Discussion:
New WWVB format...
(too old to reply)
Burt I. Weiner
2012-09-26 15:49:25 UTC
Permalink
I'm sure most of this group has seen the information put out by NIST
regarding the changes to the WWVB format. But, for those who may not
yet have seen this, here's a link to it:

http://f1.grp.yahoofs.com/v1/cBhjUH41xVccWM9P8EU4JqzmFNevFgDUFkRcgfLyry1Rn3HqMV5iDqYDgsd2pM1-Vq3nhF9WERTjVF_WmRjAezjU9CCrAda_8RqV/NIST-Enhanced-WWVB-Broadcast-Format.pdf

The results of this change will apparently no longer allow WWVB to be
used as a high accuracy frequency standard signal. This does not
seem to be much of an issue considering the availability of the GPS
signals all over the world.

I use GPS as my frequency reference for my "Off-Air" broadcast
frequency measurement service. Some broadcast stations also use GPS
as a reference for their transmitters. I'm sometimes asked why I use
GPS as a reference when it is not recognized by NIST as the U.S.
Frequency Standard? Other than explaining the capabilities of GPS as
a reference, I don't have a real answer for their specific
question. I have publications from NIST showing the accuracies
obtainable using GPS, but it still does not appear to be an
"Official" U.S. Frequency Standard. So, I guess my question is, when
will NIST officially recognize GPS as, at least an alternate, U.S.
Frequency Standard? Have I missed something?

Thanks,

Burt, K6OQK

Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California U.S.A.
biwa-***@public.gmane.org
www.biwa.cc
K6OQK
Tom Miller
2012-09-26 16:46:27 UTC
Permalink
See:

http://www.nist.gov/calibrations/upload/1424.pdf

Re. GPS traceable to NIST.


----- Original Message -----
From: "Burt I. Weiner" <biwa-***@public.gmane.org>
To: <time-nuts-***@public.gmane.org>
Sent: Wednesday, September 26, 2012 11:49 AM
Subject: [time-nuts] New WWVB format...


I'm sure most of this group has seen the information put out by NIST
regarding the changes to the WWVB format. But, for those who may not
yet have seen this, here's a link to it:

http://f1.grp.yahoofs.com/v1/cBhjUH41xVccWM9P8EU4JqzmFNevFgDUFkRcgfLyry1Rn3HqMV5iDqYDgsd2pM1-Vq3nhF9WERTjVF_WmRjAezjU9CCrAda_8RqV/NIST-Enhanced-WWVB-Broadcast-Format.pdf

The results of this change will apparently no longer allow WWVB to be
used as a high accuracy frequency standard signal. This does not
seem to be much of an issue considering the availability of the GPS
signals all over the world.

I use GPS as my frequency reference for my "Off-Air" broadcast
frequency measurement service. Some broadcast stations also use GPS
as a reference for their transmitters. I'm sometimes asked why I use
GPS as a reference when it is not recognized by NIST as the U.S.
Frequency Standard? Other than explaining the capabilities of GPS as
a reference, I don't have a real answer for their specific
question. I have publications from NIST showing the accuracies
obtainable using GPS, but it still does not appear to be an
"Official" U.S. Frequency Standard. So, I guess my question is, when
will NIST officially recognize GPS as, at least an alternate, U.S.
Frequency Standard? Have I missed something?

Thanks,

Burt, K6OQK

Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California U.S.A.
biwa-***@public.gmane.org
www.biwa.cc
K6OQK


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Bob Camp
2012-09-26 16:54:29 UTC
Permalink
Hi

At least from here, that link appears to be broken. If it's the same details
as on the NIST web site, they are already part of a thread here.

Bob

-----Original Message-----
From: time-nuts-bounces-***@public.gmane.org [mailto:time-nuts-bounces-***@public.gmane.org] On
Behalf Of Burt I. Weiner
Sent: Wednesday, September 26, 2012 11:49 AM
To: time-nuts-***@public.gmane.org
Subject: [time-nuts] New WWVB format...

