
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>
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c***@public.gmane.org
2010-05-02 20:13:31 UTC
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Bob asks a reasonable question:

> What kind of accuracy are you trying to obtain?
>
> Bob

I would like to end up with something that is usable
on a home electronics workbench. Something like a
Z3801. Something I can use if I ever try to do some
goofing around with microwave radio operation.

I'm not serious enough to want to spend hundreds
on a working unit. On the other hand, lashing up
something that works would count toward my
hobby/education so then it is ok to spend a little
bit of money.



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Bob Camp
2010-05-02 20:23:03 UTC
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Hi

Microwave radio suggests low spurs and often low phase noise. That's on top of the stability requirements.

In terms of stability a good Z3801 will run rings around a garden variety Thunderbolt. Both are significantly better on phase noise than a "garden variety" OCXO. You will need a *very* good OCXO to get to the performance level of either one. The 10811 is probably the easiest thing to both identify and find. You see them selling anywhere from $100 to $200 depending on just how patient you are.

Bob


On May 2, 2010, at 4:13 PM, chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org wrote:

>
> Bob asks a reasonable question:
>
>> What kind of accuracy are you trying to obtain?
>> Bob
>
> I would like to end up with something that is usable
> on a home electronics workbench. Something like a
> Z3801. Something I can use if I ever try to do some
> goofing around with microwave radio operation.
>
> I'm not serious enough to want to spend hundreds
> on a working unit. On the other hand, lashing up
> something that works would count toward my
> hobby/education so then it is ok to spend a little
> bit of money.
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts-***@public.gmane.org
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>


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c***@public.gmane.org
2010-05-16 21:30:18 UTC
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Thanks for all of your kind encouragement.

I gave up on using the NC100's oscillator for my GPSDO home-lab freq
standard. I was able to find a 10811 oscillator on ebay by
purchasing a non-working 5328A counter with the correct option.
It was very inexpensive and the 10811 appears to be alive.

Now I am reading Time-nuts history and I see that
there is no consensus on which of the popular/published GPSDO
configurations is the best return on effort and expense.
That is rather disappointing.

Any comments on that before I just flip a coin?



Bob Camp wrote:
> Hi
>
> Microwave radio suggests low spurs and often low phase noise. That's on top of the stability requirements.
>
> In terms of stability a good Z3801 will run rings around a garden variety Thunderbolt. Both are significantly better on phase noise than a "garden variety" OCXO. You will need a *very* good OCXO to get to the performance level of either one. The 10811 is probably the easiest thing to both identify and find. You see them selling anywhere from $100 to $200 depending on just how patient you are.
>
> Bob
>
>
> On May 2, 2010, at 4:13 PM, chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org wrote:
>
>> Bob asks a reasonable question:
>>
>>> What kind of accuracy are you trying to obtain?
>>> Bob
>> I would like to end up with something that is usable
>> on a home electronics workbench. Something like a
>> Z3801. Something I can use if I ever try to do some
>> goofing around with microwave radio operation.
>>
>> I'm not serious enough to want to spend hundreds
>> on a working unit. On the other hand, lashing up
>> something that works would count toward my
>> hobby/education so then it is ok to spend a little
>> bit of money.
>>
>>
>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts-***@public.gmane.org
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>
>
> _______________________________________________
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>
> ------------------------------------------------------------------------
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 9.0.814 / Virus Database: 271.1.1/2849 - Release Date: 05/02/10 01:27:00
>

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Bob Camp
2010-05-17 00:40:09 UTC
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Hi

The gotcha is that the Z38xx and TBolt do a pretty good job.

To do as well:

1) Build a counter with a < 1 ns resolution to compare the pps ticks. You want the resolution to be below the floor of a good timing receiver.
2) Set up a roughly 20 bit D/A to drive the EFC. More bits are always better. You can get away with 16 bits and tweaking fairly often. The objective is a LSB in the parts in 10^-13.
3) Put a good reference on the D/A. Voltage tuning on the EFC makes this tough to get around.
4) Set up a PIC or micro of your choice (Coldfire works quite well). You can get a *lot* of processor for $5 these days.
5) Probably lay out a pcb to put everything on.

Hook that all up to a good modern high sensitivity 12 channel timing grade GPS and start tuning your loop. You will need a good local reference to really get the tuning right.

This is in addition to the usual divide to 1 pps on the 10811, buffering of outputs, power supplies and regulation, and packaging.

Software wise, most people seem to wind up with some sort of software PID, possibly with coefficients that change as the unit stabilizes (Z38xx family) or not (TBolt ?).

Lots of work to get to "as good as". Of course you will be as good as the combined performance of the two, which is indeed better than either one by it's self.

Bob


On May 16, 2010, at 5:30 PM, chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org wrote:

> Thanks for all of your kind encouragement.
>
> I gave up on using the NC100's oscillator for my GPSDO home-lab freq standard. I was able to find a 10811 oscillator on ebay by
> purchasing a non-working 5328A counter with the correct option.
> It was very inexpensive and the 10811 appears to be alive.
>
> Now I am reading Time-nuts history and I see that
> there is no consensus on which of the popular/published GPSDO
> configurations is the best return on effort and expense.
> That is rather disappointing.
>
> Any comments on that before I just flip a coin?
>
>
>
> Bob Camp wrote:
>> Hi
>> Microwave radio suggests low spurs and often low phase noise. That's on top of the stability requirements.
>> In terms of stability a good Z3801 will run rings around a garden variety Thunderbolt. Both are significantly better on phase noise than a "garden variety" OCXO. You will need a *very* good OCXO to get to the performance level of either one. The 10811 is probably the easiest thing to both identify and find. You see them selling anywhere from $100 to $200 depending on just how patient you are.
>> Bob
>> On May 2, 2010, at 4:13 PM, chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org wrote:
>>> Bob asks a reasonable question:
>>>
>>>> What kind of accuracy are you trying to obtain?
>>>> Bob
>>> I would like to end up with something that is usable
>>> on a home electronics workbench. Something like a
>>> Z3801. Something I can use if I ever try to do some
>>> goofing around with microwave radio operation.
>>>
>>> I'm not serious enough to want to spend hundreds
>>> on a working unit. On the other hand, lashing up
>>> something that works would count toward my
>>> hobby/education so then it is ok to spend a little
>>> bit of money.
>>>
>>>
>>>
>>> _______________________________________________
>>> time-nuts mailing list -- time-nuts-***@public.gmane.org
>>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>>> and follow the instructions there.
>>>
>> _______________________________________________
>> time-nuts mailing list -- time-nuts-***@public.gmane.org
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>> ------------------------------------------------------------------------
>> No virus found in this incoming message.
>> Checked by AVG - www.avg.com Version: 9.0.814 / Virus Database: 271.1.1/2849 - Release Date: 05/02/10 01:27:00
>
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Stanley Reynolds
2010-05-17 01:19:19 UTC
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Parts for the Brooks Sheera W5OJM design are getting hard to find also need the extra divider mod for the 10 Mhz OCXO

The James Miller G3RUH design is popular for simple if you have the right GPS receiver with 100Khz out.

VE2ZAZ design has a few issues with ground loops ( a fix is out there) and using the same buffer for all outputs, may also need a buffer amp for the 10811, another mod would be a separate voltage regulator for the ECC voltage.

I think all three designs would fall short for most on the list, but for me it is hard to tell the difference.

Did you have another design in mind ?

Stanley


<snip>


Now I am reading Time-nuts history and I see that
there is no consensus on which of the popular/published GPSDO
configurations is the best return on effort and expense.
That is rather disappointing.

Any comments on that before I just flip a coin?

<snip>


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Bob Camp
2010-05-17 01:40:07 UTC
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Hi

Part of the issue is that some of the thinking on GPSDO's dates back to the era of selective availability on GPS. Designs from that era need to be upgraded to really get them to be all they can be with SA turned off.

Bob


On May 16, 2010, at 9:19 PM, Stanley Reynolds wrote:

> Parts for the Brooks Sheera W5OJM design are getting hard to find also need the extra divider mod for the 10 Mhz OCXO
>
> The James Miller G3RUH design is popular for simple if you have the right GPS receiver with 100Khz out.
>
> VE2ZAZ design has a few issues with ground loops ( a fix is out there) and using the same buffer for all outputs, may also need a buffer amp for the 10811, another mod would be a separate voltage regulator for the ECC voltage.
>
> I think all three designs would fall short for most on the list, but for me it is hard to tell the difference.
>
> Did you have another design in mind ?
>
> Stanley
>
>
> <snip>
>
>
> Now I am reading Time-nuts history and I see that
> there is no consensus on which of the popular/published GPSDO
> configurations is the best return on effort and expense.
> That is rather disappointing.
>
> Any comments on that before I just flip a coin?
>
> <snip>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts-***@public.gmane.org
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>


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e***@public.gmane.org
2010-05-17 20:58:26 UTC
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Hi,

there is a modified W5OJM GPSDO and all the PCB and so on......please see the flwng link

http://pagesperso-orange.fr/f5cau/base_temps_gps_f5cau/page_basegpsF5CAU.htm

Basically a well designed mods of the above idea.......and no special parts..... and it runs from 10MHz.....

Rgds Ernie.






-----Original Message-----
From: Bob Camp <lists-***@public.gmane.org>
To: Discussion of precise time and frequency measurement <time-nuts-***@public.gmane.org>
Sent: Mon, May 17, 2010 3:40 am
Subject: Re: [time-nuts] GPSDO - was - oscillator choice question


Hi
Part of the issue is that some of the thinking on GPSDO's dates back to the era
f selective availability on GPS. Designs from that era need to be upgraded to
eally get them to be all they can be with SA turned off.
Bob

n May 16, 2010, at 9:19 PM, Stanley Reynolds wrote:
> Parts for the Brooks Sheera W5OJM design are getting hard to find also need
he extra divider mod for the 10 Mhz OCXO

The James Miller G3RUH design is popular for simple if you have the right GPS
eceiver with 100Khz out.

VE2ZAZ design has a few issues with ground loops ( a fix is out there) and
sing the same buffer for all outputs, may also need a buffer amp for the 10811,
nother mod would be a separate voltage regulator for the ECC voltage.

I think all three designs would fall short for most on the list, but for me it
s hard to tell the difference.

Did you have another design in mind ?

Stanley


<snip>


Now I am reading Time-nuts history and I see that
there is no consensus on which of the popular/published GPSDO
configurations is the best return on effort and expense.
That is rather disappointing.

Any comments on that before I just flip a coin?

<snip>


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o unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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c***@public.gmane.org
2010-05-03 20:02:04 UTC
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Raw Message
just for show-and-tell:

I've been disassembling the Schmomandl ND100M oscillator
block to see if I could use it. I figured, it's the bird
in hand, and once was a high quality piece of equipment
so maybe...

The physical construction is great. Lots of fine pitch
slot head machine screws. Lots of silver plating.


