Discussion:
Advice on sighting a roof mounted gps area please
(too old to reply)
swingbyte
2014-10-12 11:34:52 UTC
Permalink
Hi All,
I am building a house extension and part of the works involves adding a
new hip roof made of corrugated iron. I was thinking I would pass a
50mm pvc pipe through the roof with a tee and then mount two conical gps
timing antennas on top of it. I am in a low point and don't have
visibility of the horizons ( I'm not in the out-back).
My question is should I mount on the peak of the roof? How close can I
mount two antennas from each other? Can they interfere with each other?
I am also in the midst of some tall trees - although my new roof will be
pretty high it will still be below the tallest trees.
Of course the main reason for this is I want to do some accurate timing

ASCII art of proposed set-up

A A
| |
--------------------
|
|
^
/ \
/ \
/ roof \

Thanks for your advice

Tim
paul swed
2014-10-12 14:19:09 UTC
Permalink
Tim
The antennas should not interfere with each other due to rf leakage because
of the way the systems are designed. I will believe you are using 2 rf
feeds.
The more you can clear the trees the better. My very simple solution is a
90' tower.
A bit of humor it does have other uses.
Regards
Paul
WB8TSL
Post by swingbyte
Hi All,
I am building a house extension and part of the works involves adding a
new hip roof made of corrugated iron. I was thinking I would pass a 50mm
pvc pipe through the roof with a tee and then mount two conical gps timing
antennas on top of it. I am in a low point and don't have visibility of
the horizons ( I'm not in the out-back).
My question is should I mount on the peak of the roof? How close can I
mount two antennas from each other? Can they interfere with each other? I
am also in the midst of some tall trees - although my new roof will be
pretty high it will still be below the tallest trees.
Of course the main reason for this is I want to do some accurate timing
ASCII art of proposed set-up
A A
| |
--------------------
|
|
^
/ \
/ \
/ roof \
Thanks for your advice
Tim
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Bob Camp
2014-10-12 18:37:18 UTC
Permalink
Hi

If you are going to get any benefit from multiple antennas, you want to space them as far apart as possible. You are better off with one antenna and a splitter than with two close spaced antennas.

The cost of mucking around on the roof is non-trivial. The world is headed to L1/L2 operation on GPS and similar systems. Invest the money in one good antenna and mount rather than multiples.

Bob
Post by paul swed
Tim
The antennas should not interfere with each other due to rf leakage because
of the way the systems are designed. I will believe you are using 2 rf
feeds.
The more you can clear the trees the better. My very simple solution is a
90' tower.
A bit of humor it does have other uses.
Regards
Paul
WB8TSL
Post by swingbyte
Hi All,
I am building a house extension and part of the works involves adding a
new hip roof made of corrugated iron. I was thinking I would pass a 50mm
pvc pipe through the roof with a tee and then mount two conical gps timing
antennas on top of it. I am in a low point and don't have visibility of
the horizons ( I'm not in the out-back).
My question is should I mount on the peak of the roof? How close can I
mount two antennas from each other? Can they interfere with each other? I
am also in the midst of some tall trees - although my new roof will be
pretty high it will still be below the tallest trees.
Of course the main reason for this is I want to do some accurate timing
ASCII art of proposed set-up
A A
| |
--------------------
|
|
^
/ \
/ \
/ roof \
Thanks for your advice
Tim
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Chris Albertson
2014-10-12 15:17:45 UTC
Permalink
First off, why only 50mm and why plastic? The PVC will degrade in the
sunlight over the years. Use galvanized iron pipe. Make the mast as
tall as you can. It can extend sever feet below the roof and attach to
house structure using u-bolts. (Hight limited only by appearance from the
street.) Using iron pipe strength will not be an issue. Run the cable
inside the iron pipe to the attic space.

I would use two masts, one for each antenna. It will look better and be
easier to build and it will handle high winds better.

If you are worried about how this all looks use some spray paint to make it
either sky blue or light grey.

Do you need two antenna? You can feed multiple GPS receivers using a
splitter and amplifier from one antenna.

Be sure to follow the local rules for grounding antenna. In most places
you will need a heavy coper wire leading directly to a grounding rod. You
want to give lightening an easy path to ground that is not routed through
the interior of the house.
Post by swingbyte
Hi All,
I am building a house extension and part of the works involves adding a
new hip roof made of corrugated iron. I was thinking I would pass a 50mm
pvc pipe through the roof with a tee and then mount two conical gps timing
antennas on top of it. I am in a low point and don't have visibility of
the horizons ( I'm not in the out-back).
My question is should I mount on the peak of the roof? How close can I
mount two antennas from each other? Can they interfere with each other? I
am also in the midst of some tall trees - although my new roof will be
pretty high it will still be below the tallest trees.
Of course the main reason for this is I want to do some accurate timing
ASCII art of proposed set-up
A A
| |
--------------------
|
|
^
/ \
/ \
/ roof \
Thanks for your advice
Tim
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
--
Chris Albertson
Redondo Beach, California
Hal Murray
2014-10-12 21:07:53 UTC
Permalink
Post by Bob Camp
If you are going to get any benefit from multiple antennas, you want to
space them as far apart as possible. You are better off with one antenna and
a splitter than with two close spaced antennas.
Does anybody have data? How would I measure it?

Where is the knee? I assume the distance is measured in wavelengths. Is it
1, 10, ...?


In a related area, does anybody have data that correlates with rain? (or
fog/mist)
--
These are my opinions. I hate spam.
Bob Camp
2014-10-12 22:29:14 UTC
Permalink
HI

Many years ago, we got dinged on customer visit when they spotted our GPS antenna array on the roof. The claim made at the time was that anything under 20’ spacing was counterproductive. I’ve seen numbers like 5, 8, 10,15 and 25 feet mentioned by different people at different times.

The problems seem to be:

1) You have an amp in the antenna, like it or not, the antenna (and it’s coax) are not 100% shielded. They re-radiate.
2) The antenna structure (mast etc) is a reflector and you get multi-path.
3) The GPS solution does not vary enough over a short distance for a “second opinion” to be useful
4) Gear on the other end of the antenna could re-radiate. (number 4 on the list for an obvious reason … = I don’t believe it)

The first one on the list is what they dinged us on. Since it was their antenna, we sort of figured they knew something about what it did or did not do. The other three get mentioned here and there.

Bob
Post by Hal Murray
Post by Bob Camp
If you are going to get any benefit from multiple antennas, you want to
space them as far apart as possible. You are better off with one antenna and
a splitter than with two close spaced antennas.
Does anybody have data? How would I measure it?
Where is the knee? I assume the distance is measured in wavelengths. Is it
1, 10, ...?
In a related area, does anybody have data that correlates with rain? (or
fog/mist)
--
These are my opinions. I hate spam.
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Hal Murray
2014-10-16 02:56:48 UTC
Permalink
Is it silicon or is it something more exotic? In general, exotic is not good
for 1/F noise.
Data sheets say "submicron CMOS".
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Hal Murray
2014-10-20 17:15:28 UTC
Permalink
The combination of the constellation and the ionosphere are what I believe
give you the once a day (rather than once per 12 hours) bump.
There is another layer. In addition to the "normal" once-a-day type
differences, the pattern of satellites drifts slowly from day to day. So
there is another pattern with a period of something like a month. If you
have a marginal setup, for example an indoor antenna, you can see things like
the holdover times drifting both in time-of-day when they happen and in
length of holdover as the satellite pattern at dawn/dusk changes.

Of course, at that level of detail, there are lots of other contributions
like rain that will also show up and may be more important.
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Hal Murray
2014-09-07 01:13:43 UTC
Permalink
The biggest problem comes from crystal spurs rather than crystal Q.
What's the mechanism for making spurs with a crystal?
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Andrew Rodland
2014-09-07 01:42:06 UTC
Permalink
Post by Hal Murray
What's the mechanism for making spurs with a crystal?
Get the corners nice and pointy and strap it to a boot.
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Bob Camp
2014-09-07 02:20:38 UTC
Permalink
Hi

Simple answer = crystals are never perfect.

Longer winded, but very incomplete answer =

A spurious response in a crystal normally refers to a mode that is not one of the “identified” modes of the crystal. An AT has a set of identified modes, an SC has a more complex set of modes. In the case of the AT it would be the fundamental and the odd overtones. In the case of the SC you have the A, B, C modes and their odd overtones. None of those are considered spurious.

A spur can come from a lot of different places. One common one is higher order vibrations in a longer dimension face of the resonator. The 183rd overtone of the width of the blank is still a legitimate resonant mode. Another source are modes other than shear (like flex). Deriving a full catalog of all the modes of an arbitrary blank design is a major project. There are only a handful of people out there who are into that sort of thing (as opposed to simply cranking through some formulas).

Practical answer = Don’t worry about it. Unless you are building a wide pull VCXO or a wide deviation VCXO (often the same thing) you will never notice them.

Bob
Post by Hal Murray
The biggest problem comes from crystal spurs rather than crystal Q.
What's the mechanism for making spurs with a crystal?
--
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Bernd Neubig
2014-09-10 13:27:41 UTC
Permalink
Hi Bob,

your description oft he spurious coming from higher overtone of low-frequency modes is correct. I want to add, that all thickness-shear mode crystals (such as AT, BT and SC-cut) have so-called an-harmonic spurious modes, which is a whole ensemble of spurs located slightly above above the main mode (fundamental or overtone mode). "slightly means starting at about 50 kHz to 200 kHz above for fundamental mode and about 30 ... 50 kHz above for overtone modes. These an-harmonic modes are relaled to the length and width of the active area (electrode).
These spurious modes do not come only into play for wide-pull VCXO, but also in the case that the EFC input is used for modulation with signals in the audio frequency range.
Remember that a frequency modulated signal has side-lines which are N* the audio frequency apart from the carrier. The amplitude of these side lines follows the so-called Bessel functions and varies with the modulation index.
If it happens that such a "Bessel-line" for a particular modulation frequency coincides with such a spur, it comes to an interference, This means the modulation frequency response becomes a discontinuity (dip) at a sharp frequency. Such band breaks do even occur if the spurious is so weak that it can barely be seen on a network analyzer.