I'm sure most of this group has seen the information put out by NIST
regarding the changes to the WWVB format. But, for those who may not
yet have seen this, here's a link to it:

http://f1.grp.yahoofs.com/v1/cBhjUH41xVccWM9P8EU4JqzmFNevFgDUFkRcgfLyry1Rn3H
qMV5iDqYDgsd2pM1-Vq3nhF9WERTjVF_WmRjAezjU9CCrAda_8RqV/NIST-Enhanced-WWVB-Bro
adcast-Format.pdf

The results of this change will apparently no longer allow WWVB to be
used as a high accuracy frequency standard signal. This does not
seem to be much of an issue considering the availability of the GPS
signals all over the world.

I use GPS as my frequency reference for my "Off-Air" broadcast
frequency measurement service. Some broadcast stations also use GPS
as a reference for their transmitters. I'm sometimes asked why I use
GPS as a reference when it is not recognized by NIST as the U.S.
Frequency Standard? Other than explaining the capabilities of GPS as
a reference, I don't have a real answer for their specific
question. I have publications from NIST showing the accuracies
obtainable using GPS, but it still does not appear to be an
"Official" U.S. Frequency Standard. So, I guess my question is, when
will NIST officially recognize GPS as, at least an alternate, U.S.
Frequency Standard? Have I missed something?

Thanks,

Burt, K6OQK

Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California U.S.A.
biwa-***@public.gmane.org
www.biwa.cc
K6OQK


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Tom Van Baak
2012-09-26 17:13:22 UTC
Permalink
For those of you who don't dare click on encrypted Yahoo URL's, the original NIST link is:

http://www.nist.gov/pml/div688/grp40/upload/NIST-Enhanced-WWVB-Broadcast-Format-sept-2012-Radio-Station-staff.pdf

Burt,

My reading of the document(s) is that the new format will in fact allow WWVB to be used as a frequency standard with even greater precision then before, though not with unmodified legacy WWVB carrier receivers. My hope is that one of you will produce a clever reference design for such a T&F receiver make it available to the group. It sounds like a very fun DSP project; one that we can all learn from. Bonus points for making it an open-source Arduino shield. Making it work with both DCF77 and WWVB would also be a plus.

If nothing else, a well-documented hack for existing Spectracom and HP WWVB receivers would be welcome. A third idea is a translator that receives the new carrier format and re-transmits the old carrier format; that way no mods need to be made to legacy WWVB receivers at all, regardless of age. It would be similar to the way the G2G (GPS to GOES) translator worked. Extra credit for adding back the 45 degree hourly phase shift.