The oscillator unit is long and narrow. It goes
in the 19" rack mount unit in the "depth" direction,
front to back in the upper left hand corner of what
turns out to be a more or less solid block of plated
boxes that make up the whole frequency generator.
Decade controls on the front are switches only. Each
is wired to a decade unit/card and the decade units are
fed signal all in series. Computerish connectors
at the back reproduce the decade switches in some
manner, so the thing can be remotely controlled
for frequency output.


I have four rough pictures.

www.yipyap.com/radio_stuff/ND100M/One.pdf is right (rear)
end of the component side.

www.yipyap.com/radio_stuff/ND100M/Four.pdf is the left (front)
end of the component side.

www.yipyap.com/radio_stuff/ND100M/Two.pdf is a blurry closeup
of the center from the trace side.

www.yipyap.com/radio_stuff/ND100M/Three.pdf shows the
power connector (+13.6, -11), two series resistors on those
power lines, and 8 output lines. Some of the outputs are
10 Mhz. At least one is 1 Mhz.

The center crystal cannister is electrically isolated.
It is on acrylic stand offs. Even the trimmer control
uses a smaller acrylic rod within a larger acrylic
tube/standoff. And the L-shaped piece directly to
the right of the cannister, from which it is supported, is
itself on long standoffs from the right end piece.
There are 3 sets of 4 fine wires coming
out of the crystal cannister, two go to the little board
on the right, one goes to the larger board on the left
(the output board). The crystal cannister was surrounded
with white extruded foam of the same kind as a cheap
picnic cooler.

I removed some of the silver "fingers" around the
crystal cannister area to remove the insulation.

I don't know what the board on the right end does.. maybe
temperature control? The board on the left end seems to be
output buffer/filter.

I don't think I am going to tear this down any further,
and I also don't think I see any easy way for me to adjust
the frequency electronically without ripping into the
crystal cannister and I don't trust my ability to
put it back together in working order.

If you all have suggestions otherwise, fire away.

Chris





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Rex
2010-05-03 20:21:19 UTC
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Raw Message
Chris, your links don't work.


chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org wrote:
>
> just for show-and-tell:
>
> ...

> I have four rough pictures.
>
> www.yipyap.com/radio_stuff/ND100M/One.pdf is right (rear)
> end of the component side.
>
> www.yipyap.com/radio_stuff/ND100M/Four.pdf is the left (front)
> end of the component side.
>
> www.yipyap.com/radio_stuff/ND100M/Two.pdf is a blurry closeup
> of the center from the trace side.
>
> www.yipyap.com/radio_stuff/ND100M/Three.pdf shows the
> power connector (+13.6, -11), two series resistors on those
> power lines, and 8 output lines. Some of the outputs are
> 10 Mhz. At least one is 1 Mhz.
>


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larrys-t1x0RZC3KMfqlBn2x/ (Larry Snyder)
2010-05-03 20:25:16 UTC
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"chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org" <chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org> wrote:
>
> just for show-and-tell:

404 :-(
-ls-


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c***@public.gmane.org
2010-05-03 20:27:26 UTC
Reply
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Raw Message
sorry, revised with correct URL's.

chris-h5BGtkwdqq/QT0dZR+***@public.gmane.org wrote:
>
> just for show-and-tell:
>
> I've been disassembling the Schmomandl ND100M oscillator
> block to see if I could use it. I figured, it's the bird
> in hand, and once was a high quality piece of equipment
> so maybe...
>
> The physical construction is great. Lots of fine pitch
> slot head machine screws. Lots of silver plating.
>
>
> The oscillator unit is long and narrow. It goes
> in the 19" rack mount unit in the "depth" direction,
> front to back in the upper left hand corner of what
> turns out to be a more or less solid block of plated
> boxes that make up the whole frequency generator.
> Decade controls on the front are switches only. Each
> is wired to a decade unit/card and the decade units are
> fed signal all in series. Computerish connectors
> at the back reproduce the decade switches in some
> manner, so the thing can be remotely controlled
> for frequency output.
>
>
> I have four rough pictures.
>
www.yipyap.com/radio_stuff/ND100M/One.jpg is right (rear)
> end of the component side.
>
www.yipyap.com/radio_stuff/ND100M/Four.jpg is the left (front)
> end of the component side.
>
www.yipyap.com/radio_stuff/ND100M/Two.jpg is a blurry closeup
> of the center from the trace side.
>
www.yipyap.com/radio_stuff/ND100M/Three.jpg shows the
> power connector (+13.6, -11), two series resistors on those
> power lines, and 8 output lines. Some of the outputs are
> 10 Mhz. At least one is 1 Mhz.
>
> The center crystal cannister is electrically isolated.
> It is on acrylic stand offs. Even the trimmer control
> uses a smaller acrylic rod within a larger acrylic
> tube/standoff. And the L-shaped piece directly to
> the right of the cannister, from which it is supported, is
> itself on long standoffs from the right end piece.
> There are 3 sets of 4 fine wires coming
> out of the crystal cannister, two go to the little board
> on the right, one goes to the larger board on the left
> (the output board). The crystal cannister was surrounded
> with white extruded foam of the same kind as a cheap
> picnic cooler.
>
> I removed some of the silver "fingers" around the
> crystal cannister area to remove the insulation.
>
> I don't know what the board on the right end does.. maybe
> temperature control? The board on the left end seems to be
> output buffer/filter.
>
> I don't think I am going to tear this down any further,
> and I also don't think I see any easy way for me to adjust
> the frequency electronically without ripping into the
> crystal cannister and I don't trust my ability to
> put it back together in working order.
>
> If you all have suggestions otherwise, fire away.
>
> Chris
>
>
>
>
>
> ------------------------------------------------------------------------
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 9.0.814 / Virus Database: 271.1.1/2851 - Release Date: 05/03/10 01:27:00
>

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Luis Cupido
2010-05-04 09:52:10 UTC
Reply
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Raw Message
Hi,

I'm looking for a relatively simple PLL chip
like LMX1501 or similar.

I mean, looking for a new design, that is something
that is easy to source (known to be in production etc)
recent/modern enough to provide a low phase noise.

Is for VHF/UHF below 500MHz application and will
be for MHz steps (no small steps required).
Albeit reasonably low phase noise will be wanted.


What seems to be available from An.Dev. and Nat.Sem.
are way too unnecessarily complex and I would like
it to not have a zilion registers to load via spi.
(might use just a small corner of a CPLD to load it).

Are the simple ones gone obsolete, or simple no longer in the
web pages ???

ok... I think you got the idea...
I'm looking for the basic think...

Any suggestions of what might be usable/available.


Thanks.

Luis Cupido
ct1dmk.


p.s. I know it doesn't matter to have a modern complex one
as some microcontroller will be programming it etc etc...
That I know already ;-) ... no need to tell me :-)
but... if a simple ones exist why should I go complex !

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Bob Camp
2010-05-04 11:55:14 UTC
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Hi

The complex parts are now the low end. The high end parts have stuff
like sigma delta on them. The 4001 from AD is about as simple as they
get these days.


Bob



On May 4, 2010, at 5:52 AM, Luis Cupido <cupido-r+***@public.gmane.org> wrot
> Hi,
>
> I'm looking for a relatively simple PLL chip
> like LMX1501 or similar.
>
> I mean, looking for a new design, that is something
> that is easy to source (known to be in production etc)
> recent/modern enough to provide a low phase noise.
>
> Is for VHF/UHF below 500MHz application and will
> be for MHz steps (no small steps required).
> Albeit reasonably low phase noise will be wanted.
>
>
> What seems to be available from An.Dev. and Nat.Sem.
> are way too unnecessarily complex and I would like
> it to not have a zilion registers to load via spi.
> (might use just a small corner of a CPLD to load it).
>
> Are the simple ones gone obsolete, or simple no longer in the
> web pages ???
>
> ok... I think you got the idea...
> I'm looking for the basic think...
>
> Any suggestions of what might be usable/available.
>
>
> Thanks.
>
> Luis Cupido
> ct1dmk.
>
>
> p.s. I know it doesn't matter to have a modern complex one
> as some microcontroller will be programming it etc etc...
> That I know already ;-) ... no need to tell me :-)
> but... if a simple ones exist why should I go complex !
>
> _______________________________________________
> time-nuts mailing list -- time-nuts-***@public.gmane.org
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>

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jimlux
2010-05-04 13:01:57 UTC
Reply
Permalink
Raw Message
Luis Cupido wrote:
> Hi,
>
> I'm looking for a relatively simple PLL chip
> like LMX1501 or similar.
>
> I mean, looking for a new design, that is something
> that is easy to source (known to be in production etc)
> recent/modern enough to provide a low phase noise.
>
> Is for VHF/UHF below 500MHz application and will
> be for MHz steps (no small steps required).
> Albeit reasonably low phase noise will be wanted.
>
>
> What seems to be available from An.Dev. and Nat.Sem.
> are way too unnecessarily complex and I would like
> it to not have a zilion registers to load via spi.
> (might use just a small corner of a CPLD to load it).
>
> Are the simple ones gone obsolete, or simple no longer in the
> web pages ???
>
> ok... I think you got the idea...
> I'm looking for the basic think...
>
> Any suggestions of what might be usable/available.
>

How about the Peregrine 9701? Pretty low noise, simple (20 bit serial
word to load).. Max reference divider is 63 or 64.

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jimlux
2010-05-04 13:08:56 UTC
Reply
Permalink
Raw Message
Luis Cupido wrote:
> Hi,
>
> I'm looking for a relatively simple PLL chip
> like LMX1501 or similar.
>
> I mean, looking for a new design, that is something
> that is easy to source (known to be in production etc)
> recent/modern enough to provide a low phase noise.
>
> Is for VHF/UHF below 500MHz application and will
> be for MHz steps (no small steps required).
> Albeit reasonably low phase noise will be wanted.
>
>
> What seems to be available from An.Dev. and Nat.Sem.
> are way too unnecessarily complex and I would like
> it to not have a zilion registers to load via spi.
> (might use just a small corner of a CPLD to load it).
>
> Are the simple ones gone obsolete, or simple no longer in the
> web pages ???
>
> ok... I think you got the idea...
> I'm looking for the basic think...
>
> Any suggestions of what might be usable/available.
>
>
> Thanks.
>
> Luis Cupido
> ct1dmk.
>


Or Fujitsu (e.g. MB15E03SL)

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Nick Foster
2010-05-04 17:58:19 UTC
Reply
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Raw Message
If you're thinking about using a CPLD to load registers in a PLL chip, why not just implement the PLL on the CPLD? After all, if you're looking for simpler-is-better, there's not much on a dedicated PLL chip that you can't easily replicate in CPLD with some care and attention paid to layout.