Regards

Bernd DK1AG
AXTAL GmbH & Co. KG
www.axtal.com

-----Ursprüngliche Nachricht-----
Von: time-nuts [mailto:time-nuts-***@febo.com] Im Auftrag von Bob Camp
Gesendet: Sonntag, 7. September 2014 04:21
An: Discussion of precise time and frequency measurement
Betreff: Re: [time-nuts] OCXO Voltage Input? (Bob Camp)

Hi

Simple answer = crystals are never perfect.

Longer winded, but very incomplete answer =

A spurious response in a crystal normally refers to a mode that is not one of the “identified” modes of the crystal. An AT has a set of identified modes, an SC has a more complex set of modes. In the case of the AT it would be the fundamental and the odd overtones. In the case of the SC you have the A, B, C modes and their odd overtones. None of those are considered spurious.

A spur can come from a lot of different places. One common one is higher order vibrations in a longer dimension face of the resonator. The 183rd overtone of the width of the blank is still a legitimate resonant mode. Another source are modes other than shear (like flex). Deriving a full catalog of all the modes of an arbitrary blank design is a major project. There are only a handful of people out there who are into that sort of thing (as opposed to simply cranking through some formulas).

Practical answer = Don’t worry about it. Unless you are building a wide pull VCXO or a wide deviation VCXO (often the same thing) you will never notice them.

Bob
Post by Hal Murray
The biggest problem comes from crystal spurs rather than crystal Q.
What's the mechanism for making spurs with a crystal?
--
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Magnus Danielson
2014-09-10 16:50:29 UTC
Permalink
Bernd,

Brilliant point. Easy to miss if one has a to simple model of the
oscillator at hand.

Since it is a single-side-band mode, it will show up both as AM and PM
with the same amplitude.

Cheers,
Magnus
Post by Bernd Neubig
Hi Bob,
your description oft he spurious coming from higher overtone of low-frequency modes is correct. I want to add, that all thickness-shear mode crystals (such as AT, BT and SC-cut) have so-called an-harmonic spurious modes, which is a whole ensemble of spurs located slightly above above the main mode (fundamental or overtone mode). "slightly means starting at about 50 kHz to 200 kHz above for fundamental mode and about 30 ... 50 kHz above for overtone modes. These an-harmonic modes are relaled to the length and width of the active area (electrode).
These spurious modes do not come only into play for wide-pull VCXO, but also in the case that the EFC input is used for modulation with signals in the audio frequency range.
Remember that a frequency modulated signal has side-lines which are N* the audio frequency apart from the carrier. The amplitude of these side lines follows the so-called Bessel functions and varies with the modulation index.
If it happens that such a "Bessel-line" for a particular modulation frequency coincides with such a spur, it comes to an interference, This means the modulation frequency response becomes a discontinuity (dip) at a sharp frequency. Such band breaks do even occur if the spurious is so weak that it can barely be seen on a network analyzer.
Regards
Bernd DK1AG
AXTAL GmbH & Co. KG
www.axtal.com
-----Ursprüngliche Nachricht-----
Gesendet: Sonntag, 7. September 2014 04:21
An: Discussion of precise time and frequency measurement
Betreff: Re: [time-nuts] OCXO Voltage Input? (Bob Camp)
Hi
Simple answer = crystals are never perfect.
Longer winded, but very incomplete answer =
A spurious response in a crystal normally refers to a mode that is not one of the “identified” modes of the crystal. An AT has a set of identified modes, an SC has a more complex set of modes. In the case of the AT it would be the fundamental and the odd overtones. In the case of the SC you have the A, B, C modes and their odd overtones. None of those are considered spurious.
A spur can come from a lot of different places. One common one is higher order vibrations in a longer dimension face of the resonator. The 183rd overtone of the width of the blank is still a legitimate resonant mode. Another source are modes other than shear (like flex). Deriving a full catalog of all the modes of an arbitrary blank design is a major project. There are only a handful of people out there who are into that sort of thing (as opposed to simply cranking through some formulas).
Practical answer = Don’t worry about it. Unless you are building a wide pull VCXO or a wide deviation VCXO (often the same thing) you will never notice them.
Bob
Post by Hal Murray
The biggest problem comes from crystal spurs rather than crystal Q.
What's the mechanism for making spurs with a crystal?
--
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Bob Camp
2014-09-10 22:18:11 UTC
Permalink
Hi

If you are modulating a normal OCXO EFC with audio, and the output frequency is not being multiplied up, the modulation index will be very low. Low modulation index means that the higher order FM sidebands will be quite far down.

If you take “audio” to be < 10 KHz, and a VHF OCXO to be 100 MHz: With a 10 ppm EFC range, you get 1.0 KHz of deviation. The modulation index is < 1 a decade below your upper modulation frequency. That’s already a pretty wide swing OCXO and a fairly high modulation frequency for an EFC line.

If you have a spur that is in the 50 to 150 KHz range, you are talking about the 5th to 15th sideband off of 10 KHz or the 50th to 150th sideband off of 1 KHz. At 50 sidebands out and an index of 1, you are in the “forget about it” region. Even at 10 KHz, the sideband is not likely to create much of an issue. The distortion from the non-linear EFC slope will be more of a problem in a practical sense.

——

Since the modulation is single sideband, yes it converts PM <-> AM. It also will be impacted by any limiters in the system and will not multiply the same way as a pure PM modulation. The phase of the sideband will change as you go through the resonance, further messing up the multiplication / limiter math.

Bob
Post by Magnus Danielson
Bernd,
Brilliant point. Easy to miss if one has a to simple model of the oscillator at hand.
Since it is a single-side-band mode, it will show up both as AM and PM with the same amplitude.
Cheers,
Magnus
Post by Bernd Neubig
Hi Bob,
your description oft he spurious coming from higher overtone of low-frequency modes is correct. I want to add, that all thickness-shear mode crystals (such as AT, BT and SC-cut) have so-called an-harmonic spurious modes, which is a whole ensemble of spurs located slightly above above the main mode (fundamental or overtone mode). "slightly means starting at about 50 kHz to 200 kHz above for fundamental mode and about 30 ... 50 kHz above for overtone modes. These an-harmonic modes are relaled to the length and width of the active area (electrode).
These spurious modes do not come only into play for wide-pull VCXO, but also in the case that the EFC input is used for modulation with signals in the audio frequency range.
Remember that a frequency modulated signal has side-lines which are N* the audio frequency apart from the carrier. The amplitude of these side lines follows the so-called Bessel functions and varies with the modulation index.
If it happens that such a "Bessel-line" for a particular modulation frequency coincides with such a spur, it comes to an interference, This means the modulation frequency response becomes a discontinuity (dip) at a sharp frequency. Such band breaks do even occur if the spurious is so weak that it can barely be seen on a network analyzer.
Regards
Bernd DK1AG
AXTAL GmbH & Co. KG
www.axtal.com
-----Ursprüngliche Nachricht-----
Gesendet: Sonntag, 7. September 2014 04:21
An: Discussion of precise time and frequency measurement
Betreff: Re: [time-nuts] OCXO Voltage Input? (Bob Camp)
Hi
Simple answer = crystals are never perfect.
Longer winded, but very incomplete answer =
A spurious response in a crystal normally refers to a mode that is not one of the “identified” modes of the crystal. An AT has a set of identified modes, an SC has a more complex set of modes. In the case of the AT it would be the fundamental and the odd overtones. In the case of the SC you have the A, B, C modes and their odd overtones. None of those are considered spurious.
A spur can come from a lot of different places. One common one is higher order vibrations in a longer dimension face of the resonator. The 183rd overtone of the width of the blank is still a legitimate resonant mode. Another source are modes other than shear (like flex). Deriving a full catalog of all the modes of an arbitrary blank design is a major project. There are only a handful of people out there who are into that sort of thing (as opposed to simply cranking through some formulas).
Practical answer = Don’t worry about it. Unless you are building a wide pull VCXO or a wide deviation VCXO (often the same thing) you will never notice them.
Bob
Post by Hal Murray
The biggest problem comes from crystal spurs rather than crystal Q.
What's the mechanism for making spurs with a crystal?
--
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Bernd Neubig
2014-09-11 08:32:40 UTC
Permalink
Hi Bob,

your example is correct. However I was not talking about OCXO specifically, but about crystal oscillators in general. And the effect I have mentioned is not limited to wide-pull VCXO, but may occur at "normal" VCXO also. I named the modulation "audio" for sake of simplicity of expression - it was certainly not accurate enough. If you are modulating data (FSK) then such interferences have a risk to occur even at moderate data rates.
I do not talk about theorectical "can be's" but about practical experience.

Best regards

Bernd


-----Ursprüngliche Nachricht-----
Von: time-nuts [mailto:time-nuts-***@febo.com] Im Auftrag von Bob Camp
Gesendet: Donnerstag, 11. September 2014 00:18
An: Discussion of precise time and frequency measurement
Betreff: Re: [time-nuts] OCXO Voltage Input? (Bob Camp)

Hi

If you are modulating a normal OCXO EFC with audio, and the output frequency is not being multiplied up, the modulation index will be very low. Low modulation index means that the higher order FM sidebands will be quite far down.

If you take “audio” to be < 10 KHz, and a VHF OCXO to be 100 MHz: With a 10 ppm EFC range, you get 1.0 KHz of deviation. The modulation index is < 1 a decade below your upper modulation frequency. That’s already a pretty wide swing OCXO and a fairly high modulation frequency for an EFC line.

If you have a spur that is in the 50 to 150 KHz range, you are talking about the 5th to 15th sideband off of 10 KHz or the 50th to 150th sideband off of 1 KHz. At 50 sidebands out and an index of 1, you are in the “forget about it” region. Even at 10 KHz, the sideband is not likely to create much of an issue. The distortion from the non-linear EFC slope will be more of a problem in a practical sense.

