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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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?
--
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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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Donald
2015-08-06 03:27:43 UTC
Permalink
Post by Bob Camp
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.
What type of FFT horse power would be needed at 192 Khz ?

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Bob Camp
2015-08-06 11:02:24 UTC
Permalink
Hi
Post by Donald
Post by Bob Camp
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.
What type of FFT horse power would be needed at 192 Khz ?
A ~$30 FPGA card plus an MCU would be massive overkill. It would also be fairly
easy to do. A similarly priced ARM board from any of a dozen outfits
*might* do the trick. I’d do it with:

Analog Devices ADC as a front end clocked at ~ 240 KHz
FPGA board to decimate and filter the ADC samples
ARM board to do the time code -> OCXO stuff and user display.

Could you get away without this or that? Who knows. There isn’t
enough cost in any of those “chunks” to really matter compared
to the months of effort this would take.

If I was going to do the front end with what I have sitting here, I’d probably use
the AD7660 clocked at 1.5 MHz (15 / 10 out of the KS box) or one of it’s slower
cousins clocked some other way.

Bob
Post by Donald
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Jim Lux
2015-08-06 17:43:45 UTC
Permalink
Post by Donald
Post by Bob Camp
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.
What type of FFT horse power would be needed at 192 Khz ?
not very much..

It's a fairly narrow band signal, It might be more computationally
efficient to do a Bandpass FIR and decimate.


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Bob Camp
2015-08-07 01:51:43 UTC
Permalink
Hi
Post by Jim Lux
Post by Donald
Post by Bob Camp
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.
What type of FFT horse power would be needed at 192 Khz ?
not very much..
It's a fairly narrow band signal, It might be more computationally efficient to do a Bandpass FIR and decimate.
If you have an FPGA to do the “lots of bits” add(s), a higher order decimator followed by a filter probably will do just fine.
With some care you can get a few hundred db of filtering that way (math wise). Even without much thought, you can get
past 150 db. You likely will hit IMD issues on your ADC *long* before that. The decimator (which is computationally simple)
does all the high speed heavy lifting. The filter(s) run(s) at a much slower rate so it’s not terribly MIPS intensive.

Bob
Post by Jim Lux
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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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David G. McGaw
2015-08-06 10:24:08 UTC
Permalink
That is not true. If the converter is set to 192kHz sampling, the
bandwidth will be nearly 96kHz, typically at least 80kHz, not limited to
20kHz. That is the POINT of 192kHz sampling.

David N1HAC
Post by Graham / KE9H
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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Graham / KE9H
2015-08-06 23:03:59 UTC
Permalink
As long as there is no analog audio bandwidth Nyquist filter, or it is
digital and scales with the sampling frequency, then I agree.
--- Graham

==
Post by David G. McGaw
That is not true. If the converter is set to 192kHz sampling, the
bandwidth will be nearly 96kHz, typically at least 80kHz, not limited to
20kHz. That is the POINT of 192kHz sampling.
David N1HAC
Post by Graham / KE9H
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
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
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
2015-08-07 01:41:18 UTC
Permalink
Hi


Well, at least *some* of the chips out there do not make it to 96 KHz when sampling at 192 KHz. It’s
been a few years since I dug into them. Back then a chip that had an internal filter that went to 96K
was very much the exception rather than the rule. If the only point of 192K is getting to a 96K bandwidth,
a lot of the chip guys missed out on it ….


Bob
That is not true. If the converter is set to 192kHz sampling, the bandwidth will be nearly 96kHz, typically at least 80kHz, not limited to 20kHz. That is the POINT of 192kHz sampling.
David N1HAC
Post by Graham / KE9H
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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Charles Steinmetz
2015-08-07 06:18:20 UTC
Permalink
Post by Bob Camp
Well, at least *some* of the chips out there do
not make it to 96 KHz when sampling at 192 KHz. It’s
been a few years since I dug into them. Back
then a chip that had an internal filter that went to 96K
was very much the exception rather than the
rule. If the only point of 192K is getting to a 96K bandwidth,
a lot of the chip guys missed out on it ….
192k *audio* ADCs often have input anti-aliasing
filters that are only 20-50kHz wide. In that
case, the point of sampling at 192ks/S is so the
anti-aliasing filter does not need to have a
brick wall response (as it would need to have if
you sampled at 48 or even 96ks/S), so it can have
a flatter group delay over the range of human hearing.

For this and a number of other good reasons
(large variations in gain, large DC errors, and
idle tones, to name just three), one does not
generally want to use audio ADCs (or DACs) for
non-audio applications even if there is not an
internal input filter -- tempting as it may seem
because they make bazillions of the audio parts
and they are cheap. That's what they make "industrial" ADCs and DACs for.

Best regards,

Charles



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Iain Young
2015-08-08 07:29:18 UTC
Permalink
Post by Bob Camp
Well, at least *some* of the chips out there do not make it to 96 KHz
when sampling at 192 KHz. It’s
been a few years since I dug into them. Back then a chip that had an
internal filter that went to 96K
was very much the exception rather than the rule. If the only point of
192K is getting to a 96K bandwidth,
a lot of the chip guys missed out on it ….
192k *audio* ADCs often have input anti-aliasing filters that are only
20-50kHz wide. In that case, the point of sampling at 192ks/S is so the
anti-aliasing filter does not need to have a brick wall response (as it
would need to have if you sampled at 48 or even 96ks/S), so it can have
a flatter group delay over the range of human hearing.
I guess I got lucky. The machine I brought specifically for SDR work
ended up with an (on board) 192kHz sample card, that appears not to have
such filters in.