----------------------------------------
> Date: Tue, 4 May 2010 06:08:56 -0700
> From: jimlux-***@public.gmane.org
> To: time-nuts-***@public.gmane.org
> Subject: Re: [time-nuts] Simple PLL chips, gone ?
>
> Luis Cupido wrote:
>> Hi,
>>
>> I'm looking for a relatively simple PLL chip
>> like LMX1501 or similar.
>>
>> I mean, looking for a new design, that is something
>> that is easy to source (known to be in production etc)
>> recent/modern enough to provide a low phase noise.
>>
>> Is for VHF/UHF below 500MHz application and will
>> be for MHz steps (no small steps required).
>> Albeit reasonably low phase noise will be wanted.
>>
>>
>> What seems to be available from An.Dev. and Nat.Sem.
>> are way too unnecessarily complex and I would like
>> it to not have a zilion registers to load via spi.
>> (might use just a small corner of a CPLD to load it).
>>
>> Are the simple ones gone obsolete, or simple no longer in the
>> web pages ???
>>
>> ok... I think you got the idea...
>> I'm looking for the basic think...
>>
>> Any suggestions of what might be usable/available.
>>
>>
>> Thanks.
>>
>> Luis Cupido
>> ct1dmk.
>>
>
>
> Or Fujitsu (e.g. MB15E03SL)
>
> _______________________________________________
> time-nuts mailing list -- time-nuts-***@public.gmane.org
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.

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jimlux
2010-05-04 22:20:38 UTC
Reply
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Raw Message
Nick Foster wrote:
> If you're thinking about using a CPLD to load registers in a PLL chip, why not just implement the PLL on the CPLD? After all, if you're looking for simpler-is-better, there's not much on a dedicated PLL chip that you can't easily replicate in CPLD with some care and attention paid to layout.
>


Most CPLDs don't have low noise phase frequency detectors, the charge
pump, or the analog parts to make the loop filter.

Jim

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Christopher Hoover
2010-05-05 01:35:34 UTC
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On 5/4/2010 5:00 AM, Luis Cupido wrote:
> that is something that is easy to source (known to be in production etc)
>

"easy to source" and "known to be in production" are very much a mixed
bag lately. after the economic slow down, many plants in china and
other locales let large numbers of workers go. if you can find a
stocking supplier with parts in hand, you are good to go. but beyond
that you are likely to find trouble. i have been told that getting
factories to ramp up production has been difficult. parts in demand by
big buyers naturally get preference, and the envelope of parts used by
consumer goods is but a fraction of all parts offered.

-ch


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Richard W. Solomon
2010-05-17 21:52:47 UTC
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Raw Message
Will the boards be available for purchase ? I would like to
build two of them.

73, Dick, W1KSZ


-----Original Message-----
>From: ernieperes-***@public.gmane.org
>Sent: May 17, 2010 4:58 PM
>To: time-nuts-***@public.gmane.org
>Subject: Re: [time-nuts] GPSDO - was - oscillator choice question
>
>
>
>Hi,
>
>there is a modified W5OJM GPSDO and all the PCB and so on......please see the flwng link
>
>http://pagesperso-orange.fr/f5cau/base_temps_gps_f5cau/page_basegpsF5CAU.htm
>
>Basically a well designed mods of the above idea.......and no special parts..... and it runs from 10MHz.....
>
>Rgds Ernie.
>
>
>
>
>
>
>-----Original Message-----
>From: Bob Camp <lists-***@public.gmane.org>
>To: Discussion of precise time and frequency measurement <time-nuts-***@public.gmane.org>
>Sent: Mon, May 17, 2010 3:40 am
>Subject: Re: [time-nuts] GPSDO - was - oscillator choice question
>
>
>Hi
>Part of the issue is that some of the thinking on GPSDO's dates back to the era
>f selective availability on GPS. Designs from that era need to be upgraded to
>eally get them to be all they can be with SA turned off.
>Bob
>
>n May 16, 2010, at 9:19 PM, Stanley Reynolds wrote:
>> Parts for the Brooks Sheera W5OJM design are getting hard to find also need
>he extra divider mod for the 10 Mhz OCXO
>
> The James Miller G3RUH design is popular for simple if you have the right GPS
>eceiver with 100Khz out.
>
> VE2ZAZ design has a few issues with ground loops ( a fix is out there) and
>sing the same buffer for all outputs, may also need a buffer amp for the 10811,
>nother mod would be a separate voltage regulator for the ECC voltage.
>
> I think all three designs would fall short for most on the list, but for me it
>s hard to tell the difference.
>
> Did you have another design in mind ?
>
> Stanley
>
>
> <snip>
>
>
> Now I am reading Time-nuts history and I see that
> there is no consensus on which of the popular/published GPSDO
> configurations is the best return on effort and expense.
> That is rather disappointing.
>
> Any comments on that before I just flip a coin?
>
> <snip>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts-***@public.gmane.org
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>
>______________________________________________
>ime-nuts mailing list -- time-nuts-***@public.gmane.org
>o unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>nd follow the instructions there.
>
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>To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>and follow the instructions there.


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e***@public.gmane.org
2010-05-18 05:54:17 UTC
Reply
Permalink
Raw Message
Hi Dick,

Please contact directly with F5CAU about the PCB and PIC code.....
also there is a VE2ZAZ based GPSDO......please see this link.....

http://rxcontrol.free.fr/PicGPS/index.html


Rgds Ernie.








-----Original Message-----
From: Richard W. Solomon <w1ksz-***@public.gmane.org>
To: Discussion of precise time and frequency measurement <time-nuts-***@public.gmane.org>
Sent: Mon, May 17, 2010 11:52 pm
Subject: Re: [time-nuts] GPSDO - was - oscillator choice question


Will the boards be available for purchase ? I would like to
uild two of them.
73, Dick, W1KSZ

----Original Message-----
From: ernieperes-***@public.gmane.org
Sent: May 17, 2010 4:58 PM
To: time-nuts-***@public.gmane.org
Subject: Re: [time-nuts] GPSDO - was - oscillator choice question



Hi,

there is a modified W5OJM GPSDO and all the PCB and so on......please see the
lwng link

http://pagesperso-orange.fr/f5cau/base_temps_gps_f5cau/page_basegpsF5CAU.htm

Basically a well designed mods of the above idea.......and no special
arts..... and it runs from 10MHz.....

Rgds Ernie.






-----Original Message-----
From: Bob Camp <lists-***@public.gmane.org>
To: Discussion of precise time and frequency measurement <time-nuts-***@public.gmane.org>
Sent: Mon, May 17, 2010 3:40 am
Subject: Re: [time-nuts] GPSDO - was - oscillator choice question


Hi
Part of the issue is that some of the thinking on GPSDO's dates back to the era
>f selective availability on GPS. Designs from that era need to be upgraded to
eally get them to be all they can be with SA turned off.
Bob

n May 16, 2010, at 9:19 PM, Stanley Reynolds wrote:
> Parts for the Brooks Sheera W5OJM design are getting hard to find also need
he extra divider mod for the 10 Mhz OCXO

The James Miller G3RUH design is popular for simple if you have the right GPS
eceiver with 100Khz out.

VE2ZAZ design has a few issues with ground loops ( a fix is out there) and
sing the same buffer for all outputs, may also need a buffer amp for the 10811,
>nother mod would be a separate voltage regulator for the ECC voltage.

I think all three designs would fall short for most on the list, but for me it
>s hard to tell the difference.

Did you have another design in mind ?

Stanley


<snip>


Now I am reading Time-nuts history and I see that
there is no consensus on which of the popular/published GPSDO
configurations is the best return on effort and expense.
That is rather disappointing.

Any comments on that before I just flip a coin?

<snip>


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Hal Murray
2010-06-29 18:39:43 UTC
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bruce.griffiths-***@public.gmane.org said:
> Its possible to build a 24 bit resolution D/A using a synchronously
> filtered PWM circuit. A pair of PWM outputs and a few relatively low
> precision resistors and capacitors together with a low noise low drift
> reference are required. The technique takes advantage of the fact that the
> required EFC voltage changes slowly and isnt updated at a highg rate. The
> synchronous filter technique eliminates the very long time constant RC
> filters required with an asynchronously filtered PWM waveform.

24 bits is 16,777,216. At a reasonable clock rate, that's one second.

Another approach is to distribute the individual bits rather than clump them
together. If you want 1/2, send 10101010 rather than 11110000. You would
have to do something like build a bit pattern in memory and use a serial port
to send it out.

That shifts the frequency of the junk so that it's easier to filter out
and/or reduces the amplitude. If you send 10101010, you have lots of energy
but it's at 8 MHz. If you send 1000000, you have energy at 1 Hz, but it's
only 1/16000000 as big. Or something like that. [Since this is a linear
system, you will get that spur with any odd number of 1s.]

I can't determine if that's good enough. I think the math is similar to the
spurs you get from a DDS.




--
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Bruce Griffiths
2010-06-29 20:28:38 UTC
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Hal Murray wrote:
> bruce.griffiths-***@public.gmane.org said:
>
>> Its possible to build a 24 bit resolution D/A using a synchronously
>> filtered PWM circuit. A pair of PWM outputs and a few relatively low
>> precision resistors and capacitors together with a low noise low drift
>> reference are required. The technique takes advantage of the fact that the
>> required EFC voltage changes slowly and isnt updated at a highg rate. The
>> synchronous filter technique eliminates the very long time constant RC
>> filters required with an asynchronously filtered PWM waveform.
>>
> 24 bits is 16,777,216. At a reasonable clock rate, that's one second.
>
Not if one uses a pair of 16bit PWM circuits to produce a DAC with 24
bit resolution.
a few 0.1% resistors then suffice to achieve 24 bit linearity.
> Another approach is to distribute the individual bits rather than clump them
> together. If you want 1/2, send 10101010 rather than 11110000. You would
> have to do something like build a bit pattern in memory and use a serial port
> to send it out.
>

With a synchronous filter the settling time (for small output changes)
is equal to the PWM period.
The synchronous filter uses a variation of a dual slope error
integrator, the output of which when sampled is equal to the desired output.
The effect of dielectric absorption in the error integrator can be
reduced by implementing a mutislope integrator rather than a dual slope
version.
Its then possible to use a pair of 8 bit PWM signals to achieve 24 bit
resolution.

> That shifts the frequency of the junk so that it's easier to filter out
> and/or reduces the amplitude. If you send 10101010, you have lots of energy
> but it's at 8 MHz. If you send 1000000, you have energy at 1 Hz, but it's
> only 1/16000000 as big. Or something like that. [Since this is a linear
> system, you will get that spur with any odd number of 1s.]
>
> I can't determine if that's good enough. I think the math is similar to the
> spurs you get from a DDS.
>
>
>
Simulated that, and Ulrich did some testing, the spurs can be problematic.

The synchronous PWM circuit is much easier to filter as the synchronous
output noise amplitude (with a constant input) due to sampling charge
injection need not be more than a few microvolts. That is there is a
small spur with an amplitude of a few microvolts at the PWM repetition rate.

>
>


Bruce
Hal Murray
2010-06-29 19:55:10 UTC
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> Another approach is to distribute the individual bits rather than clump them
> together. If you want 1/2, send 10101010 rather than 11110000. You would
> have to do something like build a bit pattern in memory and use a serial
> port to send it out.

> I can't determine if that's good enough. I think the math is similar to the
> spurs you get from a DDS.

I'm getting slow in my old age...

You can also generate the bit pattern on the fly. It's the same logic as a
DDS: just an adder. If you want the D/A to output X (as a fraction) just add
X to your register each clock cycle. (I think of the register as having the
decimal point on the left.)