——

Since the modulation is single sideband, yes it converts PM <-> AM. It also will be impacted by any limiters in the system and will not multiply the same way as a pure PM modulation. The phase of the sideband will change as you go through the resonance, further messing up the multiplication / limiter math.

Bob
Post by Magnus Danielson
Bernd,
Brilliant point. Easy to miss if one has a to simple model of the oscillator at hand.
Since it is a single-side-band mode, it will show up both as AM and PM with the same amplitude.
Cheers,
Magnus
Post by Bernd Neubig
Hi Bob,
your description oft he spurious coming from higher overtone of low-frequency modes is correct. I want to add, that all thickness-shear mode crystals (such as AT, BT and SC-cut) have so-called an-harmonic spurious modes, which is a whole ensemble of spurs located slightly above above the main mode (fundamental or overtone mode). "slightly means starting at about 50 kHz to 200 kHz above for fundamental mode and about 30 ... 50 kHz above for overtone modes. These an-harmonic modes are relaled to the length and width of the active area (electrode).
These spurious modes do not come only into play for wide-pull VCXO, but also in the case that the EFC input is used for modulation with signals in the audio frequency range.
Remember that a frequency modulated signal has side-lines which are N* the audio frequency apart from the carrier. The amplitude of these side lines follows the so-called Bessel functions and varies with the modulation index.
If it happens that such a "Bessel-line" for a particular modulation frequency coincides with such a spur, it comes to an interference, This means the modulation frequency response becomes a discontinuity (dip) at a sharp frequency. Such band breaks do even occur if the spurious is so weak that it can barely be seen on a network analyzer.
Regards
Bernd DK1AG
AXTAL GmbH & Co. KG
www.axtal.com
-----Ursprüngliche Nachricht-----
Gesendet: Sonntag, 7. September 2014 04:21
An: Discussion of precise time and frequency measurement
Betreff: Re: [time-nuts] OCXO Voltage Input? (Bob Camp)
Hi
Simple answer = crystals are never perfect.
Longer winded, but very incomplete answer =
A spurious response in a crystal normally refers to a mode that is not one of the “identified” modes of the crystal. An AT has a set of identified modes, an SC has a more complex set of modes. In the case of the AT it would be the fundamental and the odd overtones. In the case of the SC you have the A, B, C modes and their odd overtones. None of those are considered spurious.
A spur can come from a lot of different places. One common one is higher order vibrations in a longer dimension face of the resonator. The 183rd overtone of the width of the blank is still a legitimate resonant mode. Another source are modes other than shear (like flex). Deriving a full catalog of all the modes of an arbitrary blank design is a major project. There are only a handful of people out there who are into that sort of thing (as opposed to simply cranking through some formulas).
Practical answer = Don’t worry about it. Unless you are building a wide pull VCXO or a wide deviation VCXO (often the same thing) you will never notice them.
Bob
Post by Hal Murray
The biggest problem comes from crystal spurs rather than crystal Q.
What's the mechanism for making spurs with a crystal?
--
These are my opinions. I hate spam.
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Bob Camp
2014-09-11 11:12:03 UTC
Permalink
Hi

I understand that we are talking about a couple of different things. Since we started out talking about OCXO’s I figured it was worth it to bring it back to where we started.

Bob
Post by Bernd Neubig
Hi Bob,
your example is correct. However I was not talking about OCXO specifically, but about crystal oscillators in general. And the effect I have mentioned is not limited to wide-pull VCXO, but may occur at "normal" VCXO also. I named the modulation "audio" for sake of simplicity of expression - it was certainly not accurate enough. If you are modulating data (FSK) then such interferences have a risk to occur even at moderate data rates.
I do not talk about theorectical "can be's" but about practical experience.
Best regards
Bernd
-----Ursprüngliche Nachricht-----
Gesendet: Donnerstag, 11. September 2014 00:18
An: Discussion of precise time and frequency measurement
Betreff: Re: [time-nuts] OCXO Voltage Input? (Bob Camp)
Hi
If you are modulating a normal OCXO EFC with audio, and the output frequency is not being multiplied up, the modulation index will be very low. Low modulation index means that the higher order FM sidebands will be quite far down.
If you take “audio” to be < 10 KHz, and a VHF OCXO to be 100 MHz: With a 10 ppm EFC range, you get 1.0 KHz of deviation. The modulation index is < 1 a decade below your upper modulation frequency. That’s already a pretty wide swing OCXO and a fairly high modulation frequency for an EFC line.
If you have a spur that is in the 50 to 150 KHz range, you are talking about the 5th to 15th sideband off of 10 KHz or the 50th to 150th sideband off of 1 KHz. At 50 sidebands out and an index of 1, you are in the “forget about it” region. Even at 10 KHz, the sideband is not likely to create much of an issue. The distortion from the non-linear EFC slope will be more of a problem in a practical sense.
——
Since the modulation is single sideband, yes it converts PM <-> AM. It also will be impacted by any limiters in the system and will not multiply the same way as a pure PM modulation. The phase of the sideband will change as you go through the resonance, further messing up the multiplication / limiter math.
Bob
Post by Magnus Danielson
Bernd,
Brilliant point. Easy to miss if one has a to simple model of the oscillator at hand.
Since it is a single-side-band mode, it will show up both as AM and PM with the same amplitude.
Cheers,
Magnus
Post by Bernd Neubig
Hi Bob,
your description oft he spurious coming from higher overtone of low-frequency modes is correct. I want to add, that all thickness-shear mode crystals (such as AT, BT and SC-cut) have so-called an-harmonic spurious modes, which is a whole ensemble of spurs located slightly above above the main mode (fundamental or overtone mode). "slightly means starting at about 50 kHz to 200 kHz above for fundamental mode and about 30 ... 50 kHz above for overtone modes. These an-harmonic modes are relaled to the length and width of the active area (electrode).
These spurious modes do not come only into play for wide-pull VCXO, but also in the case that the EFC input is used for modulation with signals in the audio frequency range.
Remember that a frequency modulated signal has side-lines which are N* the audio frequency apart from the carrier. The amplitude of these side lines follows the so-called Bessel functions and varies with the modulation index.
If it happens that such a "Bessel-line" for a particular modulation frequency coincides with such a spur, it comes to an interference, This means the modulation frequency response becomes a discontinuity (dip) at a sharp frequency. Such band breaks do even occur if the spurious is so weak that it can barely be seen on a network analyzer.
Regards
Bernd DK1AG
AXTAL GmbH & Co. KG
www.axtal.com
-----Ursprüngliche Nachricht-----
Gesendet: Sonntag, 7. September 2014 04:21
An: Discussion of precise time and frequency measurement
Betreff: Re: [time-nuts] OCXO Voltage Input? (Bob Camp)
Hi
Simple answer = crystals are never perfect.
Longer winded, but very incomplete answer =
A spurious response in a crystal normally refers to a mode that is not one of the “identified” modes of the crystal. An AT has a set of identified modes, an SC has a more complex set of modes. In the case of the AT it would be the fundamental and the odd overtones. In the case of the SC you have the A, B, C modes and their odd overtones. None of those are considered spurious.
A spur can come from a lot of different places. One common one is higher order vibrations in a longer dimension face of the resonator. The 183rd overtone of the width of the blank is still a legitimate resonant mode. Another source are modes other than shear (like flex). Deriving a full catalog of all the modes of an arbitrary blank design is a major project. There are only a handful of people out there who are into that sort of thing (as opposed to simply cranking through some formulas).
Practical answer = Don’t worry about it. Unless you are building a wide pull VCXO or a wide deviation VCXO (often the same thing) you will never notice them.
Bob
Post by Hal Murray
The biggest problem comes from crystal spurs rather than crystal Q.
What's the mechanism for making spurs with a crystal?
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Hal Murray
2014-10-30 05:31:43 UTC
Permalink
It is not at all unusual for signals to be re-clocked when going into a
micro. Often the documentation on this process is somewhere between vague
and non-exsistant.
Reclocking is almost required if you want to avoid metastability issues.

There is often some "documentation" in the form of min high/low times.
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Hal Murray
2014-11-02 21:59:06 UTC
Permalink
The numbers quoted earlier (and they sound right) were 20 uA at 2.5V. That
would be well under your 100uA. My *guess* is that self discharge / aging on
a normal AA is going to limit things faster than a 20 uA drain.
20 uA would last 15 years. (assuming no self-discharge)

Self discharge is temperature dependent. Graph here:
http://data.energizer.com/PDFs/alkaline_appman.pdf
(poke the shelf-life button on the left)

At 20C, alkaline lose 20% in 10 years. Or roughly 50 years for the whole
thing. (assuming linear and waving my hands)
The UT+ data sheet from 1998 quotes an external backup supply of 2.5 to
5.35V with a drain of 5uA typical at 2.5 Volts.
Ahhh. That would be 60 years. (assuming no self-discharge) So it's roughly
matching the self discharge rate.
Your pair of AA’s will start off at 3.1V, but they will get to 2.5 long
before they are truly dead. Is the RAM gone at 2.5000 or 2.4 or “about 2
volts” 
.
The usual cutoff is 0.8 V. It falls off quickly at the end. It's still 50%
at 1.25 V. There is a graph at the above URL.
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Mark Sims
2014-11-02 22:11:37 UTC
Permalink
If you are going to back up the clock with AA cells, use lithium primary AA cells. They will last longer, plus they don't leak. EVERY alkaline cell will eventually leak... they don't call 'em Alkaleaks for nuthin'
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Hal Murray
2014-11-09 23:07:06 UTC
Permalink
What is going on is that people are confusing the estimation process that is
used by the selection process (which does look at a lot of stuff) and how
that is described. ...
In this context, it's important to remember that there are 2 parameters
associated with the goodness of clocks. The first is the error. The second
is the error bars. For NTP, the error bars are often huge and often differ
wildly between clocks.

I don't know how that translates into getting the best out of a batch of Rbs.