/tvb

----- Original Message -----
From: "Burt I. Weiner" <biwa-***@public.gmane.org>
To: <time-nuts-***@public.gmane.org>
Sent: Wednesday, September 26, 2012 8:49 AM
Subject: [time-nuts] New WWVB format...
Post by Burt I. Weiner
I'm sure most of this group has seen the information put out by NIST
regarding the changes to the WWVB format. But, for those who may not
http://f1.grp.yahoofs.com/v1/cBhjUH41xVccWM9P8EU4JqzmFNevFgDUFkRcgfLyry1Rn3HqMV5iDqYDgsd2pM1-Vq3nhF9WERTjVF_WmRjAezjU9CCrAda_8RqV/NIST-Enhanced-WWVB-Broadcast-Format.pdf
The results of this change will apparently no longer allow WWVB to be
used as a high accuracy frequency standard signal. This does not
seem to be much of an issue considering the availability of the GPS
signals all over the world.
I use GPS as my frequency reference for my "Off-Air" broadcast
frequency measurement service. Some broadcast stations also use GPS
as a reference for their transmitters. I'm sometimes asked why I use
GPS as a reference when it is not recognized by NIST as the U.S.
Frequency Standard? Other than explaining the capabilities of GPS as
a reference, I don't have a real answer for their specific
question. I have publications from NIST showing the accuracies
obtainable using GPS, but it still does not appear to be an
"Official" U.S. Frequency Standard. So, I guess my question is, when
will NIST officially recognize GPS as, at least an alternate, U.S.
Frequency Standard? Have I missed something?
Thanks,
Burt, K6OQK
Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California U.S.A.
www.biwa.cc
K6OQK
paul swed
2012-09-26 17:32:55 UTC
Permalink
I may have at least the spectracoms figured out. Its a hack and at least
using my homebrew wwvb psk encoder seems to work. But its not a general
purpose design. It will work with the fluke 207 and HP 117s but you have to
have a base spectracom to hack.
Technically speaking unattractive.
But that said I am waiting for the real wwvb to send bpsk again to claim
any victory. Its a real challenge on the east coast as compared to folks in
the mid and central west areas that have produced answers...
I will also say that over the last 6 months. John and I have hacked a lot
of the "solutions". They do not fare well.
Regards
Paul
WB8TSL/1
Post by Tom Van Baak
http://www.nist.gov/pml/div688/grp40/upload/NIST-Enhanced-WWVB-Broadcast-Format-sept-2012-Radio-Station-staff.pdf
Burt,
My reading of the document(s) is that the new format will in fact allow
WWVB to be used as a frequency standard with even greater precision then
before, though not with unmodified legacy WWVB carrier receivers. My hope
is that one of you will produce a clever reference design for such a T&F
receiver make it available to the group. It sounds like a very fun DSP
project; one that we can all learn from. Bonus points for making it an
open-source Arduino shield. Making it work with both DCF77 and WWVB would
also be a plus.
If nothing else, a well-documented hack for existing Spectracom and HP
WWVB receivers would be welcome. A third idea is a translator that receives
the new carrier format and re-transmits the old carrier format; that way no
mods need to be made to legacy WWVB receivers at all, regardless of age. It
would be similar to the way the G2G (GPS to GOES) translator worked. Extra
credit for adding back the 45 degree hourly phase shift.
/tvb
----- Original Message -----
Sent: Wednesday, September 26, 2012 8:49 AM
Subject: [time-nuts] New WWVB format...
Post by Burt I. Weiner
I'm sure most of this group has seen the information put out by NIST
regarding the changes to the WWVB format. But, for those who may not
http://f1.grp.yahoofs.com/v1/cBhjUH41xVccWM9P8EU4JqzmFNevFgDUFkRcgfLyry1Rn3HqMV5iDqYDgsd2pM1-Vq3nhF9WERTjVF_WmRjAezjU9CCrAda_8RqV/NIST-Enhanced-WWVB-Broadcast-Format.pdf
Post by Burt I. Weiner
The results of this change will apparently no longer allow WWVB to be
used as a high accuracy frequency standard signal. This does not
seem to be much of an issue considering the availability of the GPS
signals all over the world.
I use GPS as my frequency reference for my "Off-Air" broadcast
frequency measurement service. Some broadcast stations also use GPS
as a reference for their transmitters. I'm sometimes asked why I use
GPS as a reference when it is not recognized by NIST as the U.S.
Frequency Standard? Other than explaining the capabilities of GPS as
a reference, I don't have a real answer for their specific
question. I have publications from NIST showing the accuracies
obtainable using GPS, but it still does not appear to be an
"Official" U.S. Frequency Standard. So, I guess my question is, when
will NIST officially recognize GPS as, at least an alternate, U.S.
Frequency Standard? Have I missed something?
Thanks,
Burt, K6OQK
Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California U.S.A.
www.biwa.cc
K6OQK
_______________________________________________
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
John Ackermann N8UR
2012-09-26 17:47:27 UTC
Permalink
Paul, I have a couple of Spectracoms running and have pretty decent WWVB
signal strength here. I'd be happy to test the hack.