With a DDS, you would feed the top bits to a D/A. For the distributed PWM
(Pulse Density Modulation?) use the carry out of the top bit.


--
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Hal Murray
2011-04-10 00:59:27 UTC
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bruce.griffiths-***@public.gmane.org said:
> The 16MHz is necessary for the loop to function: The mixer mixes down the
> 26MHz to a pair of conjugate frequencies, 10MHz and 16MHz. Thermal and
> device noise is sufficient to start the process.

> 10MHz = 26MHz - 16MHz
> 16MHz = 26MHz - 10MHz

What makes it stable at 10 and 16 MHz rather than 10.000001 and 15.999999?

I'm assuming we are starting with a good 26 MHz crystal and that it would be hard to get filters that good.


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Greg Broburg
2011-04-10 02:38:07 UTC
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10.000005 = 26 - 15.999995

15.999995 = 26 - 10.000005

This pair of equations is insufficient to define
that the ratio between these two frequencies
is exactly 1.6 : 1 or 1 : 1.6

There must be an additional concept here.

Greg


On 4/9/2011 6:59 PM, Hal Murray wrote:
> bruce.griffiths-***@public.gmane.org said:
>> The 16MHz is necessary for the loop to function: The mixer mixes down the
>> 26MHz to a pair of conjugate frequencies, 10MHz and 16MHz. Thermal and
>> device noise is sufficient to start the process.
>> 10MHz = 26MHz - 16MHz
>> 16MHz = 26MHz - 10MHz
> What makes it stable at 10 and 16 MHz rather than 10.000001 and 15.999999?
>
> I'm assuming we are starting with a good 26 MHz crystal and that it would be hard to get filters that good.
>
>
Bruce Griffiths
2011-04-10 01:46:10 UTC
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There are also loop gain and phase shift requirements to be met for
stable operation (ie with no asynchronous modes).

Bruce

Greg Broburg wrote:
> 10.000005 = 26 - 15.999995
>
> 15.999995 = 26 - 10.000005
>
> This pair of equations is insufficient to define
> that the ratio between these two frequencies
> is exactly 1.6 : 1 or 1 : 1.6
>
> There must be an additional concept here.
>
> Greg
>
>
> On 4/9/2011 6:59 PM, Hal Murray wrote:
>> bruce.griffiths-***@public.gmane.org said:
>>> The 16MHz is necessary for the loop to function: The mixer mixes
>>> down the
>>> 26MHz to a pair of conjugate frequencies, 10MHz and 16MHz. Thermal and
>>> device noise is sufficient to start the process.
>>> 10MHz = 26MHz - 16MHz
>>> 16MHz = 26MHz - 10MHz
>> What makes it stable at 10 and 16 MHz rather than 10.000001 and
>> 15.999999?
>>
>> I'm assuming we are starting with a good 26 MHz crystal and that it
>> would be hard to get filters that good.
>>
>>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts-***@public.gmane.org
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
Bruce Griffiths
2011-04-10 01:43:04 UTC
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Hal Murray wrote:
> bruce.griffiths-***@public.gmane.org said:
>
>> The 16MHz is necessary for the loop to function: The mixer mixes down the
>> 26MHz to a pair of conjugate frequencies, 10MHz and 16MHz. Thermal and
>> device noise is sufficient to start the process.
>>
>
>> 10MHz = 26MHz - 16MHz
>> 16MHz = 26MHz - 10MHz
>>
> What makes it stable at 10 and 16 MHz rather than 10.000001 and 15.999999?
>
> I'm assuming we are starting with a good 26 MHz crystal and that it would be hard to get filters that good.
>
>
>
Asynchronous modes such as 10.000001MHz plus 15.999999 MHz can be
problematic if the loop delay is too high.
http://www.femto-st.fr/~rubiola/pdf-articles/journal/1992im%28rubiola%29regenerative-divider-noise.pdf
<http://www.femto-st.fr/%7Erubiola/pdf-articles/journal/1992im%28rubiola%29regenerative-divider-noise.pdf>

http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F26%2F23863%2F01093262.pdf%3Farnumber%3D1093262&authDecision=-203
<http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F26%2F23863%2F01093262.pdf%3Farnumber%3D1093262&authDecision=-203>

http://tf.nist.gov/general/pdf/1800.pdf

Bruce
Bruce Griffiths
2011-04-10 20:08:32 UTC
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Bruce Griffiths wrote:
> Hal Murray wrote:
>> bruce.griffiths-***@public.gmane.org said:
>>> The 16MHz is necessary for the loop to function: The mixer mixes
>>> down the
>>> 26MHz to a pair of conjugate frequencies, 10MHz and 16MHz. Thermal and
>>> device noise is sufficient to start the process.
>>> 10MHz = 26MHz - 16MHz
>>> 16MHz = 26MHz - 10MHz
>> What makes it stable at 10 and 16 MHz rather than 10.000001 and
>> 15.999999?
>>
>> I'm assuming we are starting with a good 26 MHz crystal and that it
>> would be hard to get filters that good.
>>
>>
> Asynchronous modes such as 10.000001MHz plus 15.999999 MHz can be
> problematic if the loop delay is too high.
> http://www.femto-st.fr/~rubiola/pdf-articles/journal/1992im%28rubiola%29regenerative-divider-noise.pdf
> <http://www.femto-st.fr/%7Erubiola/pdf-articles/journal/1992im%28rubiola%29regenerative-divider-noise.pdf>
>
>
> http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F26%2F23863%2F01093262.pdf%3Farnumber%3D1093262&authDecision=-203
> <http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F26%2F23863%2F01093262.pdf%3Farnumber%3D1093262&authDecision=-203>
>
>
> http://tf.nist.gov/general/pdf/1800.pdf
>
> Bruce
Additional references that estimate the degree of tank mistuning
permissable before asynchronous modes occur:

http://www.its.caltech.edu/~kaushiks/KS_RFIC.pdf
<http://www.its.caltech.edu/%7Ekaushiks/KS_RFIC.pdf>

http://www.its.caltech.edu/~kaushiks/KS_TCAS.pdf
<http://www.its.caltech.edu/%7Ekaushiks/KS_TCAS.pdf>

An early implementation:
http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA457231
<http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA457231>

Bruce
Bruce Griffiths
2011-04-10 20:24:28 UTC
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Bruce Griffiths wrote:
> Bruce Griffiths wrote:
>> Hal Murray wrote:
>>> bruce.griffiths-***@public.gmane.org said:
>>>> The 16MHz is necessary for the loop to function: The mixer mixes
>>>> down the
>>>> 26MHz to a pair of conjugate frequencies, 10MHz and 16MHz. Thermal
>>>> and
>>>> device noise is sufficient to start the process.
>>>> 10MHz = 26MHz - 16MHz
>>>> 16MHz = 26MHz - 10MHz
>>> What makes it stable at 10 and 16 MHz rather than 10.000001 and
>>> 15.999999?
>>>
>>> I'm assuming we are starting with a good 26 MHz crystal and that it
>>> would be hard to get filters that good.
>>>
>>>
>> Asynchronous modes such as 10.000001MHz plus 15.999999 MHz can be
>> problematic if the loop delay is too high.
>> http://www.femto-st.fr/~rubiola/pdf-articles/journal/1992im%28rubiola%29regenerative-divider-noise.pdf
>> <http://www.femto-st.fr/%7Erubiola/pdf-articles/journal/1992im%28rubiola%29regenerative-divider-noise.pdf>
>>
>>
>> http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F26%2F23863%2F01093262.pdf%3Farnumber%3D1093262&authDecision=-203
>> <http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel5%2F26%2F23863%2F01093262.pdf%3Farnumber%3D1093262&authDecision=-203>
>>
>>
>> http://tf.nist.gov/general/pdf/1800.pdf
>>
>> Bruce
> Additional references that estimate the degree of tank mistuning
> permissable before asynchronous modes occur:
>
> http://www.its.caltech.edu/~kaushiks/KS_RFIC.pdf
> <http://www.its.caltech.edu/%7Ekaushiks/KS_RFIC.pdf>
>
> http://www.its.caltech.edu/~kaushiks/KS_TCAS.pdf
> <http://www.its.caltech.edu/%7Ekaushiks/KS_TCAS.pdf>
>
> An early implementation:
> http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA457231
> <http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA457231>
>
>
> Bruce
>
>
If one needs a frequency comb:
http://tf.nist.gov/general/pdf/2168.pdf

Bruce
Hal Murray
2012-01-11 09:59:24 UTC
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>> The TADD-3 uses 3 AC drivers in parallel, each going through a
>> 51 ohm resistor. Changing those resistors to 150 ohms should
>> work. Maybe a bit lower to account for the impedance in the
>> drivers. I'd probably check it with a scope.


bruce.griffiths-***@public.gmane.org said:
> That approach doesn't do anything for the Vcc and GND bounce exhibited by
> the driver chip. GND and Vcc bounce is the cause of the high frequency
> ringing exhibited by the TADD-3 outputs. This ringing can even be observed
> at the outputs of inverters whose inputs are tied low or high in the same
> package

I don't see how ground bounce is going to cause ringing.

I'd expect the ringing to come from reflections from a long transmissions
line.


Anybody know what the driver in a TBolt is like? Here are 2 pictures looking
at the PPS from 2 TBolts.

This one has 10 ft of coax from one TBolt and and 25+10 ft from the other,
with no termination at the scope.
http://www.megapathdsl.net/~hmurray/time-nuts/Rigol/ring-1.png

This one has 10 ft of coax with a terminator on one side and a 10X scope
probe right at the BNC on the other.
http://www.megapathdsl.net/~hmurray/time-nuts/Rigol/ring-2.png


> Damping the crossover current induced transient in the supply leads
> (bondwire and lead frame) inductance is one way to minimise this. A small
> resistor in series with the Vcc pin often works well, the resistor value
> being chosen for near critical damping.

I'm not sure what you mean by crossover current.

I'd expect a "damping" resistor in the Vcc lead to slow down the rise time.
If you make it slow enough there won't be any ringing because the rise time
will be longer than the round trip time. Then you can treat the transmission
line as a capacitor.

I'd expect a resistor in the Vcc lead would not slow down the fall times.


If you want a slower rise time, you can also use HC rather than AC. They
probably aren't strong enough to drive a 50 ohm terminator.

Using surface mount packages reduces the inductance. (slightly?)

Another option is the bus driver chips that have multiple Vcc/GND pins.


> Another problem with the TADD-3 is the sharing of a driver chip by
> different input frequencies which leads to intermodulation between the 2
> outputs.

Yup. Job security for designers. :)

If you read the fine print in the data sheets for high speed chips, they
usually specify a marketing number with only one output changing. The good
data sheets tell you how much it slows down when multiple outputs change.