NTP has another trick worth adding to the collection. For things like PPS
processing, it collects a batch of samples, then discards roughly 1/3 of them
as outliers. That helps keep an occasional bad sample from biasing the
result.
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Hal Murray
2014-11-25 05:37:06 UTC
Permalink
Maybe Tom needs a Microsoft Windows Update on his GPSDO firmware :) For some
reason the very thought of Microsoft getting involved in something like that
makes me shudder

For good reason. A friend's scope picked up a virus.
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Mark Sims
2014-11-25 07:30:35 UTC
Permalink
I once bought an HP16700 series logic analyzer off of Ebay that had a directory filled with porn on it... but that is a Unix machine.
----------------
for good reason. A friend's scope picked up a virus.
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Hal Murray
2014-11-28 23:42:41 UTC
Permalink
The “new chip ID, new com port” thing is pretty typical for the FTDI
drivers. If you plug the old LTE back in there’s a good chance it will come
back up as COMM 5. Usually they are pretty good about only adding ports for
devices they have not seen before.
Most/some of the FTDI usb to serial chips have a serial number. I don't know
how it works on Windows, but on Linux, you can use the udev rules to make an
alias so your software can refer to something with a filename like /dev/LITE
rather than /dev/ttyUSB2. It works no matter which slot you plug it into
and/or still works after it gets unplugged and reconnected.

lsusb -v will show things like:
idVendor 0x0403 Future Technology Devices International, Ltd
idProduct 0x6001 FT232 USB-Serial (UART) IC
bcdDevice 6.00
iManufacturer 1 FTDI
iProduct 2 FT232R USB UART
iSerial 3 A102GX1N

/var/log/messages or /var/log/syslog will contain something like:
Nov 28 15:12:00 deb kernel: [1392082.791230] usb 3-3: Product: FT232R USB UART
Nov 28 15:12:00 deb kernel: [1392082.791235] usb 3-3: Manufacturer: FTDI
Nov 28 15:12:00 deb kernel: [1392082.791240] usb 3-3: SerialNumber: A102GX1N
Nov 28 15:12:00 deb kernel: [1392082.799337] ftdi_sio 3-3:1.0: FTDI USB
Serial Device converter detected
Nov 28 15:12:00 deb kernel: [1392082.799447] usb 3-3: Detected FT232RL
...
Nov 28 15:12:00 deb kernel: [1392082.805436] usb 3-3: FTDI USB Serial Device
converter now attached to ttyUSB3


This is what I put in /etc/udev/rules.d/35-hgm.rules

# LTE LITE Eval Board
KERNEL=="ttyUSB*", ATTRS{serial}=="A102GX1N", MODE="0666", SYMLINK+="LITE"


I use the same approach with my Rigol scope and Prologic USB-GPIB.
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davidh
2014-11-29 03:46:33 UTC
Permalink
Hi,

For Windows, ComPortMan does a great job of managing comm port
assignments. Available at <http://www.uwe-sieber.de/comportman_e.html>

Cheers,

david
Post by Hal Murray
The “new chip ID, new com port” thing is pretty typical for the FTDI
drivers. If you plug the old LTE back in there’s a good chance it will come
back up as COMM 5. Usually they are pretty good about only adding ports for
devices they have not seen before.
Most/some of the FTDI usb to serial chips have a serial number. I don't know
how it works on Windows, but on Linux, you can use the udev rules to make an
alias so your software can refer to something with a filename like /dev/LITE
rather than /dev/ttyUSB2. It works no matter which slot you plug it into
and/or still works after it gets unplugged and reconnected.
idVendor 0x0403 Future Technology Devices International, Ltd
idProduct 0x6001 FT232 USB-Serial (UART) IC
bcdDevice 6.00
iManufacturer 1 FTDI
iProduct 2 FT232R USB UART
iSerial 3 A102GX1N
Nov 28 15:12:00 deb kernel: [1392082.791230] usb 3-3: Product: FT232R USB UART
Nov 28 15:12:00 deb kernel: [1392082.791235] usb 3-3: Manufacturer: FTDI
Nov 28 15:12:00 deb kernel: [1392082.791240] usb 3-3: SerialNumber: A102GX1N
Nov 28 15:12:00 deb kernel: [1392082.799337] ftdi_sio 3-3:1.0: FTDI USB
Serial Device converter detected
Nov 28 15:12:00 deb kernel: [1392082.799447] usb 3-3: Detected FT232RL
....
Nov 28 15:12:00 deb kernel: [1392082.805436] usb 3-3: FTDI USB Serial Device
converter now attached to ttyUSB3
This is what I put in /etc/udev/rules.d/35-hgm.rules
# LTE LITE Eval Board
KERNEL=="ttyUSB*", ATTRS{serial}=="A102GX1N", MODE="0666", SYMLINK+="LITE"
I use the same approach with my Rigol scope and Prologic USB-GPIB.
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Orin Eman
2014-11-29 05:41:57 UTC
Permalink
Post by Hal Murray
The “new chip ID, new com port” thing is pretty typical for the FTDI
drivers. If you plug the old LTE back in there’s a good chance it will
come
back up as COMM 5. Usually they are pretty good about only adding ports
for
devices they have not seen before.
Most/some of the FTDI usb to serial chips have a serial number. I don't know
how it works on Windows, but on Linux, you can use the udev rules to make an
alias so your software can refer to something with a filename like /dev/LITE
rather than /dev/ttyUSB2. It works no matter which slot you plug it into
and/or still works after it gets unplugged and reconnected.
It's really a limitation of USB. You have the vendor ID, product ID, and
for some devices, a serial number.

IF the device has a serial number, next time it's plugged in, the OS can be
pretty certain it's the same device and can use the same COM port or device
assignment as last time. If not, all bets are off.

If a USB device has no serial number, Windows choses to use the physical
USB port the device is plugged into. I.e. if you plug such a device with
the same vendor ID/product ID into the same USB port, you get the same COM
port assignment. I really don't know of a better way. It's unfortunate
that for a device with no serial number, if you plug the same device into a
different USB port, you get a different COM port, but it is the best
solution for the case where you have more than one USB device with the same
vendor ID/product ID... it works just the same as traditional RS232 ports:
the COM port assignment depends on which socket you plug the device in.

It is also unfortunate that the USB specs allowed this to happen and didn't
require devices to have a serial number.
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Bob Stewart
2014-11-29 06:04:54 UTC
Permalink
For Linux, I worked this up and posted to linuxquestions.org.  I don't guarantee it, but it's been working for the PL-2303 devices for me.  It just creates a link to the "real" driver.  There are probably better ways to do it.

File: /etc/udev/rules.d/70-persistent-usb.rulesACTION=="add", KERNEL=="ttyUSB[0-9]*", PROGRAM="/etc/udev/rules.d/usb-parse-devpath.pm %p", SYMLINK+="ttyUSB%c"
File: /etc/udev/rules.d/usb-parse-devpath.pm#!/usr/bin/perl -w

@items = split("/", $ARGV[0]);
for ($i = 0; $i < @items; $i++) {
if ($items[$i] =~ m/^usb[0-9]+$/) {

if ($items[$i + 2] =~ m/:/) {
print $items[$i + 1] . "\n";
} else {
print $items[$i + 2] . "\n";
}

last;
}
}

Example:
crw-rw---- 1 root dialout 188, 0 Nov 28 20:59 /dev/ttyUSB0
crw-rw---- 1 root dialout 188, 1 Nov 28 23:43 /dev/ttyUSB1
lrwxrwxrwx 1 root root         7 Nov 17 23:39 /dev/ttyUSB1-2 -> ttyUSB0
lrwxrwxrwx 1 root root         7 Nov 22 21:17 /dev/ttyUSB4-2 -> ttyUSB1
If the two code boxes don't make it through the list forwarder, the code can be found here.  Read the whole thread as I didn't put it all in the final post:
www.linuxquestions.org/questions/linux-hardware-18/usb-pl2303-reliable-device-names-4175506134/

Bob
From: Orin Eman <***@gmail.com>
To: Discussion of precise time and frequency measurement <time-***@febo.com>
Sent: Friday, November 28, 2014 11:41 PM
Subject: Re: [time-nuts] LTE-Lite
The “new chip ID, new com port” thing is pretty typical for the FTDI
drivers. If you plug the old LTE back in there’s a good chance it will
come
back up as COMM 5. Usually they are pretty good about only adding ports
for
devices they have not seen before.
Most/some of the FTDI usb to serial chips have a serial number.  I don't
know
how it works on Windows, but on Linux, you can use the udev rules to make an
alias so your software can refer to something with a filename like /dev/LITE
rather than /dev/ttyUSB2.  It works no matter which slot you plug it into
and/or still works after it gets unplugged and reconnected.
It's really a limitation of USB.  You have the vendor ID, product ID, and
for some devices, a serial number.

IF the device has a serial number, next time it's plugged in, the OS can be
pretty certain it's the same device and can use the same COM port or device
assignment as last time.  If not, all bets are off.

If a USB device has no serial number, Windows choses to use the physical
USB port the device is plugged into.  I.e. if you plug such a device with
the same vendor ID/product ID into the same USB port, you get the same COM
port assignment.  I really don't know of a better way.  It's unfortunate
that for a device with no serial number, if you plug the same device into a
different USB port, you get a different COM port, but it is the best
solution for the case where you have more than one USB device with the same
vendor ID/product ID... it works just the same as traditional RS232 ports:
the COM port assignment depends on which socket you plug the device in.

It is also unfortunate that the USB specs allowed this to happen and didn't
require devices to have a serial number.


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Hal Murray
2014-12-02 03:29:50 UTC
Permalink
4 RX+
8 RX-
Looks good.
5 TX+
6 TX-
I think there is a typo in there. That should be pins 5 and 9.
I'm using pins 9, 8, and 7 as per Stewart's message that started this
discussion.
3 and 7 ground
Pins 1, 2, and 6 seem not-connected. (That's using a scope without a ground
clip. I see slight fuzz on pins 3 and 7, nothing on 1, 2 and 6.)