Loading Image... and Loading Image...

You should be able to spot MSF and DCF booming in amongst the low data
LF stations (and odd sprog). This is off my LF antenna, but a long wire
may be sufficient

(In fact a 2M long feed wire to the mic socket was picking up both time
signals by itself for me, but that's another story!)

While not decoding the phase, my gnuradio MSF and DCF receivers are
here: http://hal.g7iii.net/GRC/Radio_Clocks/

I do have a gnuradio TDF decoder as well if anyone is interested. TDF
twiddles the phase on a AM carrier to transmit the time. Originally I
simply used an LPF, but then switched to using the Quadrature Demod
block which was available in gnuradio


Iain
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John Ackermann N8UR
2015-08-07 17:08:37 UTC
Permalink
If anyone is really interested in an SDR WWVB receiver project, TAPR has
a fairly large quantity of boards left over from a previous project that
use a very high performance 192ksample sound card chip (AK5394) in a
carefully laid-out design with no filtering (I believe the inputs are
also DC coupled). The board also has a CPLD which might be repurposed
(don't know if it's big enough to be useful).

The downside is that the board talked directly to the application
software, so there are no OS-level drivers available.

We would love to find a use for these boards, and could probably make a
nice deal if someone wanted to use them in a project.

Here's a link to some information:
http://openhpsdr.org/wiki/index.php?title=JANUS

Contact me off-line if you're interested or have further questions.

John
----
Post by Bob Camp
Hi
Well, at least *some* of the chips out there do not make it to 96 KHz when sampling at 192 KHz. It’s
been a few years since I dug into them. Back then a chip that had an internal filter that went to 96K
was very much the exception rather than the rule. If the only point of 192K is getting to a 96K bandwidth,
a lot of the chip guys missed out on it ….
Bob
That is not true. If the converter is set to 192kHz sampling, the bandwidth will be nearly 96kHz, typically at least 80kHz, not limited to 20kHz. That is the POINT of 192kHz sampling.
David N1HAC
Post by Graham / KE9H
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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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?
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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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Jim Lux
2015-08-06 17:54:06 UTC
Permalink
Post by Donald
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.
if you want to turn a regular single channel data stream and turn it
into IQ, an easy way is to do the ++-- approach.

complex sample 1 = real sample 1 + j real sample 2
complex sample 2 = -real sample 3 - j real sample 4
complex sample 3 = real sample 5 + j real sample 6
complex sample 4 = -real sample 7 - j real sample 8
and so forth..

This will give you an I/Q sample stream centered at samplingrate/4. So
for 192 ksps (real), fs/4 = 48 kHz, so your 60 kHz signal will be at an
apparent frequency of +12 kHz (sampled at 96k i/q samples/sec)

As mentioned in a different post, I'd look at a filter/decimate, which
might be computationally faster. Say you need 1kHz bandwidth (which I
think is pretty wide for WWVB)
http://www.nist.gov/pml/div688/grp40/upload/Bin-2719.pdf


so you're looking at 192:1 decimation. with 192 taps, I'll bet you can
make a fairly decent BPF (and if you're clever, probably bring 60kHz
down to close to DC at the same time, by combining a synthetic LO with
the taps)

So you'd be looking at 192 multiplies and adds per 1kHz output point,
which is a pretty "loafing along" CPU load (e.g. a whole lot of
microcontrollers could do it)

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Brian Inglis
2015-08-07 14:13:42 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?
WWVB is a 1 baud trinary (0/1/marker) AM signal which goes low at the start of the
second and goes high after 200ms, 500ms, or 800ms, and a 1 baud binary PM signal
with possible phase inversion on the carrier 100ms after the start of each second.

Given a $10 60kHz receiver, the AM data should be readable by any UART running at
10bps, with 1 start bit, 8 data bits including Mark parity, 1 stop bit.
Each "character" could then be decoded into one of the three symbols transmitted.

If all you want is the PPS and AM time code, it can also be done with an 8kHz
audio codec. The NTP CHU ref clock driver will decode CHU Bell 103 300bps
signals in software.

For the PM signal, you need an LF receiver and a detector for the possible phase
change before and after 100ms after PPS to extract the binary data.
--
Take care. Thanks, Brian Inglis
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Donald
2015-08-07 20:43:10 UTC
Permalink
Post by Brian Inglis
Given a $10 60kHz receiver,
This is the problem.

I can not find $10 receivers any more.

I can find $15-$20 receivers (from the UK), add shipping and it minimum
$20+.

Even the older chips still work with the new format, its just finding
them, cheaply.