--
These are my opinions, not necessarily my employer's. I hate spam.
Bruce Griffiths
2012-01-11 11:50:35 UTC
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Hal Murray wrote:
>
>>> The TADD-3 uses 3 AC drivers in parallel, each going through a
>>> 51 ohm resistor. Changing those resistors to 150 ohms should
>>> work. Maybe a bit lower to account for the impedance in the
>>> drivers. I'd probably check it with a scope.
>>>
>
> bruce.griffiths-***@public.gmane.org said:
>
>> That approach doesn't do anything for the Vcc and GND bounce exhibited by
>> the driver chip. GND and Vcc bounce is the cause of the high frequency
>> ringing exhibited by the TADD-3 outputs. This ringing can even be observed
>> at the outputs of inverters whose inputs are tied low or high in the same
>> package
>>
> I don't see how ground bounce is going to cause ringing.
>
Some load capacitance is required (even the capacitance of a short track
on the board plus the output pin and output device capacitances will
suffice)
One of the ground bounce papers from TI will show the ringing due to
ground bounce (eg http://www.ti.com/lit/an/szza038b/szza038b.pdf).
> I'd expect the ringing to come from reflections from a long transmissions
> line.
>
Transmission line current di/dt will interact with the supply (GND or
Vcc) and output lead inductance.
>
> Anybody know what the driver in a TBolt is like? Here are 2 pictures looking
> at the PPS from 2 TBolts.
>
> This one has 10 ft of coax from one TBolt and and 25+10 ft from the other,
> with no termination at the scope.
> http://www.megapathdsl.net/~hmurray/time-nuts/Rigol/ring-1.png
>
> This one has 10 ft of coax with a terminator on one side and a 10X scope
> probe right at the BNC on the other.
> http://www.megapathdsl.net/~hmurray/time-nuts/Rigol/ring-2.png
>
>
>
The output driver is a low impedance source possibly a 74AC04M (most
likely candidate from the list of ICs used:
http://www.prc68.com/I/ThunderBolt.shtml ).
>> Damping the crossover current induced transient in the supply leads
>> (bondwire and lead frame) inductance is one way to minimise this. A small
>> resistor in series with the Vcc pin often works well, the resistor value
>> being chosen for near critical damping.
>>
> I'm not sure what you mean by crossover current.
>
During the output transition there is a short time interval (in a CMOS
inverter stage) where both the n channel and p channel devices are both
on causing a current to flow between Vcc and ground even with no
external load.
> I'd expect a "damping" resistor in the Vcc lead to slow down the rise time.
> If you make it slow enough there won't be any ringing because the rise time
> will be longer than the round trip time. Then you can treat the transmission
> line as a capacitor.
>
Thats certainly not the case in the FS730C, the risetime isnt
appreciably affected by the small (4R7) damping resistor in series with Vcc.
Adding a series damping resistor in series with the output is
insufficient to suppress ringing.
> I'd expect a resistor in the Vcc lead would not slow down the fall times.
>
>
> If you want a slower rise time, you can also use HC rather than AC. They
> probably aren't strong enough to drive a 50 ohm terminator.
>
> Using surface mount packages reduces the inductance. (slightly?)
>
> Another option is the bus driver chips that have multiple Vcc/GND pins.
>
>
GND bounce is still readily seen, the amplitude decreases somewhat but
the associated ringing frequency for a given load increases.
>
>> Another problem with the TADD-3 is the sharing of a driver chip by
>> different input frequencies which leads to intermodulation between the 2
>> outputs.
>>
> Yup. Job security for designers. :)
>
> If you read the fine print in the data sheets for high speed chips, they
> usually specify a marketing number with only one output changing. The good
> data sheets tell you how much it slows down when multiple outputs change.
>
>
>
Its not quite that simple transients are observed on quiet outputs due
to output transitions on the switching outputs.
If transitions occur simultaneously on 2 different frequency inputs
connected to the same chip then simultaneous switching effects modulate
the effective propagation delay of the output transitions.
e.g. a 1MHz output may exhibit phase modulation at 100KHz if the 1MHz
and 100KHz signals share the same output driver chip.

Bruce
Attila Kinali
2012-01-13 09:06:19 UTC
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On Thu, 12 Jan 2012 00:50:35 +1300
Bruce Griffiths <bruce.griffiths-***@public.gmane.org> wrote:

> Thats certainly not the case in the FS730C, the risetime isnt
> appreciably affected by the small (4R7) damping resistor in series with Vcc.
> Adding a series damping resistor in series with the output is
> insufficient to suppress ringing.

How about using a ferit bead into the power supply instead of a resistor?
I'm thinking about something like a BLM18. The DC resistance is much lower
while HF resistance is much higher.

Attila Kinali

--
The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
-- Tirin, The Dispossessed, U. Le Guin
Bruce Griffiths
2012-01-13 09:17:13 UTC
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Attila Kinali wrote:
> On Thu, 12 Jan 2012 00:50:35 +1300
> Bruce Griffiths<bruce.griffiths-***@public.gmane.org> wrote:
>
>
>> Thats certainly not the case in the FS730C, the risetime isnt
>> appreciably affected by the small (4R7) damping resistor in series with Vcc.
>> Adding a series damping resistor in series with the output is
>> insufficient to suppress ringing.
>>
> How about using a ferit bead into the power supply instead of a resistor?
> I'm thinking about something like a BLM18. The DC resistance is much lower
> while HF resistance is much higher.
>
> Attila Kinali
>
>
It may be useful if the ferrite bead parameters are just right.
However the bead HF resistance will increase the high frequency output
impedance in the high state which will adversely affect the high
frequency source impedance of the line driver.
Whereas a resistor increases the high state output impedance in a more
predictable way that can be easily compensated for particulalrly if a
similar resistor were used in series with the ground lead.

Bruce
s***@public.gmane.org
2012-01-11 14:59:16 UTC
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I made some tests a while ago using the PPS output from a Thunderbolt.

http://www.ko4bb.com/Test_Equipment/CoaxCableMatching.php

Didier KO4BB

Sent from my BlackBerry Wireless thingy while I do other things...

-----Original Message-----
From: Hal Murray <hmurray-8cQiHa/C+6Go9G/***@public.gmane.org>
Sender: time-nuts-bounces-***@public.gmane.org
Date: Wed, 11 Jan 2012 01:59:24
To: Discussion of precise time and frequency measurement<time-nuts-***@public.gmane.org>
Reply-To: Discussion of precise time and frequency measurement
<time-nuts-***@public.gmane.org>
Subject: Re: [time-nuts] Temperature and signal amp for 'Bay FE-5680A?


>> The TADD-3 uses 3 AC drivers in parallel, each going through a
>> 51 ohm resistor. Changing those resistors to 150 ohms should
>> work. Maybe a bit lower to account for the impedance in the
>> drivers. I'd probably check it with a scope.


bruce.griffiths-***@public.gmane.org said:
> That approach doesn't do anything for the Vcc and GND bounce exhibited by
> the driver chip. GND and Vcc bounce is the cause of the high frequency
> ringing exhibited by the TADD-3 outputs. This ringing can even be observed
> at the outputs of inverters whose inputs are tied low or high in the same
> package

I don't see how ground bounce is going to cause ringing.

I'd expect the ringing to come from reflections from a long transmissions
line.


Anybody know what the driver in a TBolt is like? Here are 2 pictures looking
at the PPS from 2 TBolts.

This one has 10 ft of coax from one TBolt and and 25+10 ft from the other,
with no termination at the scope.
http://www.megapathdsl.net/~hmurray/time-nuts/Rigol/ring-1.png

This one has 10 ft of coax with a terminator on one side and a 10X scope
probe right at the BNC on the other.
http://www.megapathdsl.net/~hmurray/time-nuts/Rigol/ring-2.png


> Damping the crossover current induced transient in the supply leads
> (bondwire and lead frame) inductance is one way to minimise this. A small
> resistor in series with the Vcc pin often works well, the resistor value
> being chosen for near critical damping.

I'm not sure what you mean by crossover current.

I'd expect a "damping" resistor in the Vcc lead to slow down the rise time.
If you make it slow enough there won't be any ringing because the rise time
will be longer than the round trip time. Then you can treat the transmission
line as a capacitor.

I'd expect a resistor in the Vcc lead would not slow down the fall times.


If you want a slower rise time, you can also use HC rather than AC. They
probably aren't strong enough to drive a 50 ohm terminator.

Using surface mount packages reduces the inductance. (slightly?)

Another option is the bus driver chips that have multiple Vcc/GND pins.


> Another problem with the TADD-3 is the sharing of a driver chip by
> different input frequencies which leads to intermodulation between the 2
> outputs.

Yup. Job security for designers. :)

If you read the fine print in the data sheets for high speed chips, they
usually specify a marketing number with only one output changing. The good
data sheets tell you how much it slows down when multiple outputs change.


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Hal Murray
2012-02-16 08:20:56 UTC
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Here is a graph to follow up that event.
http://www.megapathdsl.net/~hmurray/time-nuts/Dropout-Feb-11-12-2012.png

The green/red lines on the bottom are the good/bad results from the GPRMC
sentence each second.

The blue/purple lines on top are the number of satellites. "good" means it
had a number in the SNR slot vs empty for "bad".

The unit is inside my house. I'm in Menlo Park, 94025, the fringe of Silicon
Valley. There is probably lots of multi-path from my neighbors house and
lots of attenuation from the big tree out front/south-east.

The good slots are plotted slightly above the nominal line and the bad are
slightly below so they are both visible if they would land on top of each
other.

I can provide the raw data if anybody wants to investigate more.

Does anybody know if the FCC wants data like this and if so do you have a
contact?


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Jim Palfreyman
2012-02-16 10:56:24 UTC
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Lightsquared doing their final test run...

Jim
Hal Murray
2012-04-12 21:17:32 UTC
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hmurray-8cQiHa/C+6Go9G/***@public.gmane.org said:
> I think you will just get the position of the receiving antenna for the
> repeater. It will get the time when the signals arrived at that antenna.

> Consider what happens if you replace the air between the repeater's transmit
> antenna and the GPS receiver with a chunk of coax. The key idea is that
> the signals from each satellite are delayed the same amount with either a
> repeater or coax.

Argh. I hate it when I'm thinking one thing and type the opposite.

The GPS-repeater receiver will see the time at the receiving antenna for the
repeater as delayed by the propagation from repeater to GPS receiver. You
get the right answer if you think of that air path as coax.



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Hal Murray
2012-12-18 07:21:17 UTC
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>> Cond. Material Magnet Wire Helix
>> (What is "magnet wire", and what does "helix" mean and how does it effect
>> coax?)

> Magnet wire is enamelled wire (usually copper).

I'm familiar with that usage, but I don't know why it's interesting in the
context of coax.

I think the key idea is that the insulation is thin so you can get lots of
turns/inch in a transformer.

I don't understand what a "helix" is in coax, or rather I don't appreciate
the numbers. I'd guess that the "center conductor" is constructed as a helix
and that increases the inductance/meter by a whole lot, or something like
that. But isn't there a sqrt in there?


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Jim Lux
2012-12-18 14:05:44 UTC
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On 12/17/12 11:21 PM, Hal Murray wrote:
>>> Cond. Material Magnet Wire Helix
>>> (What is "magnet wire", and what does "helix" mean and how does it effect
>>> coax?)
>
>> Magnet wire is enamelled wire (usually copper).
>
> I'm familiar with that usage, but I don't know why it's interesting in the
> context of coax.
>
> I think the key idea is that the insulation is thin so you can get lots of
> turns/inch in a transformer.
>
> I don't understand what a "helix" is in coax, or rather I don't appreciate
> the numbers. I'd guess that the "center conductor" is constructed as a helix
> and that increases the inductance/meter by a whole lot, or something like
> that. But isn't there a sqrt in there?