The above is on J8, Diagnoistic.

--------

J6, RS422/PPS has the same (5, 9) TX pins. If you shift the cable over there
it gets a line each second. This can be handy for checking that direction of
your setup.

Pins 1 and 6 are the PPS pulse. 400 microseconds wide. It's not active on
my box that's in STBY.

Pins 4 and 8 look like inputs. Does anybody know what you can send in there?
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Götz Romahn
2014-12-02 09:50:17 UTC
Permalink
Am 02.12.2014 04:29, :
Hal, (see below)
Post by Hal Murray
4 RX+
8 RX-
Looks good.
5 TX+
6 TX-
I think there is a typo in there. That should be pins 5 and 9.
I'm using pins 9, 8, and 7 as per Stewart's message that started this
discussion.
3 and 7 ground
Pins 1, 2, and 6 seem not-connected. (That's using a scope without a ground
clip. I see slight fuzz on pins 3 and 7, nothing on 1, 2 and 6.)
The above is on J8, Diagnoistic.
--------
J6, RS422/PPS has the same (5, 9) TX pins. If you shift the cable over there
it gets a line each second. This can be handy for checking that direction of
your setup.
Pins 1 and 6 are the PPS pulse. 400 microseconds wide. It's not active on
my box that's in STBY.
Pins 4 and 8 look like inputs. Does anybody know what you can send in there?Hal,
it's already known to us:

http://www.mail-archive.com/time-nuts%40febo.com/msg69593.html

Götz
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Hal Murray
2014-12-06 02:36:00 UTC
Permalink
Running one locked to each system is really the only approach that makes
sense. There inevitably are minor differences in systems and trying to
average things out is not the best way to do it.
Anybody have suggestions for a low cost receiver to run that test?
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Bob Camp
2014-12-06 03:14:53 UTC
Permalink
Post by Hal Murray
Running one locked to each system is really the only approach that makes
sense. There inevitably are minor differences in systems and trying to
average things out is not the best way to do it.
Anybody have suggestions for a low cost receiver to run that test?
Low cost … hmmm …. The stuff we normally buy is surplus / used. That makes it the 10 cents or 1 cent on the dollar that we’re used to paying. This stuff (by definition) is brand new and fresh on the market.


LTE-Lite will do QZSS .. might not have sat’s overhead in your location :)

Google suggests:

Meinberg has the GLN180PEX that will do Glonass timing

Teseo-3 / Teseo-2 do various constellations

uBlox 6 claims GPS / Glonass / QZSS

http://www.u-blox.com/images/downloads/Product_Docs/u-blox6-GPS-GLONASS-QZSS-V14_ReceiverDescriptionProtocolSpec_Public_(GPS.G6-SW-12013).pdf

A bunch of Garmin stuff will do Glonass

https://support.garmin.com/support/searchSupport/case.faces?caseId=%7Ba3bcf150-1fa1-11e1-73d0-000000000000%7D

Furuno GT-87 has Glonass and QZSS

NovAtel OEM6 has Glonass, Galileo, and BeiDou








Bob
Post by Hal Murray
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Hal Murray
2014-12-06 11:36:04 UTC
Permalink
From a few days ago...
Post by Götz Romahn
Post by Hal Murray
Pins 4 and 8 look like inputs. Does anybody know what you
can send in there?
http://www.mail-archive.com/time-nuts%40febo.com/msg69593.html
Thanks.

Summary:
If you send "ptim:tcod:cont 0", that turns off the automatic (continuous)
time messages.
It doesn't turn on sending "scpi > " to tell you when it is ready for
another command.

Without the scpi, I thought a short delay might be needed. Except for two
cases, it isn't. There may be more cases that I haven't discovered.

The first case is switching to T2 mode. It takes about a second for the scpi
on the Diagnostic port. I assume it's writing to flash. A delay in that
path works without any delay in the normal case.

The other case that needs special handling is the status page. I check for
"Self Test:", then in the normal case discard the scpi.

I have python code that does what I want and works on both J6 (no scpi) and
J8 (with scpi). Every 30 seconds, it reads several parameters and writes
them to a log file, then displays the status page. Poke me off-list if you
want a copy. It's running on Linux but might be easy to port to Windows.

The bottom line is that you (or NTP) can get both the text interface and PPS
on a single connector.
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Hal Murray
2014-12-12 02:32:59 UTC
Permalink
I would bet the power supply is some sort of “brick”. That could make it a
bit tough to replace.
Power supply bricks were quite popular 10 years ago. There were several
companies making them. Sizes and pinouts were reasonably standard. I
haven't looked recently. It might not be all that hard to find a replacement.

On the other hand, the ones in a GPSDO might be special - more power in the
+12 supply to drive the oven.
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Hal Murray
2014-12-14 21:21:45 UTC
Permalink
My guess is that there is no PPS out of the device. It would be very unusual
if there was. Finding the NEMA output pin should be possible with an
oscilloscope. At that point, a simple serial connection to the server is
about all you need. Bring up the NEMA driver and it is running.
You may need an inverter in the serial path.

I'd expect there to be a PPS signal coming out of a GPS module. It is often
left unconnected, or connected to a LED.
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Hal Murray
2014-12-16 01:07:07 UTC
Permalink
The problem shows up when the GPS constellation is in a configuration that
accentuates the error. That’s often a 12 / 24 / 48 hour sort of thing.
It would be interesting to compare the results from daytime vs nighttime, or
today vs yesterday.
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Bob Camp
2014-12-16 01:18:34 UTC
Permalink
Hi
Post by Hal Murray
The problem shows up when the GPS constellation is in a configuration that
accentuates the error. That’s often a 12 / 24 / 48 hour sort of thing.
It would be interesting to compare the results from daytime vs nighttime, or
today vs yesterday.
There can be seasonal issues (trees sprout leaves …) as well.

Bob
Post by Hal Murray
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Hal Murray
2015-04-08 07:45:47 UTC
Permalink
Now you need to sort out the B, the A+ and the B+ in the Raspberry world.
There may be more that I have not yet noticed. As far as I can tell, they
all are pretty limited once you get past the tight video integration on the
B and B+.
There is also the 2B with 1 GB and a 4 core CPU.

The A, A+, B, and B+ have a 700 MHz CPU.
The 2B has a quad core 900 MHz CPU.

The A and A+ don't have an Ethernet.
The A+ has a smaller card size.

The A and A+ have 1 USB port.
The B has 2 USB ports.
The B+ and 2B have 4 USB ports.

The A and A+ have 256 MB.
The B and B+ have 512 MB.
The 2B has 1 GB.

The B+ and 2B have the same connector layout. (they use the same case)

http://en.wikipedia.org/wiki/Raspberry_Pi
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Hal Murray
2015-05-19 08:14:12 UTC
Permalink
The complexity is not in the data translation, it’s in the timing of the
whole thing. The firmware in the TS2100 was designed and tested with a
particular order of sentences and timing between them and the pps output of
the Trimble ACE. Upset that timing (by delaying the data) and you may up
upset the firmware’s expectations about when the data ...
It would probably take some experimentation to figure out what fields the
TS2100 actually uses.

Assuming you know what it needs, my expectation is that the serial data
stream would be delayed by one character time. Mostly, it's just read a
character from the input UART and copy it to the output UART. Then you have
to watch the data stream and find the sentences you want to modify. If it's
just the week number, that's as simple as add 0x?? to byte ?? of sentence
type ??. If the date used by the TS2100 is in year/month/day format, then
it's replace several bytes with the precomputed correct data. There is most
of a second to do that computation.

If there is a checksum, that will have to be corrected on the fly. That
shouldn't be hard.

-----

Things get interesting if the local clock used by the output UART is slightly
slower than the clock used to send to your input UART.

The output is probably double buffered. That extra character will support
some clock skew. The critical factor is how long the data stream is between
pauses. If the worst case clock difference is 200 ppm (100 ppm each), it
takes a 5000 character burst to overrun a 1 (extra) character buffer. 9600
baud is 1000 characters per second so that's a 5 second burst.

(Ethernet hubs/repeaters have the same problem. They have to buffer up
enough data before starting to transmit so that the buffer doesn't run dry if
the clocks are off in one direction and the buffer has to be big enough to
hold the extra if the clocks are off in the other direction. Both scale with
the max packet length.)

Another approach would be to hack the transmit baud rate to be slightly fast,
say 9602 so it won't be slower at the worst case clock speed difference.
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Lizeth Norman
2015-05-19 13:32:37 UTC
Permalink
I've got an NO 24 that I bought for a ts-2100 that died on the table.

Anyone interested in a trade or ??
Norm n3ykf
Post by Hal Murray
The complexity is not in the data translation, it’s in the timing of the
whole thing. The firmware in the TS2100 was designed and tested with a
particular order of sentences and timing between them and the pps output of
the Trimble ACE. Upset that timing (by delaying the data) and you may up
upset the firmware’s expectations about when the data ...
It would probably take some experimentation to figure out what fields the
TS2100 actually uses.
Assuming you know what it needs, my expectation is that the serial data
stream would be delayed by one character time. Mostly, it's just read a
character from the input UART and copy it to the output UART. Then you have
to watch the data stream and find the sentences you want to modify. If it's
just the week number, that's as simple as add 0x?? to byte ?? of sentence
type ??. If the date used by the TS2100 is in year/month/day format, then
it's replace several bytes with the precomputed correct data. There is most
of a second to do that computation.
If there is a checksum, that will have to be corrected on the fly. That
shouldn't be hard.
-----
Things get interesting if the local clock used by the output UART is slightly
slower than the clock used to send to your input UART.
The output is probably double buffered. That extra character will support
some clock skew. The critical factor is how long the data stream is between
pauses. If the worst case clock difference is 200 ppm (100 ppm each), it
takes a 5000 character burst to overrun a 1 (extra) character buffer. 9600
baud is 1000 characters per second so that's a 5 second burst.
(Ethernet hubs/repeaters have the same problem. They have to buffer up
enough data before starting to transmit so that the buffer doesn't run dry if
the clocks are off in one direction and the buffer has to be big enough to
hold the extra if the clocks are off in the other direction. Both scale with
the max packet length.)
Another approach would be to hack the transmit baud rate to be slightly fast,
say 9602 so it won't be slower at the worst case clock speed difference.
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Bob Camp
2015-05-19 21:38:48 UTC
Permalink
HI

I’d bet that the ACE is supplying full time / date info to the TS2100. That’s what
every module I’ve seen does. No reason to play with the GPS weeks if you don’t
have to. Use the date from the receiver.