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Brian Inglis
2015-08-08 17:50:52 UTC
Permalink
Post by Donald
Post by Brian Inglis
Given a $10 60kHz receiver,
This is the problem.
I can not find $10 receivers any more.
I can find $15-$20 receivers (from the UK), add shipping and it minimum $20+.
Even the older chips still work with the new format, its just finding them, cheaply.
US sources probably have low demand - so 10 euro/pound now - possibly as much for shipping
- Scott Newell's post gives sites - found these search filters show the items of interest:
http://www.pvelectronics.co.uk/index.php?main_page=advanced_search_result&search_in_description=1&keyword=wwvb
http://www.hkw-shop.de/index.php?cl=search&searchparam=60khz
- see what S&H come to.
--
Take care. Thanks, Brian Inglis
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Hal Murray
2015-08-06 04:48:42 UTC
Permalink
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.
Has anybody investigated the signals on the cable between the two boxes?

The status screen on the non-gps box shows the GPS info so it's more than
just a PPS going across.
--
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Hal Murray
2015-08-07 04:05:17 UTC
Permalink
Post by Bob Camp
A ~$30 FPGA card plus an MCU would be massive overkill. It would also be
fairly easy to do. A similarly priced ARM board from any of a dozen outfits
*might* do the trick.
...
Post by Bob Camp
Could you get away without this or that? Who knows. There isn’t enough cost
in any of those “chunks” to really matter compared to the months of effort
this would take.
If I was worried about the "months" to get things working, I'd avoid the FPGA
and do everything in software.
--
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Bob Camp
2015-08-07 21:57:00 UTC
Permalink
Hi
Post by Hal Murray
Post by Bob Camp
A ~$30 FPGA card plus an MCU would be massive overkill. It would also be
fairly easy to do. A similarly priced ARM board from any of a dozen outfits
*might* do the trick.
...
Post by Bob Camp
Could you get away without this or that? Who knows. There isn’t enough cost
in any of those “chunks” to really matter compared to the months of effort
this would take.
If I was worried about the "months" to get things working, I'd avoid the FPGA
and do everything in software.
Actually the FPGA is pretty fast. I doubt it will take more than 20% of the time the
software that goes with the FPGA will take. Without the FPGA I suspect the pure
software approach will take about 4X longer than FPGA + software.

Been there done that ...

Bob
Post by Hal Murray
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Hal Murray
2015-08-07 08:40:27 UTC
Permalink
Post by Bob Camp
Well, at least *some* of the chips out there do not make it to 96 KHz when
sampling at 192 KHz. It’s been a few years since I dug into them. Back then
a chip that had an internal filter that went to 96K was very much the
exception rather than the rule. If the only point of 192K is getting to a
96K bandwidth, a lot of the chip guys missed out on it 
.
Where did 192 KHz come from? Why is anybody interested in anything that far
over 2*44 KHz?

It's common to have an audio ADC run much faster than Nyquist, but that's a
hack to make it easier to build the cut off filter. You build a simple
analog filter and a sharp digital filter and decimator so the output is 2x
the target frequency. You get what you want without a fancy analog filter.
--
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Jim Lux
2015-08-07 23:02:56 UTC
Permalink
Post by Hal Murray
Post by Bob Camp
Well, at least *some* of the chips out there do not make it to 96 KHz when
sampling at 192 KHz. It’s been a few years since I dug into them. Back then
a chip that had an internal filter that went to 96K was very much the
exception rather than the rule. If the only point of 192K is getting to a
96K bandwidth, a lot of the chip guys missed out on it ….
Where did 192 KHz come from? Why is anybody interested in anything that far
over 2*44 KHz?
There's lots of high resolution parts at that rate..
And if it's that fast, odds are the built in sample/track/hold is good
enough that you could directly sample the 60kHz without much trouble.

With a slower ADC and a good analog BPF and a good sample/hold, you
could sample at a few kHz, but that shifts the design burden to the BPF
and the sample/hold.
Post by Hal Murray
It's common to have an audio ADC run much faster than Nyquist, but that's a
hack to make it easier to build the cut off filter. You build a simple
analog filter and a sharp digital filter and decimator so the output is 2x
the target frequency. You get what you want without a fancy analog filter.
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Clint Turner
2015-08-07 22:30:06 UTC
Permalink
Hi Bob,

The use of the PIC for WWVB carrier/data detection was only ever
intended for use with a visual clock, thus uncertainty (e.g. lag, delay
or whatever you want to call it) was par for the course in the
implementation that I described.
Hi
The gotcha with under sampling is the need for tight bandpass filters in front of the sampler. Narrow bandwidth always
equates to long delay. If the filters are analog (rather than digital) that delay will have drift and temperature sensitivity.
Both of those things are to be avoided (if possible) in a receiver intended for high accuracy use.
Bob
Neil, as for the link below, unfortunately that's not it. The project
in question used the PIC's A/D converter to directly process the
signal. This would rule out the PIC16F84 used in the link, below, as
that has no A/D capability. I've looked some more and have still been
unable to find it: I'm sure that it's on the Wayback Machine somewhere,
but things can be tricky to find if you don't already have a URL!
Clint,
Is this the design you are looking for?
http://webpages.charter.net/ekyle/WWVB.html
-Neil
I did see a mention of a "Tayloe" detector (or "QSD" - Quadrature
Sampling Detector) that might also be used to advantage in a project
like this. As with A/D converters, they, too may be undersampled with
reasonable effect - Some of the readily-available SDR receiver kits do
this - so it should be very practical to do something like the following:

- Produce an audio/sine wave DDS in software using the PWM hardware in
the processor (PIC, Arduino) at 4x the desired frequency using outboard
low-pass filtering.
- Slice it using the processor's onboard comparator or an outboard: Many
PICs have comparators with outputs that may be made external.
- Apply this sliced signal to a divide-by-four system or counter to
produce the quadrature signal, or use the interrupt from the comparator
have the processor produce a count on a pair of pins for a multi-channel
analog switch.
- Use a QSD (a.k.a. Tayloe) to yield "baseband" at/around DC.
- Apply said baseband quadrature output to a pair of A/D inputs. If the
A/D's are sampled in quick succession compared to the detection
bandwidth, reasonable balance could be maintained.