That is exactly what is done.. a *very tiny* wire is wound in a helix
around a core (sometimes ferrous) that forms the center conductor of the
coaxial cable, so it has huge L per length.

And yes, 1/sqrt(LC) is the propagation velocity

>
>
Hal Murray
2013-01-22 04:04:57 UTC
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> Heliax is a type/brand of coax not an antenna.


Ahh. Thanks. Everything makes sense now.

I was thinking of Helix from Jim's recent comments rather than Heliax.


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Hal Murray
2013-09-29 22:33:22 UTC
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> Each ntpd refclock has a 64 slot FIFO. Every polling interval, ntpd
> processes the data in the buffer and turns it into a sample feed to the main
> algorithm. That processing discards 1/3 of the samples as (potential)
> outliers and averages the rest.

Rats. I left out a critical step.

Every second the shm refclock driver checks the shared memory slot for new
data. (I's say "polls", but that gets confused with the polling interval
that min/maxpoll sets.)



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Hal Murray
2014-02-06 22:04:57 UTC
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> The software is a simple python hack. It runs on Linux.
> http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/pps.py

Sigh. That's not the right code. I've deleted it to avoid confusion.

The code I was trying to point to is:
http://www.megapathdsl.net/~hmurray/time-nuts/60Hz/60Hz.py


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Hal Murray
2015-07-25 23:25:33 UTC
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I've updated the graph at:
http://www.megapathdsl.net/~hmurray/time-nuts/line/Calif-60Hz-2014-2015.pn
g

and added July-2015 at:
http://www.megapathdsl.net/~hmurray/time-nuts/line/Calif-60Hz-2015-Jul.png

July 19th shifted 15 seconds in one day!
The shift is 25 seconds over July 17-19.

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Bob Camp
2015-07-26 12:08:00 UTC
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Hi

That correlates quite well with data from the 1960’s before “everybody” was
on one big network.

Bob

> On Jul 25, 2015, at 7:25 PM, Hal Murray <***@megapathdsl.net> wrote:
>
>
> I've updated the graph at:
> http://www.megapathdsl.net/~hmurray/time-nuts/line/Calif-60Hz-2014-2015.pn
> g
>
> and added July-2015 at:
> http://www.megapathdsl.net/~hmurray/time-nuts/line/Calif-60Hz-2015-Jul.png
>
> July 19th shifted 15 seconds in one day!
> The shift is 25 seconds over July 17-19.
>
> --
> These are my opinions. I hate spam.
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-***@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.

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Bill Byrom
2015-07-26 18:25:54 UTC
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There have been a number of proposals to completely eliminate manual
time correction (used to keep synchronous clocks accurate over long time
periods). There apparently was a manual procedure activated when the
error reached +/- 30 seconds from true time, but I think that since 2011
the power grid reliability considerations have caused grid operators to
not make any frequency changes for clock time correction. Frequency
changes are often made to change the power transfer rate.

See: FERC Docket RM14-10-000 Order: Real Power Balancing Control
Performance Reliability Standard (issued April 16, 2015) - this doesn't
mention use of time error correction!
http://www.ferc.gov/whats-new/comm-meet/2015/041615/E-3.PDF

FERC docket RM09-13-000: Time Error Correction Reliability Standard
http://www.balch.com/files/upload/%284-24-2010%29%20NERC_BAL-004_NOPR_Comments.pdf
In October 2012 this petition was withdrawn.

60Hz Stability on Power Grid Going Away?
http://www.radiomagonline.com/deep-dig/0005/60hz-stability-on-power-grid-going-away/33527

NERC Frequency Response Standard Background Document
http://www.nerc.com/comm/oc/rs%20landing%20page%20dl/related%20files/bal-003-1_background_document_clean_20121130.pdf

It appears from various comments that with no manual time correction,
the accumulated time error in the East Interconnection will typically
gain 20+ minutes/year. The West will gain 8 minutes/year and ERCOT
(Texas area) will gain 2 minutes/year.
http://www.ercot.com/content/meetings/rms/keydocs/2011/0518/03_manual_time_error_correction_elimination_field_trial.doc

So don't trust an AC synchronous motor clock in North America.

--
Bill Byrom N5BB



On Sun, Jul 26, 2015, at 07:08 AM, Bob Camp wrote:
> Hi
>
> That correlates quite well with data from the 1960’s before “everybody”
> was
> on one big network.
>
> Bob
>
>> On Jul 25, 2015, at 7:25 PM, Hal Murray <***@megapathdsl.net> wrote:
>>
>>
>> I've updated the graph at:
>> http://www.megapathdsl.net/~hmurray/time-nuts/line/Calif-60Hz-2014-2015.pn
>> g
>>
>> and added July-2015 at:
>> http://www.megapathdsl.net/~hmurray/time-nuts/line/Calif-60Hz-2015-Jul.png
>>
>> July 19th shifted 15 seconds in one day!
>> The shift is 25 seconds over July 17-19.
>>
>> --
>> These are my opinions.  I hate spam.
>>
>>
>>
>> _________________________________________________
>> time-nuts mailing list -- time-***@febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>
> _________________________________________________
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Dave Martindale
2015-07-27 00:08:41 UTC
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It's not just synchronous-motor clocks that use line frequency as a time
reference. I have a Heathkit alarm clock that counts cycles of line
frequency as its timebase. I think that was common in the early
generations of NMOS clock chips. The clock does have a backup oscillator
(powered by a 9 V battery) for use when line voltage disappears, but its
accuracy is horrible. I think it's an RC oscillator, and in a power
failure of a few hours it will accumulate minutes of time error.

So a bunch of people with analog and digital clocks from that era are
likely to notice the drift, particularly at 20 minutes/year.

When did 32 kHz crystals get cheap enough that line-powered clocks started
using them as a time reference instead of counting line cycles?

- Dave

On Sun, Jul 26, 2015 at 2:25 PM, Bill Byrom <***@radio.sent.com> wrote:

>
> 60Hz Stability on Power Grid Going Away?
>
> http://www.radiomagonline.com/deep-dig/0005/60hz-stability-on-power-grid-going-away/33527
>
> NERC Frequency Response Standard Background Document
>
> http://www.nerc.com/comm/oc/rs%20landing%20page%20dl/related%20files/bal-003-1_background_document_clean_20121130.pdf
>
> It appears from various comments that with no manual time correction,
> the accumulated time error in the East Interconnection will typically
> gain 20+ minutes/year. The West will gain 8 minutes/year and ERCOT
> (Texas area) will gain 2 minutes/year.
>
> http://www.ercot.com/content/meetings/rms/keydocs/2011/0518/03_manual_time_error_correction_elimination_field_trial.doc
>
> So don't trust an AC synchronous motor clock in North America.
>
> --
> Bill Byrom N5BB
>
>
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Bill Byrom
2015-07-27 04:31:05 UTC
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In the early 1970's both LED and LSI integrated circuit technology
advanced to the point that digital wristwatches were introduced. These
used 32,768 Hz crystals. Use of this technology was made in digital desk
clocks (such as alarm radio clocks), but I think that for many years it
was much less expensive to use the AC line as a frequency standard.
Early Mostek clock IC's used the 50/60 Hz powerline as the reference and
didn't include provisions for a crystal.

The first digital clock I owned was a flip card clock radio in around
1970. An AC line powered synchronous motor slowly flipped minute and
hour cards. A few years later I had a Radio Shack LED wristwatch.

I see that 32,768 Hz crystals can now be purchased for US $0.15 each in
lots of 100.

--
Bill Byrom N5BB



On Sun, Jul 26, 2015, at 07:08 PM, Dave Martindale wrote:
> It's not just synchronous-motor clocks that use line frequency as a time
> reference.  I have a Heathkit alarm clock that counts cycles of line
> frequency as its timebase.  I think that was common in the early
> generations of NMOS clock chips.  The clock does have a backup oscillator
> (powered by a 9 V battery) for use when line voltage disappears, but its
> accuracy is horrible.  I think it's an RC oscillator, and in a power
> failure of a few hours it will accumulate minutes of time error.
>
> So a bunch of people with analog and digital clocks from that era are
> likely to notice the drift, particularly at 20 minutes/year.
>
> When did 32 kHz crystals get cheap enough that line-powered clocks
> started
> using them as a time reference instead of counting line cycles?
>
> - Dave
>
> On Sun, Jul 26, 2015 at 2:25 PM, Bill Byrom <***@radio.sent.com> wrote:
>
>>
>> 60Hz Stability on Power Grid Going Away?
>>
>> http://www.radiomagonline.com/deep-dig/0005/60hz-stability-on-power-grid-going-away/33527
>>
>> NERC Frequency Response Standard Background Document
>>
>> http://www.nerc.com/comm/oc/rs%20landing%20page%20dl/related%20files/bal-003-1_background_document_clean_20121130.pdf
>>
>> It  appears from various comments that with no manual time correction,
>> the accumulated time error in the East Interconnection will typically
>> gain 20+ minutes/year. The West will gain 8 minutes/year and ERCOT
>> (Texas area) will gain 2 minutes/year.
>>
>> http://www.ercot.com/content/meetings/rms/keydocs/2011/0518/03_manual_time_error_correction_elimination_field_trial.doc
>>
>> So don't trust an AC synchronous motor clock in North America.
>>
>> --
>> Bill Byrom N5BB
>>
>>
> _________________________________________________
> time-nuts mailing list -- time-***@febo.com
> To unsubscribe, go to
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Bob Camp
2015-07-27 10:55:17 UTC
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Hi

The utility of the watch crystal is greatly enhanced in a wrist watch by
the calibration process on the watch. When they use one in an AC powered
clock (say a clock / radio / alarm) , it’s as a backup device. Power goes out
and the crystal keeps time. They don’t do much (any at all) calibration in this
application. The resultant time error is “ok” for an hour or so. It would be
really objectionable over a week or a month.