Assuming that’s correct. You have a lot more to do than flip one bit in at one point
in one string. Also remember - you need to delay all of the week / hour / minute switch
points by the number of leap seconds that the ACE does not know about.

Bob
Post by Hal Murray
The complexity is not in the data translation, it’s in the timing of the
whole thing. The firmware in the TS2100 was designed and tested with a
particular order of sentences and timing between them and the pps output of
the Trimble ACE. Upset that timing (by delaying the data) and you may up
upset the firmware’s expectations about when the data ...
It would probably take some experimentation to figure out what fields the
TS2100 actually uses.
Assuming you know what it needs, my expectation is that the serial data
stream would be delayed by one character time. Mostly, it's just read a
character from the input UART and copy it to the output UART. Then you have
to watch the data stream and find the sentences you want to modify. If it's
just the week number, that's as simple as add 0x?? to byte ?? of sentence
type ??. If the date used by the TS2100 is in year/month/day format, then
it's replace several bytes with the precomputed correct data. There is most
of a second to do that computation.
If there is a checksum, that will have to be corrected on the fly. That
shouldn't be hard.
-----
Things get interesting if the local clock used by the output UART is slightly
slower than the clock used to send to your input UART.
The output is probably double buffered. That extra character will support
some clock skew. The critical factor is how long the data stream is between
pauses. If the worst case clock difference is 200 ppm (100 ppm each), it
takes a 5000 character burst to overrun a 1 (extra) character buffer. 9600
baud is 1000 characters per second so that's a 5 second burst.
(Ethernet hubs/repeaters have the same problem. They have to buffer up
enough data before starting to transmit so that the buffer doesn't run dry if
the clocks are off in one direction and the buffer has to be big enough to
hold the extra if the clocks are off in the other direction. Both scale with
the max packet length.)
Another approach would be to hack the transmit baud rate to be slightly fast,
say 9602 so it won't be slower at the worst case clock speed difference.
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Hal Murray
2015-06-11 01:50:11 UTC
Permalink
2) Check the output levels from the Z3801 with a scope. ...
A quick power cycle between each of the 9 possibilities should get it
feeding out something that you can recognize. Yes this is a generic
approach, but sometimes the generic one is quicker than doing a bunch of
research, looking for notes on how you switched the thing around back months
ago 
.
If you have the scope out, you can easily check the baud rate and with a bit
more work you can probably get the parity.
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Hal Murray
2015-06-13 23:30:02 UTC
Permalink
The very real question is still - which edge is correct?
Has anybody seen a GPSDO where the leading edge of a narrow pulse wasn't the
correct one?
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Bob Camp
2015-06-14 13:30:27 UTC
Permalink
Hi

Not just positive and negative, is the even second output closer than the pps output. Since
you have dug a signal out of the guts of the thing, you need to qualify what it actually is.

Bob
Post by Hal Murray
The very real question is still - which edge is correct?
Has anybody seen a GPSDO where the leading edge of a narrow pulse wasn't the
correct one?
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Hal Murray
2015-06-16 03:26:09 UTC
Permalink
Since the internal PLL’s have jitter in the 20 to 30 ps RMS range, that
limits a lot of the data you get.
I haven't looked recently, but I doubt if much has changed. Xilinx uses DLLs
rather than PLLs.

They have a long chain of buffers and a giant multiplexor to select the right
tap.

Does anybody have data on what the "jitter" actually looks like? I'd expect
several blurry peaks, with the spacing between peaks being the step size of
the delay/mux chain and the blur being wider if there is more random logic.
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Bob Camp
2015-06-16 11:06:45 UTC
Permalink
Hi
Post by Hal Murray
Since the internal PLL’s have jitter in the 20 to 30 ps RMS range, that
limits a lot of the data you get.
I haven't looked recently, but I doubt if much has changed. Xilinx uses DLLs
rather than PLLs.
The jitter on both clock sources looks pretty gaussian.
Post by Hal Murray
They have a long chain of buffers and a giant multiplexor to select the right
tap.
Does anybody have data on what the "jitter" actually looks like? I'd expect
several blurry peaks, with the spacing between peaks being the step size of
the delay/mux chain and the blur being wider if there is more random logic.
The calibration output is a mess …

Bob
Post by Hal Murray
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Hal Murray
2015-07-01 03:38:19 UTC
Permalink
Any observations of anomalous behavior yet?
From a BU-353:
57203 86380.750 $GPRMC,235940.000,A,3726.0893,N,12212.2627,W,0.52,64.49,300615
,,*20
57203 86381.748 $GPRMC,235941.000,A,3726.0889,N,12212.2627,W,0.45,78.54,300615
,,*2D
57203 86383.138 $GPRMC,235942.000,A,3726.0883,N,12212.2627,W,0.82,157.71,30061
5,,*14
57203 86383.752 $GPRMC,235943.000,A,3726.0874,N,12212.2628,W,1.71,186.96,30061
5,,*1A
57203 86384.750 $GPRMC,235944.000,A,3726.0866,N,12212.2630,W,1.33,180.14,30061
5,,*1D
57203 86385.752 $GPRMC,235944.000,A,3726.0858,N,12212.2631,W,1.10,178.01,30061
5,,*13
57203 86386.751 $GPRMC,235945.000,A,3726.0850,N,12212.2632,W,1.18,179.98,30061
5,,*10
57203 86388.136 $GPRMC,235946.000,A,3726.0842,N,12212.2630,W,1.67,146.83,30061
5,,*1C
57203 86388.752 $GPRMC,235947.000,A,3726.0836,N,12212.2627,W,1.15,129.24,30061
5,,*19

From a MR-350P
57203 86382.186 $GPRMC,235941.000,A,3726.0808,N,12212.2649,W,0.27,67.38,300615
,,*2C
57203 86382.799 $GPRMC,235942.000,A,3726.0807,N,12212.2652,W,0.37,210.08,30061
5,,*1A
57203 86383.805 $GPRMC,235943.000,A,3726.0811,N,12212.2647,W,0.48,95.98,300615
,,*26
57203 86384.807 $GPRMC,235944.000,A,3726.0812,N,12212.2647,W,0.17,210.63,30061
5,,*13
57203 86385.806 $GPRMC,235944.000,A,3726.0810,N,12212.2648,W,0.29,145.10,30061
5,,*14
57203 86387.188 $GPRMC,235945.000,A,3726.0809,N,12212.2647,W,0.39,174.68,30061
5,,*1E
57203 86387.807 $GPRMC,235946.000,A,3726.0806,N,12212.2647,W,0.54,173.43,30061
5,,*17

They both use SiRF chips. Above is just the GPRMC lines. Some of them are
delayed enough to fall into the next second because every 5th second includes
the GPGSV sentences.

I'm pretty sure this was reported 3 years ago, I don't remember who found
it, but I did remember to look back to find the insertion at midnight TAI
rather than UTC.

----------

Overall, pretty boring.
Jun 30 16:59:59 shuksan klogd: Clock: inserting leap second 23:59:60 UTC

From a Z3801A:
57203 86397.032 T22015063023595830+1046
57203 86398.032 T22015063023595930+1047
57203 86399.034 T22015063023596030+103F
57203 86399.034 T22015070100000030+1025
57204 0.034 T220150701000001300102B
57204 1.032 T220150701000002300102C
57204 2.032 T220150701000003300102D

From a Z3811A:
86397.050728 T22015063023595830+0045
86398.050667 T22015063023595930+0046
86399.050712 T22015063023596030+003E
86399.050765 T22015070100000030+0024
0.050696 T220150701000001300002A
1.050750 T220150701000002300002B
2.050685 T220150701000003300002C

Google's external time servers do their smear dance at 50 ms/hour starting 10
hours before the leap. It's linear rather than a fancy cosine. I'll get a
graph together one of these days.
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Tom Van Baak
2015-07-01 15:31:32 UTC
Permalink
Hi Hal,

Am I reading this right -- those GPS receivers applied the leap second 16 seconds before they were supposed to, resulting in a double 23:59:44 instead of 23:59:59 and 23:59:60? So not only did they use GPS instead of UTC but the opted for the double second instead of a valid leap second.