Again, the QSD could be operated at a fraction of the desired frequency
using undersampling techniques provided that the input was adequately
bandpass-filtered - but this would seem like overkill since
undersampling using the A/D converter could accomplish practically the
same thing and the quadrature channels (or Costas) be done in software.

* * *

Taking a different approach, one could feed the sine output (at audio
frequencies) to a plain-old 4046 VCO/PLL and multiply the audio
frequency to 4x the receive frequency (240 kHz for WWVB, 310 kHz for
DCF77, etc.) and then produce the quadrature clocks for a direct
conversion at-frequency, the advantage being that there would need not
be any particular bandpass filtering in front of the QSD - just standard
low-pass filtering - to produce the baseband/quadrature outputs. The
phase/jitter incurred by the squaring/frequency multiplication would be
largely irrelevant in the long-term detection windows involved.

An audio-frequency DDS synthesizer with 32 bit accumulator resolution is
very easy to produce in software and with microHertz tuning resolution,
very fine phase control may be achieved in the long term: I've used
PIC-based audio DDS generators referenced from stabilized oscillators to
produce references to synthesize VHF frequencies as well as discipline
VHF/UHF oscillators with excellent results - with special steps taken to
mitigate phase modulation issues - so such should be practical at 60 kHz
with trivial hardware. (See links below for information on using audio
DDS techniques with respect to VHF oscillators.)

What would produce delay/uncertainty would be the necessary lowpass
filtering on the output of the QSD needed to limit the detection
bandwidth, but some of this could be mitigated with multiple windowed
detectors (in software), stable analog components and appropriate
characterization of the circuits involved.

It is probably fair to say that given the limited detection bandwidth
and, more importantly, the rather limited processing resources of a
low-end processor one will never quite achieve the same timing accuracy
that one might get with long-term correlation techniques to determine
the phase reversal of the original carrier down to the half-cycle -
minus propagational uncertainties, of course!

(One would have to be nuts to want to do all of this, but that's half of
the name of this group!)


73,

Clint
KA7OEI

References for using PIC-generated DDS audio signals as references for
VHF oscillators:

- http://www.ka7oei.com/wxsat.html
- http://utaharc.org/rptr/synchronous_62.html - using the same DDS
techniques to discipline VCXOs.


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Donald
2015-08-08 03:33:42 UTC
Permalink
( very detailed explanation snipped )
Thank You for your explanation, I had thought of this as well, but I do
not know enough to implement this.

Looking at the WWVB chips that were available, what might it take to
make a discrete version of those designs ??

Thanks


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Bob Camp
2015-08-08 17:16:58 UTC
Permalink
HI

Discrete as in resistors and transistors or discrete as in “stuff plus an MCU”?

Bob
( very detailed explanation snipped )
Thank You for your explanation, I had thought of this as well, but I do not know enough to implement this.
Looking at the WWVB chips that were available, what might it take to make a discrete version of those designs ??
Thanks
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paul swed
2015-08-09 16:20:57 UTC
Permalink
I looked at the site its the typical cmall board with everything on it.
Saves you the trouble of doing that very fine soldering.
No antenna.
Regards
Paul
WB8TSL
Post by Bob Camp
HI
Discrete as in resistors and transistors or discrete as in “stuff plus an MCU”?
Bob
Post by Donald
( very detailed explanation snipped )
Thank You for your explanation, I had thought of this as well, but I do
not know enough to implement this.
Post by Donald
Looking at the WWVB chips that were available, what might it take to
make a discrete version of those designs ??
Post by Donald
Thanks
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Bob Camp
2015-08-09 18:01:04 UTC
Permalink
Hi

Like it or not, the world is going to BGA’s. Even the “fine pitch” leaded stuff
is slowly going away. You might or might not like soldering a fine pitch IC.
Doing a BGA at home - sorry, not for me. I doubt it’s on the “fun list” for
anybody else either. We had better all get used to the idea that a part on a
board is the “smallest unit of construction” for this or that project.

Thankfully the fine people far over the ocean seem to be able to put a part
on a board for less money than I can buy the raw part. They as a group also seem to
deliver a working (though maybe a bit messy) part every time I’ve got this or
that. Hook a couple boards up and *poof* instant project. Even mounted to a
board the stuff is still tiny. Unless you are doing a “wearable” project it’ll be
plenty small enough.

Go for the board, it’s the way you do a prototype these days !! That’s every bit as true
at work as it is at home ….