Bob

> On Jul 27, 2015, at 12:31 AM, Bill Byrom <***@radio.sent.com> wrote:
>
> In the early 1970's both LED and LSI integrated circuit technology
> advanced to the point that digital wristwatches were introduced. These
> used 32,768 Hz crystals. Use of this technology was made in digital desk
> clocks (such as alarm radio clocks), but I think that for many years it
> was much less expensive to use the AC line as a frequency standard.
> Early Mostek clock IC's used the 50/60 Hz powerline as the reference and
> didn't include provisions for a crystal.
>
> The first digital clock I owned was a flip card clock radio in around
> 1970. An AC line powered synchronous motor slowly flipped minute and
> hour cards. A few years later I had a Radio Shack LED wristwatch.
>
> I see that 32,768 Hz crystals can now be purchased for US $0.15 each in
> lots of 100.
>
> --
> Bill Byrom N5BB
>
>
>
> On Sun, Jul 26, 2015, at 07:08 PM, Dave Martindale wrote:
>> It's not just synchronous-motor clocks that use line frequency as a time
>> reference. I have a Heathkit alarm clock that counts cycles of line
>> frequency as its timebase. I think that was common in the early
>> generations of NMOS clock chips. The clock does have a backup oscillator
>> (powered by a 9 V battery) for use when line voltage disappears, but its
>> accuracy is horrible. I think it's an RC oscillator, and in a power
>> failure of a few hours it will accumulate minutes of time error.
>>
>> So a bunch of people with analog and digital clocks from that era are
>> likely to notice the drift, particularly at 20 minutes/year.
>>
>> When did 32 kHz crystals get cheap enough that line-powered clocks
>> started
>> using them as a time reference instead of counting line cycles?
>>
>> - Dave
>>
>> On Sun, Jul 26, 2015 at 2:25 PM, Bill Byrom <***@radio.sent.com> wrote:
>>
>>>
>>> 60Hz Stability on Power Grid Going Away?
>>>
>>> http://www.radiomagonline.com/deep-dig/0005/60hz-stability-on-power-grid-going-away/33527
>>>
>>> NERC Frequency Response Standard Background Document
>>>
>>> http://www.nerc.com/comm/oc/rs%20landing%20page%20dl/related%20files/bal-003-1_background_document_clean_20121130.pdf
>>>
>>> It appears from various comments that with no manual time correction,
>>> the accumulated time error in the East Interconnection will typically
>>> gain 20+ minutes/year. The West will gain 8 minutes/year and ERCOT
>>> (Texas area) will gain 2 minutes/year.
>>>
>>> http://www.ercot.com/content/meetings/rms/keydocs/2011/0518/03_manual_time_error_correction_elimination_field_trial.doc
>>>
>>> So don't trust an AC synchronous motor clock in North America.
>>>
>>> --
>>> Bill Byrom N5BB
>>>
>>>
>> _________________________________________________
>> time-nuts mailing list -- time-***@febo.com
>> To unsubscribe, go to
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Bill Hawkins
2015-07-27 04:37:20 UTC
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Gotta get some answers from my relative in a PA gas fired plant. A year
ago he told me that the plan to deregulate the number of cycles in a day
had been abandoned. The referenced documents are older than that.

OTOH, there's no other explanation for Hal Murray's observation of the
West Coast grid variation.

Seems to me that all of the rotating synchronous machinery connected to
a grid is constrained by all of that heavy rotating machinery to change
speed quite slowly, like starting to change the direction of a ship
heading to a port about 5 miles out.

There are at least three grids in the US that are independent of each
other in frequency. That reduces the strains on a grid from distant
changes. Power is transferred using high voltage DC transmission lines.
Really large solid state inverters convert between AC and DC. Each
inverter can make any frequency it wants to, subject to the constraints
of all that synchronous machinery.

Frankly, I'm puzzled by the graphs that relate to the time offset. All
that's available to the observer is the line frequency. Relative time
may be inferred with a cycle counter. How is that counter set to UTC?
How can you tell the difference between time error from some reference
point, and cycles gained or lost in the counting equipment - due to
noise and/or computer interrupt servicing routines?

When I asked for data from parts of the country east of the Rockies (on
7/10), I got one reply from a person who is not a member of the list but
reads archive sites. He sent his long term graph for Texas and the link
to a real-time statistics page that gave him the data for the graph.

The statistics are at (strip the stuff after com/ to get the home page
and further details):

http://www.ercot.com/content/cdr/html/real_time_system_conditions.html

His chart (with permission) is at:

http://home.earthlink.net/~schultdw/power/all.png

In this case, the time reference was given by the power company. No
cycles were counted.

Regards,
Bill Hawkins

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Hal Murray
2016-04-11 08:22:48 UTC
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***@xtra.co.nz said:
> There is a proposal to use multiple light bucket style optical telescopes to
> do Intensity stellar Interferometry over short baselines (up to perhaps 1km 
> or so) by using independent clocks to time tag photon  arrivals.

> The relative positions of the telescopes has to be known to within a cm or
> so for this to work.

My guess is that survey grade GPS is going to be your straw man. You might
ask your local surveyors what they charge for that level of accuracy.

Do you have line of sight? How good are surveyor's distance measuring setups?

The VLBI guys look at a strong signal and back compute the antenna location.
That may work better if you have more than 2 telescopes. The Earth is
rotating so the time offset changes with Cos some magic angle. Don't forget
Earth tides.



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Hal Murray
2016-05-28 01:58:35 UTC
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***@xtra.co.nz said:
> All the filtering and down mixing is done in the digital domain.
> Anitialiasing filters in front of the ADCs are also be required.

What sort of bandwidth is expected?

The usual trick with audio ADCs is to have a low cost analog filter that
does't have a sharp corner but lets everything you want through, sample at a
high rate - say 16x, run that through a digital filter with a sharp cutoff,
then decimate down to the desired sample rate.

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Bruce Griffiths
2016-05-28 03:08:04 UTC
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The Red Pitaya FPGA may be a little too small.Its not clear if a single chip ADC is used.If not, the performance will suffer.Dc coupled inputs will degrade the performance somewhat compared to transformer coupled inputs.

Input bandwidth would be around 40MHz or so for the Nyquist band of interest.The output bandwidth used was something like 100 kHz.
Bruce


On Saturday, 28 May 2016 2:01 PM, Hal Murray <***@megapathdsl.net> wrote:



***@xtra.co.nz said:
> All the filtering and down mixing is done in the digital domain.
> Anitialiasing filters in front of the ADCs are also be required.

What sort of bandwidth is expected?

The usual trick with audio ADCs is to have a low cost analog filter that
does't have a sharp corner but lets everything you want through, sample at a
high rate - say 16x, run that through a digital filter with a sharp cutoff,
then decimate down to the desired sample rate.

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Bruce Griffiths
2016-05-28 04:52:44 UTC
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The first version of the Red Pitaya apparently used an  LTC2145 dual input 14 bit ADC with an SNR of around 72dB (11.6 bits) or so. Various claims of 10 bits effective implies that poor layout, and/or a noisy sampling clock, and/or the analog front end degrade the performance somewhat. For this particular application a noisy sampling clock may  be less of an issue as it is common to both ADC channels.
The Red Pitaya FPGA has about 1/2 the number of logic cells of the FPGA used in the Ettus 210 used in the paper.
The internal sampling jitter of the Ltc2145 appears to be somewhat lower than that of the TI ADC used in the ETTUS 210 SDR.

Bruce


On Saturday, 28 May 2016 3:08 PM, Bruce Griffiths <***@xtra..co.nz> wrote:


The Red Pitaya FPGA may be a little too small.Its not clear if a single chip ADC is used.If not, the performance will suffer.Dc coupled inputs will degrade the performance somewhat compared to transformer coupled inputs.

Input bandwidth would be around 40MHz or so for the Nyquist band of interest.The output bandwidth used was something like 100 kHz.
Bruce


    On Saturday, 28 May 2016 2:01 PM, Hal Murray <***@megapathdsl.net> wrote:



***@xtra.co.nz said:
> All the filtering and down mixing is done in the digital domain.
> Anitialiasing filters in front of the ADCs are also be required.

What sort of bandwidth is expected?

The usual trick with audio ADCs is to have a low cost analog filter that
does't have a sharp corner but lets everything you want through, sample at a
high rate - say 16x, run that through a digital filter with a sharp cutoff,
then decimate down to the desired sample rate.

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Bob Camp
2016-05-28 11:55:28 UTC
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Hi

The normal process with a 10 Hz beat note in a DMTD is to have something like a 6 Hz two
pole high pass and a 15 Hz two pole lowpass after the mixer and before any zero crossing stuff.
This is after down conversion, but before any demodulation. This of course is based on the
fundamental assumption in a DMTD that the inputs are within a fraction of a Hertz of the target
at all times. In a system that has one input offset 12 to 121 Hz and the other at 80 to 9,000 Hz,
the approach isn’t going to work as well.

Bob

> On May 27, 2016, at 9:58 PM, Hal Murray <***@megapathdsl.net> wrote:
>
>
> ***@xtra.co.nz said:
>> All the filtering and down mixing is done in the digital domain.
>> Anitialiasing filters in front of the ADCs are also be required.
>
> What sort of bandwidth is expected?
>
> The usual trick with audio ADCs is to have a low cost analog filter that
> does't have a sharp corner but lets everything you want through, sample at a
> high rate - say 16x, run that through a digital filter with a sharp cutoff,
> then decimate down to the desired sample rate.
>
> --
> These are my opinions. I hate spam.
>
>
>
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jimlux
2016-05-28 13:16:46 UTC
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On 5/27/16 6:58 PM, Hal Murray wrote:
>
> ***@xtra.co.nz said:
>> All the filtering and down mixing is done in the digital domain.
>> Anitialiasing filters in front of the ADCs are also be required.
>
> What sort of bandwidth is expected?
>
> The usual trick with audio ADCs is to have a low cost analog filter that
> does't have a sharp corner but lets everything you want through, sample at a
> high rate - say 16x, run that through a digital filter with a sharp cutoff,
> then decimate down to the desired sample rate.
>

The USRP uses fast ADCs intended for the wireless market. Sample rates
are >50MSPS. You can get daughter cards which have an analog PLL and
mixer to tune over a wider band - as you can imagine, 2.5 and 5.8 GHz
are popular.


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Bob Stewart
2016-05-28 05:05:39 UTC
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Hi Bruce,

What about the BeMicroCV-A9 that Scotty Cowling has been recommending in QEX? It has a Cyclone V SoC FPGA running at 800MHz. Installments to his series have been slow coming, but I've been wondering if this could be the basis for a Timepod type of unit.

Bob

--------------------------------------------
On Fri, 5/27/16, Bruce Griffiths <***@xtra.co.nz> wrote:

Subject: Re: [time-nuts] Commercial software defined radio for clock metrology
To: "Discussion of precise time and frequency measurement" <time-***@febo.com>
Date: Friday, May 27, 2016, 10:08 PM

The Red Pitaya FPGA may
be a little too small.Its not clear if a single chip ADC is
used.If not, the performance will suffer.Dc coupled inputs
will degrade the performance somewhat compared to
transformer coupled inputs.

Input bandwidth would be around 40MHz or so for
the Nyquist band of interest.The output bandwidth used was
something like 100 kHz.
Bruce


    On
Saturday, 28 May 2016 2:01 PM, Hal Murray <***@megapathdsl.net>
wrote:




***@xtra.co.nz
said:
> All the filtering and down mixing
is done in the digital domain.
>
Anitialiasing filters in front of the ADCs are also be
required.

What sort of
bandwidth is expected?

The
usual trick with audio ADCs is to have a low cost analog
filter that
does't have a sharp corner
but lets everything you want through, sample at a
high rate - say 16x, run that through a digital
filter with a sharp cutoff,
then decimate
down to the desired sample rate.