/tvb

----- Original Message -----
From: "Hal Murray" <***@megapathdsl.net>
To: "Discussion of precise time and frequency measurement" <time-***@febo.com>
Cc: <***@megapathdsl.net>
Sent: Tuesday, June 30, 2015 8:38 PM
Subject: Re: [time-nuts] End Of The World
Any observations of anomalous behavior yet?
57203 86380.750 $GPRMC,235940.000,A,3726.0893,N,12212.2627,W,0.52,64.49,300615,,*20
57203 86381.748 $GPRMC,235941.000,A,3726.0889,N,12212.2627,W,0.45,78.54,300615,,*2D
57203 86383.138 $GPRMC,235942.000,A,3726.0883,N,12212.2627,W,0.82,157.71,300615,,*14
57203 86383.752 $GPRMC,235943.000,A,3726.0874,N,12212.2628,W,1.71,186.96,300615,,*1A
57203 86384.750 $GPRMC,235944.000,A,3726.0866,N,12212.2630,W,1.33,180.14,300615,,*1D
57203 86385.752 $GPRMC,235944.000,A,3726.0858,N,12212.2631,W,1.10,178.01,300615,,*13
57203 86386.751 $GPRMC,235945.000,A,3726.0850,N,12212.2632,W,1.18,179.98,300615,,*10
57203 86388.136 $GPRMC,235946.000,A,3726.0842,N,12212.2630,W,1.67,146.83,300615,,*1C
57203 86388.752 $GPRMC,235947.000,A,3726.0836,N,12212.2627,W,1.15,129.24,300615,,*19
From a MR-350P
57203 86382.186 $GPRMC,235941.000,A,3726.0808,N,12212.2649,W,0.27,67.38,300615,,*2C
57203 86382.799 $GPRMC,235942.000,A,3726.0807,N,12212.2652,W,0.37,210.08,300615,,*1A
57203 86383.805 $GPRMC,235943.000,A,3726.0811,N,12212.2647,W,0.48,95.98,300615,,*26
57203 86384.807 $GPRMC,235944.000,A,3726.0812,N,12212.2647,W,0.17,210.63,300615,,*13
57203 86385.806 $GPRMC,235944.000,A,3726.0810,N,12212.2648,W,0.29,145.10,300615,,*14
57203 86387.188 $GPRMC,235945.000,A,3726.0809,N,12212.2647,W,0.39,174.68,300615,,*1E
57203 86387.807 $GPRMC,235946.000,A,3726.0806,N,12212.2647,W,0.54,173.43,300615,,*17
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Daniel Schultz
2015-07-01 04:10:41 UTC
Permalink
I drove past the US Naval Observatory on Massachusetts Avenue in Washington
this evening. Their big LED clock by the main entrance was dark and someone
appeared to be working on it. The leap second must have broken the USNO
clock!

Dan Schultz N8FGV

---------------original message---------------
Date: Tue, 30 Jun 2015 21:03:30 -0400
From: Bob Camp <***@n1k.org>
To: Discussion of precise time and frequency measurement
<time-***@febo.com>
Subject: [time-nuts] End Of The World
Message-ID: <66D6B7A9-AA39-4D5D-8A34-***@n1k.org>
Content-Type: text/plain; charset=us-ascii

Hi

So are we all still here? Any portion of the group blasted into non-existance
by
the leap second please speak up :)

===

Any observations of anomalous behavior yet?

Bob

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Hal Murray
2015-08-05 03:36:14 UTC
Permalink
So far there have not been any home brew design radios show up that will
demodulate and lock to the new data format. There is plenty of info on the
transmit format. The demodulation approach is not crazy hard. That said,
there’s still a lot of work to get a receiver running.
Has anybody looked into a software approach? What sort of front end would
you want?
--
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Bob Camp
2015-08-05 11:15:03 UTC
Permalink
Hi

The front end would be “dealers choice”. He who does the
project gets to decide what gets used.

If you look over some other designs, you can indeed get
a device going with a 12 bit converter. The qualifier is that
the signal to noise needs to be pretty good. With fades
and switcher interference, you probably would notice its
limitations.

The “other end” of the design spectrum would be with a part
designed as a high range font end chip. You can get to a lot
of bits at low frequency. Even the prices aren’t all that crazy.

Is there one and only one approach here? Not in any way. There
are several thousand possible ways to do it. AGC or no AGC would
be a pretty major decision. Next decision would be things like clocks.
15 MHz from a ($25) KS box that also puts out 10 MHz looks like a
pretty good choice at the moment.

Past that it’s decimators / filters and the usual DSP stuff (or any of
a dozen alternatives). Given the high noise environment I’d lean towards
a DSP approach.

Most of the choices run into the easy / quick / cheap tradeoff triangle. I’m
sure that the debating process can find a solution that should “cost 10 cents”. I’m
also sure that a basement lash up of available parts is quick, but hard to reproduce.
I’m not terribly surprised at the lack of 10 cent solutions. I’m a bit surprised
that there are no unique lash up designs. The debate process seems to
have made this a pretty un-attractive thing to do.

Bob
Post by Hal Murray
So far there have not been any home brew design radios show up that will
demodulate and lock to the new data format. There is plenty of info on the
transmit format. The demodulation approach is not crazy hard. That said,
there’s still a lot of work to get a receiver running.
Has anybody looked into a software approach? What sort of front end would
you want?
--
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Graham / KE9H
2015-08-05 17:40:10 UTC
Permalink
There are several high end audio Analog to Digital Data converters that
will clock at 192 kHz, ~23 bits ENOB, which puts a 60 kHz signal sweetly in
the first Nyquist zone. Typical NF of the front end of the data converter
is 20 to 25 dB, so noise floor well below the atmospheric noise level at 60
kHz. You would only need a preamp if you were running some negative gain
antenna. Lots of dynamic range. Won't overload until 2 Volts peak-to-peak
or so. A very simple, high performance digital receiver front-end.

--- Graham / KE9H

==
Post by Bob Camp
Hi
The front end would be “dealers choice”. He who does the
project gets to decide what gets used.
If you look over some other designs, you can indeed get
a device going with a 12 bit converter. The qualifier is that
the signal to noise needs to be pretty good. With fades
and switcher interference, you probably would notice its
limitations.
The “other end” of the design spectrum would be with a part
designed as a high range font end chip. You can get to a lot
of bits at low frequency. Even the prices aren’t all that crazy.
Is there one and only one approach here? Not in any way. There
are several thousand possible ways to do it. AGC or no AGC would
be a pretty major decision. Next decision would be things like clocks.
15 MHz from a ($25) KS box that also puts out 10 MHz looks like a
pretty good choice at the moment.
Past that it’s decimators / filters and the usual DSP stuff (or any of
a dozen alternatives). Given the high noise environment I’d lean towards
a DSP approach.
Most of the choices run into the easy / quick / cheap tradeoff triangle. I’m
sure that the debating process can find a solution that should “cost 10 cents”. I’m
also sure that a basement lash up of available parts is quick, but hard to reproduce.
I’m not terribly surprised at the lack of 10 cent solutions. I’m a bit surprised
that there are no unique lash up designs. The debate process seems to
have made this a pretty un-attractive thing to do.
Bob
Post by Hal Murray
So far there have not been any home brew design radios show up that will
demodulate and lock to the new data format. There is plenty of info on
the
Post by Hal Murray
transmit format. The demodulation approach is not crazy hard. That said,
there’s still a lot of work to get a receiver running.
Has anybody looked into a software approach? What sort of front end
would
Post by Hal Murray
you want?
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Post by Hal Murray
and follow the instructions there.
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Mike Magin
2015-08-05 22:07:26 UTC
Permalink
If one were trying to use it not simply for the time code but also as a
frequency reference, it seems to me that the ideal thing would be a ADC
that can easily use an external clock (derived from a local voltage-tuned
OCXO reference under control of the SDR). Otherwise one is doing (rather
coarse) software compensation for the phase offset between the ADC clock
and the WWVB signal.

Does that make sense? Anyone know of some reasonably affordable
off-the-shelf ADC board/module that takes 10 MHz external clock?
Post by Graham / KE9H
There are several high end audio Analog to Digital Data converters that
will clock at 192 kHz, ~23 bits ENOB, which puts a 60 kHz signal sweetly in
the first Nyquist zone. Typical NF of the front end of the data converter
is 20 to 25 dB, so noise floor well below the atmospheric noise level at 60
kHz. You would only need a preamp if you were running some negative gain
antenna. Lots of dynamic range. Won't overload until 2 Volts peak-to-peak
or so. A very simple, high performance digital receiver front-end.
--- Graham / KE9H
==
Post by Bob Camp
Hi
The front end would be “dealers choice”. He who does the
project gets to decide what gets used.
If you look over some other designs, you can indeed get
a device going with a 12 bit converter. The qualifier is that
the signal to noise needs to be pretty good. With fades
and switcher interference, you probably would notice its
limitations.
The “other end” of the design spectrum would be with a part
designed as a high range font end chip. You can get to a lot
of bits at low frequency. Even the prices aren’t all that crazy.
Is there one and only one approach here? Not in any way. There
are several thousand possible ways to do it. AGC or no AGC would
be a pretty major decision. Next decision would be things like clocks.
15 MHz from a ($25) KS box that also puts out 10 MHz looks like a
pretty good choice at the moment.
Past that it’s decimators / filters and the usual DSP stuff (or any of
a dozen alternatives). Given the high noise environment I’d lean towards
a DSP approach.
Most of the choices run into the easy / quick / cheap tradeoff triangle. I’m
sure that the debating process can find a solution that should “cost 10
cents”. I’m
also sure that a basement lash up of available parts is quick, but hard to reproduce.
I’m not terribly surprised at the lack of 10 cent solutions. I’m a bit surprised
that there are no unique lash up designs. The debate process seems to
have made this a pretty un-attractive thing to do.
Bob
Post by Hal Murray
So far there have not been any home brew design radios show up that will
demodulate and lock to the new data format. There is plenty of info on
the
Post by Hal Murray
transmit format. The demodulation approach is not crazy hard. That said,
there’s still a lot of work to get a receiver running.
Has anybody looked into a software approach? What sort of front end
would
Post by Hal Murray
you want?
--
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Post by Hal Murray
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Bob Camp
2015-08-06 00:31:08 UTC
Permalink
Hi

10 MHz does not divide by an integer to 60 KHz. 15 MHz, 6 and 9 MHz are all more
reasonable candidates. The attractiveness of 15 MHz and the value of a tunable
OCXO is what makes the current $25 price of the KS boxes pretty attractive. You
*might* even be able to dispense with the tear down of the KS box and feed it 1 pps out
of your ADC / FPGA / MCU / Bailing wire rig. Instant WWVB disciplined OCXO.