Bob
Post by paul swed
I looked at the site its the typical cmall board with everything on it.
Saves you the trouble of doing that very fine soldering.
No antenna.
Regards
Paul
WB8TSL
Post by Bob Camp
HI
Discrete as in resistors and transistors or discrete as in “stuff plus an MCU”?
Bob
Post by Donald
( very detailed explanation snipped )
Thank You for your explanation, I had thought of this as well, but I do
not know enough to implement this.
Post by Donald
Looking at the WWVB chips that were available, what might it take to
make a discrete version of those designs ??
Post by Donald
Thanks
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Donald
2015-08-09 19:54:18 UTC
Permalink
On 8/9/2015 12:01 PM, Bob Camp wrote:
< snip >

Back to my original comment, These boards and chips are no longer
available in the US.
From the UK I have purchased some older boards and they do work as
described.

After all the discussion, I guess WWVB is no longer a profitable market.
Buying boards from far away is all that's left.

Thanks to all that responded, I just take the easy (and costly) way out.

Don
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Bob Camp
2015-08-09 21:02:45 UTC
Permalink
Hi

Maybe a little more on “why demodulate the phase mod?”.

1) The signal to noise of the recovered data stream will be significantly
better with the phase mod data. The NIST paper is correct about that.
That alone makes it a neat thing.

2) The interference rejection of the phase mod approach is better. This
is a bigger deal in some parts of the country than others. Night time MSF rejection
is not easy here in the Northeast ...

3) You need to demodulate (to some degree) the phase mod to implement
a “frequency reference” receiver. All the fine old ones no longer work directly
with the current WWVB signal.

4) There is more information in the phase mod signal than in the AM modulation
data stream. It would be fun / useful to have access to that data.

5) The last crop of precision receivers came out several decades ago. There
are a *lot* of things you could try today that simply did not make (economic) sense
back then. Propagation prediction based on location, season, and time of day would be
pretty high up on that list.

6) A whole lot has happened in the world of amateur SDR that *could* apply to this sort
of receiver. This is at the “cheap and slow” end of the world. That makes applying
a digital radio a whole lot easier than at microwaves.

7) A lot of us grew up with phase comparison (either WWVB or Loran-C) as
a method of calibrating / evaluating frequency standards. It’s a technique that
is know to work. It may not be of interest to the word at large. It is of interest
to a number of people here on the list.

8) You might learn something by building a receiver like this. Can you detect
the phase transitions to X,XXX us or to XX.X ns? who knows. Can you better
catch cycle slips with the help of the phase mod? Again, unknown until the
receiver is up and running.

9) GPSDO’s are an outgrowth of the original WWVB ( or more generaly VLF)
disciplined standards. We (or at least I) now have piles of these GPSDO things
taking up room in the front hall. They are getting pretty cheap. Using some of
what has been learned in that arena (and some of the hardware) to improve a
WWVB approach is a real possibility.

10) Since GPSDO’s are all over the place. You *can* use one as a reference
for a lot of the development of a WWVB device. We don’t all have to move into
Tom’s basement and “borrow” the H-Maser signal in order to get one going.

Bottom line it’s a “basement compatible” project. It’s not massively expensive. It
does not require “nutty” levels of instrumentation. You can go as far as you desire
towards the full list of bells and whistles. Compared to other “Time Nut” grade projects
it’s towards the simple end of the list. (Consider that home built H-Masers, DIY Rb’s,
Ion clocks, and Cs fountains have been suggested in the past). It’s a *lot* of work and
by no means trivial to do. I’d say it’s worth trying.

Bob
Post by Donald
< snip >
Back to my original comment, These boards and chips are no longer available in the US.
From the UK I have purchased some older boards and they do work as described.
After all the discussion, I guess WWVB is no longer a profitable market.
Buying boards from far away is all that's left.
Thanks to all that responded, I just take the easy (and costly) way out.
Don
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Donald
2015-08-09 18:11:13 UTC
Permalink
Post by Bob Camp
HI
Discrete as in resistors and transistors or discrete as in “stuff plus an MCU”?
To be clear(er):

This data sheet is one of a few receivers from a few vendors:
http://www.datasheetcatalog.com/datasheets_pdf/U/4/2/2/U4221B.shtml

Looking at the data sheet link shows the internals of the receiver chip.

This chip outputs the serial stream of the WWVB pwm data.

From there any MCU can decode that stream via bit-bang.




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Bob Camp
2015-08-09 20:16:43 UTC
Permalink
Hi

Ok, that’s a 20 year old IC. When it talks about doing WWVB, it’s talking about
the AM modulation format. It’s not talking about the new phase modulation approach.
These are the chips that probably will disappear completely once the chips for the newer format
show up.

Bob
Post by Donald
Post by Bob Camp
HI
Discrete as in resistors and transistors or discrete as in “stuff plus an MCU”?
http://www.datasheetcatalog.com/datasheets_pdf/U/4/2/2/U4221B.shtml
Looking at the data sheet link shows the internals of the receiver chip.
This chip outputs the serial stream of the WWVB pwm data.
From there any MCU can decode that stream via bit-bang.
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Donald
2015-08-09 22:56:43 UTC
Permalink
Post by Bob Camp
Hi
Ok, that’s a 20 year old IC. When it talks about doing WWVB, it’s talking about
the AM modulation format. It’s not talking about the new phase modulation approach.
These are the chips that probably will disappear completely once the chips for the newer format show up.
This has been discussed on time-nuts before:
https://www.febo.com/pipermail/time-nuts/2014-July/085445.html

A few months ago I too contacted Everset about getting some chips.