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Bruce Griffiths
2016-05-28 08:36:16 UTC
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The FPGA is probably adequate (if it has LVDS inputs), but a dual single chip ADC is also required.
Bruce


On Saturday, 28 May 2016 5:05 PM, Bob Stewart <***@evoria.net> wrote:


Hi Bruce,

What about the BeMicroCV-A9 that Scotty Cowling has been recommending in QEX?  It has a Cyclone V SoC FPGA running at 800MHz.  Installments to his series have been slow coming, but I've been wondering if this could be the basis for a Timepod type of unit.

Bob

--------------------------------------------
On Fri, 5/27/16, Bruce Griffiths <***@xtra.co.nz> wrote:

Subject: Re: [time-nuts] Commercial software defined radio for    clock    metrology
To: "Discussion of precise time and frequency measurement" <time-***@febo..com>
Date: Friday, May 27, 2016, 10:08 PM

The Red Pitaya FPGA may
be a little too small.Its not clear if a single chip ADC is
used.If not, the performance will suffer.Dc coupled inputs
will degrade the performance somewhat compared to
transformer coupled inputs.

Input bandwidth would be around 40MHz or so for
the Nyquist band of interest.The output bandwidth used was
something like 100 kHz.
Bruce
 

    On
Saturday, 28 May 2016 2:01 PM, Hal Murray <***@megapathdsl.net>
wrote:
 



***@xtra.co.nz
said:
> All the filtering and down mixing
is done in the digital domain.
>
Anitialiasing filters in front of the ADCs are also be
required.

What sort of
bandwidth is expected?

The
usual trick with audio ADCs is to have a low cost analog
filter that
does't have a sharp corner
but lets everything you want through, sample at a
high rate - say 16x, run that through a digital
filter with a sharp cutoff,
then decimate
down to the desired sample rate.

--
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hate spam.



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Hal Murray
2016-06-05 05:50:14 UTC
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***@xtra.co.nz said:
> More likely the missing GPS receiver board is installed over the ground
> plane.

There is a small metal shield in the upper right with some coax coming out of
it. It says FURUNO. They make GPS stuff.

Google finds:
http://www.furuno.com/en/products/gnss-module/GT-8031

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Hal Murray
2016-09-20 21:58:08 UTC
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***@xtra.co.nz said:
>> It is possible to check the output level without an oscilloscope ?
> Only with a clasical (diode detector) RF probe (they're still available) or
> an RF power meter.

How about a diode, small cap, and a DC meter? (and a few clip leads)


It won't give an accurate reading, but it should be good enough to detect a
busted cap.


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Hal Murray
2017-02-22 08:54:34 UTC
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***@xtra.co.nz said:
> If you have a dark fiber or 2 between the surface and the lab and a pair of
> sufficiently stable lasers (one at the surface and one in the underground
> lab) you could look at the change in beat frequency between the lasers
> (around 50Hz for a pair of red lasers).

Interesting idea. Thanks.

How stable is a good laser and/or how hard do I have to work (or how much do
I have to pay) to get one stable enough for this experiment? What's the line
width on a typical laser? How much does it wander with temperature and
supply voltage and phase of the moon?


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Hal Murray
2017-06-07 10:18:18 UTC
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Argh/sorry. I fatfingered something. Wrong list.


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Hal Murray
2017-07-24 17:02:42 UTC
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[Correcting my earlier comment.]
> You could probably add a diode to make it work.

It takes more than just a diode.

The voltage on the modem control signals is probably too high. You will also
need some way to drop it to what the chip expects, probably 5 volts. Simple
3 pin regulators need input and output caps. There is probably one already
on the output side.

The just-a-diode from a message early in this thread works because the LM358
op-amp can take a higher supply voltage.


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Paul Alfille
2017-07-26 01:19:37 UTC
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Here are front and back pictures.



On Mon, Jul 24, 2017 at 1:02 PM, Hal Murray <***@megapathdsl.net> wrote:

> [Correcting my earlier comment.]
> > You could probably add a diode to make it work.
>
> It takes more than just a diode.
>
> The voltage on the modem control signals is probably too high. You will
> also
> need some way to drop it to what the chip expects, probably 5 volts.
> Simple
> 3 pin regulators need input and output caps. There is probably one already
> on the output side.
>
> The just-a-diode from a message early in this thread works because the
> LM358
> op-amp can take a higher supply voltage.
>
>
> --
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>
>
>
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Hal Murray
2017-08-19 21:38:11 UTC
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> The REF 0 side is still sane.

Argh. REF 0 has the same problem, but the ntpd that is looking at it is
happy. I can't find the fixup code.


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Adrian Godwin
2017-08-21 14:10:45 UTC
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Is it the KS24361 code itself or the GPS receiver in it sending nonsense ?


On Sat, Aug 19, 2017 at 10:38 PM, Hal Murray <***@megapathdsl.net>
wrote:

> > The REF 0 side is still sane.
>
> Argh. REF 0 has the same problem, but the ntpd that is looking at it is
> happy. I can't find the fixup code.
>
>
> --
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>
>
>
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Mark Sims
2017-08-21 16:46:13 UTC
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I think these work like the Z801A where you can turn off the unit, disconnect the antenna, power up, set the date (and time?), re-connect the antenna, and it should should recover and remember the date correction.
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Hal Murray
2018-03-05 00:59:52 UTC
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Bruce Griffiths <***@xtra.co.nz> said:
> If I had a suitable PCB board for it I would do the measurement properly.

What would a suitable board look like and/or what sort of gear do you need to
measure PN?


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Bob kb8tq
2018-03-05 01:19:24 UTC
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Hi

The “best” way to measure phase noise will always be a “that depends” sort of thing. One
pretty darn good way to check noise on any amplifier is to use something like a TimePod.
You use a power splitter and a pretty good source. First you check your TImePod (or whatever)
for floor. You then stick the amp in one leg. You re-measure phase noise (or ADEV). Assuming
it comes up above the previous floor, you have your number for the device. If it does not come
up above the previous floor, you need a different test set.

Bob

> On Mar 4, 2018, at 7:59 PM, Hal Murray <***@megapathdsl.net> wrote:
>
> Bruce Griffiths <***@xtra.co.nz> said:
>> If I had a suitable PCB board for it I would do the measurement properly.
>
> What would a suitable board look like and/or what sort of gear do you need to
> measure PN?
>
>
> --
> These are my opinions. I hate spam.
>
>
>
> _______________________________________________
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Bruce Griffiths
2018-03-05 01:32:56 UTC
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Since I have a Timepod all that I'd need would be a board that had SMA inputs and outputs with provision for an LC L network to step up the input if necessary plus an RLC network on the output something like in the attachment.

If one doesnt have a Timepod or equivalent a low noise phase detector will suffice for the noisier sources. An adjustable phase shift network is required to achieve quadrature between the LO (driven directly from the splitter) and the RF input (driven by the DUT output).

The required phase shift adjustment range could perhaps be reduced by using a quadrature hybrid to split the test source instead of a standard splitter. The output of the phase detector is low pass filtered and amplified and fed to a high resolution ADC such as a sound card.

Bruce

>
> On 05 March 2018 at 13:59 Hal Murray <***@megapathdsl.net> wrote:
>
> Bruce Griffiths <***@xtra.co.nz> said:
>
> > >
> > If I had a suitable PCB board for it I would do the measurement properly.
> >
> > >
> What would a suitable board look like and/or what sort of gear do you need to
> measure PN?
>
> --
> These are my opinions. I hate spam.
>
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Bob kb8tq
2018-03-05 02:17:45 UTC
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Hi

Having tried to do these measurements a lot of ways ….. the TimePod makes it *very*
easy. The ability to get phase noise and ADEV “all at once” is part of it. The ability to
handle a wide range of input levels with minimal degradation is a also part of the why.
The software makes it easy for lazy Bob … a big plus ….

Bob

> On Mar 4, 2018, at 8:32 PM, Bruce Griffiths <***@xtra.co.nz> wrote:
>
> Since I have a Timepod all that I'd need would be a board that had SMA inputs and outputs with provision for an LC L network to step up the input if necessary plus an RLC network on the output something like in the attachment.
>
> If one doesnt have a Timepod or equivalent a low noise phase detector will suffice for the noisier sources. An adjustable phase shift network is required to achieve quadrature between the LO (driven directly from the splitter) and the RF input (driven by the DUT output).
>
> The required phase shift adjustment range could perhaps be reduced by using a quadrature hybrid to split the test source instead of a standard splitter. The output of the phase detector is low pass filtered and amplified and fed to a high resolution ADC such as a sound card.
>
> Bruce
>
>>
>> On 05 March 2018 at 13:59 Hal Murray <***@megapathdsl.net> wrote:
>>
>> Bruce Griffiths <***@xtra.co.nz> said:
>>
>>>>
>>> If I had a suitable PCB board for it I would do the measurement properly.
>>>
>>>>
>> What would a suitable board look like and/or what sort of gear do you need to
>> measure PN?
>>
>> --
>> These are my opinions. I hate spam.
>>
>> _______________________________________________
>> time-nuts mailing list -- time-***@febo.com
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>>
> <CMOS_PN_test.PNG>_______________________________________________
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ewkehren via time-nuts
2018-03-05 09:22:12 UTC
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BruceWisjh I had known about it a week ago and we could have added a board to the A9 order. Next order is probably three weeks away ifIi can help contact me off list     Bert Kehren
Sent from my Galaxy Tab® A
-------- Original message --------From: Bruce Griffiths <***@xtra.co.nz> Date: 3/4/18 8:32 PM (GMT-05:00) To: Hal Murray <***@megapathdsl.net>, Discussion of precise time and frequency measurement <time-***@febo.com> Subject: Re: [time-nuts] LT1016 as a pulse shaper...
Since I have a Timepod all that I'd need would be a board that had SMA inputs and outputs with provision for an LC L network to  step up the input if necessary plus an RLC network on the output something like in the attachment.

If one doesnt have a Timepod or equivalent a low noise phase detector will suffice for the noisier sources. An adjustable phase shift network is required to achieve quadrature between the LO (driven directly from the splitter) and the RF input (driven by the DUT output).

The required phase shift adjustment range could perhaps be reduced by using a quadrature hybrid to split the test source instead of a standard splitter. The output of the phase detector is low pass filtered and amplified and fed to a high resolution ADC such as a sound card.

Bruce

>
>     On 05 March 2018 at 13:59 Hal Murray <***@megapathdsl.net> wrote:
>
>     Bruce Griffiths <***@xtra.co.nz> said:
>
>         > >
> >         If I had a suitable PCB board for it I would do the measurement properly.
> >
> >     >
>     What would a suitable board look like and/or what sort of gear do you need to
>     measure PN?
>
>     --
>     These are my opinions. I hate spam.
>
>     _______________________________________________
>     time-nuts mailing list -- time-***@febo.com
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Hal Murray
2018-05-18 07:09:43 UTC
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> It's not hard to make your own plots. This is from 66 38' north.
> http://users.megapathdsl.net/~hmurray/time-nuts/Arctic/Polar-A.png
> If anybody wants to play, I'll put the code on the web.

Code is on:
http://users.megapathdsl.net/~hmurray/time-nuts/Arctic/code/


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