Bob
Post by Mike Magin
If one were trying to use it not simply for the time code but also as a
frequency reference, it seems to me that the ideal thing would be a ADC
that can easily use an external clock (derived from a local voltage-tuned
OCXO reference under control of the SDR). Otherwise one is doing (rather
coarse) software compensation for the phase offset between the ADC clock
and the WWVB signal.
Does that make sense? Anyone know of some reasonably affordable
off-the-shelf ADC board/module that takes 10 MHz external clock?
Post by Graham / KE9H
There are several high end audio Analog to Digital Data converters that
will clock at 192 kHz, ~23 bits ENOB, which puts a 60 kHz signal sweetly in
the first Nyquist zone. Typical NF of the front end of the data converter
is 20 to 25 dB, so noise floor well below the atmospheric noise level at 60
kHz. You would only need a preamp if you were running some negative gain
antenna. Lots of dynamic range. Won't overload until 2 Volts peak-to-peak
or so. A very simple, high performance digital receiver front-end.
--- Graham / KE9H
==
Post by Bob Camp
Hi
The front end would be “dealers choice”. He who does the
project gets to decide what gets used.
If you look over some other designs, you can indeed get
a device going with a 12 bit converter. The qualifier is that
the signal to noise needs to be pretty good. With fades
and switcher interference, you probably would notice its
limitations.
The “other end” of the design spectrum would be with a part
designed as a high range font end chip. You can get to a lot
of bits at low frequency. Even the prices aren’t all that crazy.
Is there one and only one approach here? Not in any way. There
are several thousand possible ways to do it. AGC or no AGC would
be a pretty major decision. Next decision would be things like clocks.
15 MHz from a ($25) KS box that also puts out 10 MHz looks like a
pretty good choice at the moment.
Past that it’s decimators / filters and the usual DSP stuff (or any of
a dozen alternatives). Given the high noise environment I’d lean towards
a DSP approach.
Most of the choices run into the easy / quick / cheap tradeoff triangle. I’m
sure that the debating process can find a solution that should “cost 10
cents”. I’m
also sure that a basement lash up of available parts is quick, but hard to reproduce.
I’m not terribly surprised at the lack of 10 cent solutions. I’m a bit surprised
that there are no unique lash up designs. The debate process seems to
have made this a pretty un-attractive thing to do.
Bob
Post by Hal Murray
So far there have not been any home brew design radios show up that will
demodulate and lock to the new data format. There is plenty of info on
the
Post by Hal Murray
transmit format. The demodulation approach is not crazy hard. That said,
there’s still a lot of work to get a receiver running.
Has anybody looked into a software approach? What sort of front end
would
Post by Hal Murray
you want?
--
These are my opinions. I hate spam.
_______________________________________________
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Post by Hal Murray
and follow the instructions there.
_______________________________________________
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Scott Newell
2015-08-05 22:47:21 UTC
Permalink
Content-Transfer-Encoding: 8bit
There are several high end audio Analog to Digital Data converters that
will clock at 192 kHz, ~23 bits ENOB, which puts a 60 kHz signal sweetly in
the first Nyquist zone. Typical NF of the front end of the data converter
Any specific recommendations? I've seen the Asus Xonar U7 (USB) and
Asus Xonar D1 (PCI) mentioned on some of the SDR sites. (I'm running
XP and linux.)
--
newell

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Bob Camp
2015-08-06 01:55:29 UTC
Permalink
Hi

Analog Devices has some very nice ADC’s that are directly targeted at
doing this general sort of thing. They do not have any “odd” filtering approach
that creates issues. Some of the early 192 KHz audio parts did not do very well
past 1/4 the clock rate.

Bob
Content-Transfer-Encoding: 8bit
There are several high end audio Analog to Digital Data converters that
will clock at 192 kHz, ~23 bits ENOB, which puts a 60 kHz signal sweetly in
the first Nyquist zone. Typical NF of the front end of the data converter
Any specific recommendations? I've seen the Asus Xonar U7 (USB) and Asus Xonar D1 (PCI) mentioned on some of the SDR sites. (I'm running XP and linux.)
--
newell
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Graham / KE9H
2015-08-06 02:03:36 UTC
Permalink
Scott:

You won't be able to use an off-the-shelf audio card, because they will have
filters that cut off just above human hearing limits, somewhere in the
mid 20 kHz range. I was referring to the data converter chips they use
on those high end cards. The circuit for ~80 kHz (Nyquist) low pass
filters
and antenna interface would likely be a custom card.

For the guys talking about the Tayloe receivers, the Tayloe front end is
just
a down converter to get the HF or VHF signals down into the range that WWVB
is already in. So to receive WWVB, you only need the backend of the Tayloe
receiver, ie., no Tayloe mixer required. Just the (audio) data converter
and the
DSP.

--- Graham / KE9H

==
Content-Transfer-Encoding: 8bit
There are several high end audio Analog to Digital Data converters that
will clock at 192 kHz, ~23 bits ENOB, which puts a 60 kHz signal sweetly in
the first Nyquist zone. Typical NF of the front end of the data converter
Any specific recommendations? I've seen the Asus Xonar U7 (USB) and Asus
Xonar D1 (PCI) mentioned on some of the SDR sites. (I'm running XP and
linux.)
--
newell
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https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Pete Lancashire
2015-08-05 18:49:52 UTC
Permalink
There is someone on ebay selling an analog 'movement'

http://www.ebay.com/itm/181283274562

DISCLAIMER: Not associated with the seller
Post by Bob Camp
Hi
The front end would be “dealers choice”. He who does the
project gets to decide what gets used.
If you look over some other designs, you can indeed get
a device going with a 12 bit converter. The qualifier is that
the signal to noise needs to be pretty good. With fades
and switcher interference, you probably would notice its
limitations.
The “other end” of the design spectrum would be with a part
designed as a high range font end chip. You can get to a lot
of bits at low frequency. Even the prices aren’t all that crazy.
Is there one and only one approach here? Not in any way. There
are several thousand possible ways to do it. AGC or no AGC would
be a pretty major decision. Next decision would be things like clocks.
15 MHz from a ($25) KS box that also puts out 10 MHz looks like a
pretty good choice at the moment.
Past that it’s decimators / filters and the usual DSP stuff (or any of
a dozen alternatives). Given the high noise environment I’d lean towards
a DSP approach.
Most of the choices run into the easy / quick / cheap tradeoff triangle. I’m
sure that the debating process can find a solution that should “cost 10 cents”. I’m
also sure that a basement lash up of available parts is quick, but hard to reproduce.
I’m not terribly surprised at the lack of 10 cent solutions. I’m a bit surprised
that there are no unique lash up designs. The debate process seems to
have made this a pretty un-attractive thing to do.
Bob
Post by Hal Murray
So far there have not been any home brew design radios show up that will
demodulate and lock to the new data format. There is plenty of info on
the
Post by Hal Murray
transmit format. The demodulation approach is not crazy hard. That said,
there’s still a lot of work to get a receiver running.
Has anybody looked into a software approach? What sort of front end
would
Post by Hal Murray
you want?
--
These are my opinions. I hate spam.
_______________________________________________
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Post by Hal Murray
and follow the instructions there.
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Donald
2015-08-05 19:41:34 UTC
Permalink
Post by Hal Murray
So far there have not been any home brew design radios show up that will
demodulate and lock to the new data format. There is plenty of info on the
transmit format. The demodulation approach is not crazy hard. That said,
there’s still a lot of work to get a receiver running.
Has anybody looked into a software approach? What sort of front end would
you want?
I have been looking at building a "Tayloe Detector".

I have not seen any sites that have shown a 60Khz receiver based using a
Tayloe Detector tho.

If anyone has experience with this type of direct conversion receivers,
please share any experiences.

don
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Bob Camp
2015-08-05 23:36:06 UTC
Permalink
Hi

It will work as a direct conversion radio. As with any of these, the practical result
will be a tone at a lower frequency. You will convert 60 KHz to 600 Hz by using a 60.6 KHz
local oscillator. The big question is: Does this really help out or not?

Bob
Post by Donald
Post by Hal Murray
So far there have not been any home brew design radios show up that will
demodulate and lock to the new data format. There is plenty of info on the
transmit format. The demodulation approach is not crazy hard. That said,
there’s still a lot of work to get a receiver running.
Has anybody looked into a software approach? What sort of front end would
you want?
I have been looking at building a "Tayloe Detector".
I have not seen any sites that have shown a 60Khz receiver based using a Tayloe Detector tho.
If anyone has experience with this type of direct conversion receivers, please share any experiences.
don
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Jim Lux
2015-08-06 00:44:05 UTC
Permalink
Post by Donald
Post by Hal Murray
So far there have not been any home brew design radios show up that will
demodulate and lock to the new data format. There is plenty of info on the
transmit format. The demodulation approach is not crazy hard. That said,
there’s still a lot of work to get a receiver running.
Has anybody looked into a software approach? What sort of front end would
you want?
I have been looking at building a "Tayloe Detector".
I have not seen any sites that have shown a 60Khz receiver based using a
Tayloe Detector tho.
I'm not sure it would buy you much.. you'd have something running at
240kHz switching the inputs to the detector?

It's MUCH easier to just digitize the 60kHz with a high resolution
converter. And have a nice BPF in front of the digitizer.

The tayloe/quadrature sampling detector (a key part of the Flexradio
original design) is more convenient if you're making a direct conversion
receiver that needs to tune up to 10s of MHz, since it allows you to use
a slow ADC with lots of bits. It's basically a I/Q mixer and will take
a lot more parts in total than just getting a 192ksps 24 bit converter.
Post by Donald
If anyone has experience with this type of direct conversion receivers,
please share any experiences.
don
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Donald
2015-08-06 03:03:05 UTC
Permalink
Post by Jim Lux
I'm not sure it would buy you much.. you'd have something running at
240kHz switching the inputs to the detector?
It's MUCH easier to just digitize the 60kHz with a high resolution
converter. And have a nice BPF in front of the digitizer.
The tayloe/quadrature sampling detector (a key part of the Flexradio
original design) is more convenient if you're making a direct
conversion receiver that needs to tune up to 10s of MHz, since it
allows you to use a slow ADC with lots of bits. It's basically a I/Q
mixer and will take a lot more parts in total than just getting a
192ksps 24 bit converter.
Thanks for the numbers.

I was uncertain how to scale the sample rate for the I/Q.

Don


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