John
----
Post by paul swed
I may have at least the spectracoms figured out. Its a hack and at least
using my homebrew wwvb psk encoder seems to work. But its not a general
purpose design. It will work with the fluke 207 and HP 117s but you have to
have a base spectracom to hack.
Technically speaking unattractive.
But that said I am waiting for the real wwvb to send bpsk again to claim
any victory. Its a real challenge on the east coast as compared to folks in
the mid and central west areas that have produced answers...
I will also say that over the last 6 months. John and I have hacked a lot
of the "solutions". They do not fare well.
Regards
Paul
WB8TSL/1
Post by Tom Van Baak
For those of you who don't dare click on encrypted Yahoo URL's, the
http://www.nist.gov/pml/div688/grp40/upload/NIST-Enhanced-WWVB-Broadcast-Format-sept-2012-Radio-Station-staff.pdf
Burt,
My reading of the document(s) is that the new format will in fact allow
WWVB to be used as a frequency standard with even greater precision then
before, though not with unmodified legacy WWVB carrier receivers. My hope
is that one of you will produce a clever reference design for such a T&F
receiver make it available to the group. It sounds like a very fun DSP
project; one that we can all learn from. Bonus points for making it an
open-source Arduino shield. Making it work with both DCF77 and WWVB would
also be a plus.
If nothing else, a well-documented hack for existing Spectracom and HP
WWVB receivers would be welcome. A third idea is a translator that receives
the new carrier format and re-transmits the old carrier format; that way no
mods need to be made to legacy WWVB receivers at all, regardless of age. It
would be similar to the way the G2G (GPS to GOES) translator worked. Extra
credit for adding back the 45 degree hourly phase shift.
/tvb
----- Original Message -----
Sent: Wednesday, September 26, 2012 8:49 AM
Subject: [time-nuts] New WWVB format...
Post by Burt I. Weiner
I'm sure most of this group has seen the information put out by NIST
regarding the changes to the WWVB format. But, for those who may not
http://f1.grp.yahoofs.com/v1/cBhjUH41xVccWM9P8EU4JqzmFNevFgDUFkRcgfLyry1Rn3HqMV5iDqYDgsd2pM1-Vq3nhF9WERTjVF_WmRjAezjU9CCrAda_8RqV/NIST-Enhanced-WWVB-Broadcast-Format.pdf
Post by Burt I. Weiner
The results of this change will apparently no longer allow WWVB to be
used as a high accuracy frequency standard signal. This does not
seem to be much of an issue considering the availability of the GPS
signals all over the world.
I use GPS as my frequency reference for my "Off-Air" broadcast
frequency measurement service. Some broadcast stations also use GPS
as a reference for their transmitters. I'm sometimes asked why I use
GPS as a reference when it is not recognized by NIST as the U.S.
Frequency Standard? Other than explaining the capabilities of GPS as
a reference, I don't have a real answer for their specific
question. I have publications from NIST showing the accuracies
obtainable using GPS, but it still does not appear to be an
"Official" U.S. Frequency Standard. So, I guess my question is, when
will NIST officially recognize GPS as, at least an alternate, U.S.
Frequency Standard? Have I missed something?
Thanks,
Burt, K6OQK
Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California U.S.A.
www.biwa.cc
K6OQK
_______________________________________________
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Majdi S. Abbas
2012-09-26 18:19:42 UTC
Permalink
Post by Tom Van Baak
My reading of the document(s) is that the new format will in fact allow
WWVB to be used as a frequency standard with even greater precision then
before, though not with unmodified legacy WWVB carrier receivers. My hope
is that one of you will produce a clever reference design for such a T&F
receiver make it available to the group. It sounds like a very fun DSP
project; one that we can all learn from. Bonus points for making it an
open-source Arduino shield. Making it work with both DCF77 and WWVB would
also be a plus.
DSP would be good, although I also think an microcontroller
implementation could be interesting. Atmel's ARM MCUs look like they'd
be good candidates for this sort of thing. (Pretty fast, enough storage
to do interesting things with it, and a fast enough ADC for 60 KHz.)

I've got a couple of these that I might use as a development
platform:

https://www.olimex.com/Products/ARM/Atmel/SAM7-P256/

Has anyone come up with a reasonable algorithm to implement in
a microcontroller? (DSP development kits are a bit more spendy than I'd
like to invest in a prototype. :)
Post by Tom Van Baak
If nothing else, a well-documented hack for existing Spectracom and HP
WWVB receivers would be welcome. A third idea is a translator that
receives the new carrier format and re-transmits the old carrier format;
that way no mods need to be made to legacy WWVB receivers at all,
regardless of age. It would be similar to the way the G2G (GPS to GOES)
translator worked. Extra credit for adding back the 45 degree hourly
phase shift.
I'm not sure I want the phase shift back. Some references
don't handle it gracefully.

That said, I have the following victims (time interval and TOD):
- TrueTime 60DC and 60LF
- Spectracom Netclock/2

As far as I'm concerned I'm willing to modify any of these at
this point. I've got a rough idea how to modify the 60DC: seems like
you could double the 60 KHz LO after the IRIG output divisor chain, as
it's headed into the PLL, and double the incoming signal after the RF
amp. This is convenient since it's running between assemblies, anyway.