So over a year has passed and the new chips are not available.

Which is why asked for a "simple receiver",

Another discussion talks about the patent Everset has, I do not think
others will be joining the party.

The chip I chose is one of many 20 year old chips.
Except the Everset chip, there have been no new chips developed in over
20 years.

As they say in the old country, "Oh well"

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Bob Camp
2015-08-09 23:40:49 UTC
Permalink
Hi
Post by Donald
Post by Bob Camp
Hi
Ok, that’s a 20 year old IC. When it talks about doing WWVB, it’s talking about
the AM modulation format. It’s not talking about the new phase modulation approach.
These are the chips that probably will disappear completely once the chips for the newer format show up.
https://www.febo.com/pipermail/time-nuts/2014-July/085445.html
A few months ago I too contacted Everset about getting some chips.
So over a year has passed and the new chips are not available.
Which is why asked for a "simple receiver",
Another discussion talks about the patent Everset has, I do not think others will be joining the party.
The chip I chose is one of many 20 year old chips.
Except the Everset chip, there have been no new chips developed in over 20 years.
I have a watch on my wrist and a clock on the wall. Both synch to WWVB. They use chips to do this.
The silicon in the watch came out about 4 years ago. The chip in the clock is about 7 years old.
The watch chip is now obsolete and has been replaced by a newer one. I have not taken a hammer
to a newer clock to see what they are now using. New chips for WWVB are very much being actively
designed all the time. They integrate a *lot* of functions in the chip beyond a simple receiver.

Bob
Post by Donald
As they say in the old country, "Oh well"
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Donald
2015-08-10 02:38:29 UTC
Permalink
I wish to thank you all for the information presented here about WWVB
receivers.


A few years ago I had been building some LED clocks for friends, more
art then electronics.
Those clocks had a WWVB receiver I got from Digikey.

Today I am re-visiting those clocks as Word Clocks.
Letters instead of numbers forming words, I am sure you have seen them
around.

People keep saying there are WWVB chips available, but I can not find
any chips.
When I ask for information about these chips, no response.
I have asked about discrete designs and Digital designs, no response.
I am not able to design these myself. So any tangible information would
help.

Ok, I can not get chips/modules here in the US.
I do find modules from Europe and China.

I am in Boulder, Colorado.
This is where Sparkfun is located.
I asked them about the receiver modules they had carried for years,
They said they can not get them any more, OK.

But why ?

Nobody knows.

Digikey won't even answer my emails about them.

I had asked a China manufacture for 2 units, but they can not sell me 2
units.
But if I buy 20 units (I would be a manufacture) then they can sell them
to me.

So, bottom line.

I can only get modules from Europe/China at $20 each.

OK.

If I have come across too <pick your favorite term>, I apologize.

I thought this would be a simple question with a simple answer.

On another note, I have found a WiFi module for $3.00 and I can connect
to an NNTP server.
ESP-8266, if you need a serial to WiFi connection.

I will re-start my project with a new direction.

Thank You for your response.

Don

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Tom Van Baak
2015-08-09 20:20:55 UTC
Permalink
Post by Donald
http://www.datasheetcatalog.com/datasheets_pdf/U/4/2/2/U4221B.shtml
Looking at the data sheet link shows the internals of the receiver chip.
This chip outputs the serial stream of the WWVB pwm data.
From there any MCU can decode that stream via bit-bang.
Hi Don,

About the U4221B -- that TEMIC series was widely used in WWVB receivers 15 to 20 years ago. The problem for many hobbyists today is that these very nice chips have long since been out of production. Note the May '96 date on the datasheet.

I figure there minimal low-volume demand -- just not enough WWVB hobbyists in the world. And for high-volume -- companies like Sony, Seiko, Casio, and Junghans typically roll their own chips, one where they can fully integrate the receiver into the single IC that does everything else: clock, calendar, display, subcode decode, motor control, power management (solar charge).

WWVB RCC (radio controlled clocks) and watches have evolved -- many companies now offer "multi-band" clocks that automatically handle all the world-wide LF broadcasts (WWVB,JJY40/60,MSF,DCF77). This further lowers the market demand for a WWVB-only plain receiver IC.

Under my http://leapsecond.com/pages/sony-wwvb/ page is a full set of vintage Temic datasheets:

http://leapsecond.com/pages/sony-wwvb/U4221B-96.pdf
http://leapsecond.com/pages/sony-wwvb/U4223B-97.pdf
http://leapsecond.com/pages/sony-wwvb/U4224B-98.pdf
http://leapsecond.com/pages/sony-wwvb/T4225B-96.pdf
http://leapsecond.com/pages/sony-wwvb/U4226B-98.pdf
http://leapsecond.com/pages/sony-wwvb/

And lastly, this old Temic time code document is a must-read for anyone playing with RC clocks:

http://leapsecond.com/pages/sony-wwvb/timeco-97.pdf

/tvb

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Bob Camp
2015-08-09 23:33:07 UTC
Permalink
Hi

If you never have tried to keep an IC in production, there are some basic things
that may not be very obvious:

1) Chip geometries shrink fast. A 4 year old production geometry is essentialy obsolete.
2) Manufacturing lines either are retired or re-tooled to the new rules on a regular basis
a line that is still running the same process and gear it had 4-6 years ago is a rarity.
3) Digital stuff shrinks with some fairly simple rules. You still pay (big) bucks to
re-tool the masks for the new process. That phone call comes in about every 4 years.
4) Analog stuff does not shrink with simple rules. You re-model and (effectively)
redesign the part each time you change process. Add that on top of the charges
for the digital process.