Does anyone have a manual or schematic for the 60LF? I could
probably figure it out, but it'll be easier with documentation.

Thoughts on modifications are welcome, I'd even be happy to compile
them all into a public list somewhere.

--msa
Chris Albertson
2012-09-26 18:38:10 UTC
Permalink
Post by Majdi S. Abbas
DSP would be good, although I also think an microcontroller
implementation could be interesting. Atmel's ARM MCUs look like they'd
be good candidates for this sort of thing.
The first stepis to simply use a regular PC, maybe running Linux.
This is the easiest and fastest platform to develop on. It gets
harder and takes longer if you use a smaller and more esoteric
platform like a DSP or FPGA. Using a quad core Intel chip is gross
over kill but it allows for quick development. Later with working
software you have actually measurements in hand and can pick a "right
size" processor.

The wrong way to do it is to select hardware before you even have the
basic sketch of the software algorithm. The best way is "software
first". You don't even need an RF front and. You can simulate what
the D/A converter would see based on the transmitter spec and feed
that to your software before you even put up an antenna. I worked on
a project where we actually did that. We built a simulation of the
transmitter first. At first the sim was very crude and simple.
Later we added noise, multi path and so on. This allowed the radar
receivers to be tested without special hardware and most importantly
it allowed regression testing of the software after every upgrade.

If you need a stating point a time code generator that outputs the
"old" WWVB signal is available as part if the NTP source code
distribution in a /test directory. Is was written to help test NTP's
time code reference clock. NTP has a way to connect a time code that
is at baseband to audio "sound card" and use it as a reference. The
test software produced the "old format" baseband. I'm saying this
so that no one wastes time reinventing wheels.


Chris Albertson
Redondo Beach, California
Majdi S. Abbas
2012-09-26 18:59:33 UTC
Permalink
Post by Chris Albertson
The first stepis to simply use a regular PC, maybe running Linux.
This is the easiest and fastest platform to develop on. It gets
harder and takes longer if you use a smaller and more esoteric
platform like a DSP or FPGA. Using a quad core Intel chip is gross
over kill but it allows for quick development. Later with working
software you have actually measurements in hand and can pick a "right
size" processor.
Normally I'd agree with you but where 60 KHz signals are
concerned, I think I'd rather not use a PC. There's just too much RFI.
A microcontroller with a single clock at a much higher frequency is less
likely to interfere with itself. I'm not worried about exactly sizing
this, anything we're likely to use is more than fast enough to handle
this coding at such a low frequency.
Post by Chris Albertson
If you need a stating point a time code generator that outputs the
"old" WWVB signal is available as part if the NTP source code
distribution in a /test directory. Is was written to help test NTP's
time code reference clock. NTP has a way to connect a time code that
is at baseband to audio "sound card" and use it as a reference. The
test software produced the "old format" baseband. I'm saying this
so that no one wastes time reinventing wheels.
I'm aware of the 'tg' program in the util directory, but that is
for WWV or IRIG audio. To my knowledge, there are no extant simulators
out there for WWVB.

Do you know otherwise?

--msa
Chris Albertson
2012-09-26 19:57:43 UTC
Permalink
Post by Majdi S. Abbas
Post by Chris Albertson
The first stepis to simply use a regular PC, maybe running Linux.
This is the easiest and fastest platform to develop on. It gets
harder and takes longer if you use a smaller and more esoteric
platform like a DSP or FPGA. Using a quad core Intel chip is gross
over kill but it allows for quick development. Later with working
software you have actually measurements in hand and can pick a "right
size" processor.
Normally I'd agree with you but where 60 KHz signals are
concerned, I think I'd rather not use a PC. There's just too much RFI.
If I do this the PC would likely be a good large distance from the RF
front end. With an SDR type receiver you'd place the RF stuff very
close to the antenna and the long cable from RF section to computer is
a balanced audio cable, like an XLR microphone cable. By current
60MHZ WWVB receiver lives outdoors inside a 1 foot length of PVC pipe
far from the house. Only serial data leaves the pipe and DC power
goes in.