You would *think* that keeping an old like open would make sense. Basic math
unfortunately is not on your side. Make 1/10 as many chips on that line (and 1/10 the
batch sizes) and the cost goes through the roof. That’s fine for those who can afford
to pay $100 for a chip that used to cost $2. For the rest of us, not so good a solution.

No matter how cool all the design rules get, you still have to go dice the wafer. That’s a
process that does not shrink much with time. There is a minimum size they can dice a wafer
down to. The same ~1 mm x 1 mm rule works today that worked back in 1970. If you have a
function that uses one gate, it’s still going to be on a minimum sized die.

The new process costs less per transistor than the old process. It probably costs more per square
yard of silicon. A chip that made sense at some number of devices on the old process makes
more sense at 4X that number of devices on the new process. Effectively you get a bunch
more capability for free on a minimum sized die.

A consumer IC will sell in the “> thousands per day” range at it’s peak. A successful IC will sell
at a 10X multiple past that. That’s what gets the prices down to the level that we get used
to seeing. Drop back to <50K a year and you get a phone call from the foundry about “last
time buy”.

Can you move your gizmo to a new foundary when you get that call? Sure you can. Expect
to pay for new masks and all the modeling runs that go with them. There’s a couple of bucks
onto the price of each IC you make.

If you are selling into a cost sensitive application, (and who isn’t), the expectation is that the price
of components comes down at a fairly steep rate every quarter (or at least every year). Start bumping
the price up and your customer is going to look for an alternative. Down goes volume some more.

None of this even begins to get into the test and quality assurance part of keeping an IC going. It
also does not look at things like field support, inventory, and marketing. None of those things are
free.

That all seems a bit much. It’s not. I’ve been in the middle of a *lot* of these phone calls
over the years. There’s been a lot of money spent on new masks and redesigns. The amazing
thing is not that IC’s go out of production on a regular basis. The amazing thing is that any of them
stay IN production for more than 8 or 10 years.

The net result is pretty much always that the simple old devices get replaced with ever more
complex new alternatives. The new ones may be harder to find for a basement hobbyist . The guys
who use them in volume know right were to get them. The volume of basic IC’s has been dropping
for years and will continue to do so. (That’s in pieces, in dollars … wow!)

Bob
Post by Tom Van Baak
Post by Donald
http://www.datasheetcatalog.com/datasheets_pdf/U/4/2/2/U4221B.shtml
Looking at the data sheet link shows the internals of the receiver chip.
This chip outputs the serial stream of the WWVB pwm data.
From there any MCU can decode that stream via bit-bang.
Hi Don,
About the U4221B -- that TEMIC series was widely used in WWVB receivers 15 to 20 years ago. The problem for many hobbyists today is that these very nice chips have long since been out of production. Note the May '96 date on the datasheet.
I figure there minimal low-volume demand -- just not enough WWVB hobbyists in the world. And for high-volume -- companies like Sony, Seiko, Casio, and Junghans typically roll their own chips, one where they can fully integrate the receiver into the single IC that does everything else: clock, calendar, display, subcode decode, motor control, power management (solar charge).
WWVB RCC (radio controlled clocks) and watches have evolved -- many companies now offer "multi-band" clocks that automatically handle all the world-wide LF broadcasts (WWVB,JJY40/60,MSF,DCF77). This further lowers the market demand for a WWVB-only plain receiver IC.
http://leapsecond.com/pages/sony-wwvb/U4221B-96.pdf
http://leapsecond.com/pages/sony-wwvb/U4223B-97.pdf
http://leapsecond.com/pages/sony-wwvb/U4224B-98.pdf
http://leapsecond.com/pages/sony-wwvb/T4225B-96.pdf
http://leapsecond.com/pages/sony-wwvb/U4226B-98.pdf
http://leapsecond.com/pages/sony-wwvb/
http://leapsecond.com/pages/sony-wwvb/timeco-97.pdf
/tvb
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Jim Lux
2015-08-10 01:11:30 UTC
Permalink
Post by Bob Camp
Hi
If you never have tried to keep an IC in production, there are some basic things
<snip>
There's always Rochester Electronics.. "leaders in the trailing edge"
(no kidding, that's their slogan)..

They buy old fabs, masks, etc, and keep producing small runs of older
parts. For a price.

At some point, multiproject wafers (like MOSIS) might become a hobby
product. So far, it's in the "several kilobuck" minimum purchase, and,
as well, the tools aren't easy to come by. Or, more properly, good
design tools are expensive, tedious design tools are free.. you CAN
layout an IC for MOSIS with a ruler and and a quadrille pad.. get your
copy of Carver and Mead and have at it)

For digital stuff, small boards with FPGAs or microcontrollers on them
are probably the sweet spot for small runs.

The same is not true for analog.



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John Allen
2015-08-10 02:57:19 UTC
Permalink
Hi Jim -

You wrote:
At some point, multiproject wafers (like MOSIS) might become a hobby
product. So far, it's in the "several kilobuck" minimum purchase, and,
as well, the tools aren't easy to come by. Or, more properly, good
design tools are expensive, tedious design tools are free.. you CAN
layout an IC for MOSIS with a ruler and and a quadrille pad.. get your
copy of Carver and Mead and have at it)

I assume that you mean Carver Mead and Lynn Conway, Introduction to VLSI System Design 1978.

I am enjoying this thread!

Regards, John Allen K1AE

-----Original Message-----
From: time-nuts [mailto:time-nuts-***@febo.com] On Behalf Of Jim Lux
Sent: Sunday, August 09, 2015 9:12 PM
To: time-***@febo.com
Subject: Re: [time-nuts] wtd: WWVB info
Post by Bob Camp
Hi
If you never have tried to keep an IC in production, there are some basic things
<snip>
There's always Rochester Electronics.. "leaders in the trailing edge"
(no kidding, that's their slogan)..

They buy old fabs, masks, etc, and keep producing small runs of older
parts. For a price.

At some point, multiproject wafers (like MOSIS) might become a hobby
product. So far, it's in the "several kilobuck" minimum purchase, and,
as well, the tools aren't easy to come by. Or, more properly, good
design tools are expensive, tedious design tools are free.. you CAN
layout an IC for MOSIS with a ruler and and a quadrille pad.. get your
copy of Carver and Mead and have at it)

For digital stuff, small boards with FPGAs or microcontrollers on them
are probably the sweet spot for small runs.

The same is not true for analog.



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Jim Lux
2015-08-10 03:54:01 UTC
Permalink
Post by John Allen
Hi Jim -
At some point, multiproject wafers (like MOSIS) might become a hobby
product. So far, it's in the "several kilobuck" minimum purchase, and,
as well, the tools aren't easy to come by. Or, more properly, good
design tools are expensive, tedious design tools are free.. you CAN
layout an IC for MOSIS with a ruler and and a quadrille pad.. get your
copy of Carver and Mead and have at it)
I assume that you mean Carver Mead and Lynn Conway, Introduction to VLSI System Design 1978.
Yup, Mead and Conway.. I misspoke/mistyped..
that's the one.


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Björn
2015-08-08 18:06:19 UTC
Permalink
Don't know about DE to USA shipping, but the bare modules are available for around or sub 10€ depending on quantity.

http://www.hkw-shop.de/Empfangstechnik-AM/Empfangs-Module/

/Björn
Post by Brian Inglis
Given a $10 60kHz receiver,
This is the problem.

I can not find $10 receivers any more.

I can find $15-$20 receivers (from the UK), add shipping and it minimum
$20+.

Even the older chips still work with the new format, its just finding
them, cheaply.

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Hal Murray
2015-08-10 05:07:24 UTC
Permalink
A few years ago I had been building some LED clocks for friends, more art
then electronics.
...
People keep saying there are WWVB chips available, but I can not find any
chips.
If you are using LEDs (rather than LCD), I assume you are not running off
batteries.

You might look into GPS devices. They aren't quite as cheap as the WWVB
chips, but there are lots of them on the market.
--
These are my opinions. I hate spam.



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Chris Albertson
2015-08-11 07:14:43 UTC
Permalink
You might look into GPS devices. They aren't quite as cheap as the WWVB
Post by Hal Murray
chips, but there are lots of them on the market.
Yes GPS receivers can be very cheap and self contained and much easier yo
use than those WWVB chips. I have two of the chips. I don't think they
work now that WWVB has changed format and even back in the day they only
worked for a few hours at night. GPS is better.

But there is another good source for correct time. Most people today have
WiFi in their house, at school and at work. If the clock is going into an
area where WiFi is available then it can connect to NTP. If the clock
connects to WiFi you can save money and parts count by not needing any
physical controls on the clock for setting or to control options as all
that can be done from a smart phone's web browser
--
Chris Albertson
Redondo Beach, California
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Adrian Godwin
2015-08-11 10:29:06 UTC
Permalink
The difficult thing about that is that making the wifi connection without
any user interface is difficult now that most wifi connections have
security enabled.
Post by Hal Murray
You might look into GPS devices. They aren't quite as cheap as the WWVB
Post by Hal Murray
chips, but there are lots of them on the market.
Yes GPS receivers can be very cheap and self contained and much easier yo
use than those WWVB chips. I have two of the chips. I don't think they
work now that WWVB has changed format and even back in the day they only
worked for a few hours at night. GPS is better.
But there is another good source for correct time. Most people today have
WiFi in their house, at school and at work. If the clock is going into an
area where WiFi is available then it can connect to NTP. If the clock
connects to WiFi you can save money and parts count by not needing any
physical controls on the clock for setting or to control options as all
that can be done from a smart phone's web browser
--
Chris Albertson
Redondo Beach, California
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