Also the RFI from a PC depends on who built it. Typical
self-assembled computers are very poor. Notebooks can be good. bUt
thebest plan is to use the inverse square law and some distance and
RFI goes away.


Chris Albertson
Redondo Beach, California
Don Latham
2012-09-26 18:59:55 UTC
Permalink
This is a job for Raspberry Pi...
Don

Majdi S. Abbas
Post by Majdi S. Abbas
Post by Tom Van Baak
My reading of the document(s) is that the new format will in fact allow
WWVB to be used as a frequency standard with even greater precision then
before, though not with unmodified legacy WWVB carrier receivers. My hope
is that one of you will produce a clever reference design for such a T&F
receiver make it available to the group. It sounds like a very fun DSP
project; one that we can all learn from. Bonus points for making it an
open-source Arduino shield. Making it work with both DCF77 and WWVB would
also be a plus.
DSP would be good, although I also think an microcontroller
implementation could be interesting. Atmel's ARM MCUs look like they'd
be good candidates for this sort of thing. (Pretty fast, enough storage
to do interesting things with it, and a fast enough ADC for 60 KHz.)
I've got a couple of these that I might use as a development
https://www.olimex.com/Products/ARM/Atmel/SAM7-P256/
Has anyone come up with a reasonable algorithm to implement in
a microcontroller? (DSP development kits are a bit more spendy than I'd
like to invest in a prototype. :)
Post by Tom Van Baak
If nothing else, a well-documented hack for existing Spectracom and HP
WWVB receivers would be welcome. A third idea is a translator that
receives the new carrier format and re-transmits the old carrier format;
that way no mods need to be made to legacy WWVB receivers at all,
regardless of age. It would be similar to the way the G2G (GPS to GOES)
translator worked. Extra credit for adding back the 45 degree hourly
phase shift.
I'm not sure I want the phase shift back. Some references
don't handle it gracefully.
- TrueTime 60DC and 60LF
- Spectracom Netclock/2
As far as I'm concerned I'm willing to modify any of these at
this point. I've got a rough idea how to modify the 60DC: seems like
you could double the 60 KHz LO after the IRIG output divisor chain, as
it's headed into the PLL, and double the incoming signal after the RF
amp. This is convenient since it's running between assemblies, anyway.
Does anyone have a manual or schematic for the 60LF? I could
probably figure it out, but it'll be easier with documentation.
Thoughts on modifications are welcome, I'd even be happy to compile
them all into a public list somewhere.
--msa
_______________________________________________
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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--
"Neither the voice of authority nor the weight of reason and argument
are as significant as experiment, for thence comes quiet to the mind."
De Erroribus Medicorum, R. Bacon, 13th century.
"If you don't know what it is, don't poke it."
Ghost in the Shell


Dr. Don Latham AJ7LL
Six Mile Systems LLP
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
www.lightningforensics.com
www.sixmilesystems.com
Dennis Ferguson
2012-09-26 21:36:09 UTC
Permalink
Post by Majdi S. Abbas
Post by Tom Van Baak
My reading of the document(s) is that the new format will in fact allow
WWVB to be used as a frequency standard with even greater precision then
before, though not with unmodified legacy WWVB carrier receivers. My hope
is that one of you will produce a clever reference design for such a T&F
receiver make it available to the group. It sounds like a very fun DSP
project; one that we can all learn from. Bonus points for making it an
open-source Arduino shield. Making it work with both DCF77 and WWVB would
also be a plus.
DSP would be good, although I also think an microcontroller
implementation could be interesting. Atmel's ARM MCUs look like they'd
be good candidates for this sort of thing. (Pretty fast, enough storage
to do interesting things with it, and a fast enough ADC for 60 KHz.)
This is fine, though to make it maximally useful for time and
frequency purposes I believe the hardware might need to provide a
way to synchronize the ADC clock to an external reference, and likely
some way to time-mark the incoming data (e.g. a quick-and-dirty version
might feed a PPS signal to the second channel of a stereo ADC, if no
more elegant solution is available). A control loop to discipline an
oscillator's output might use that oscillator to clock the ADC and adjust
the oscillator to zero the ADC's phase alignment with the input signal,
if that can be made to work. A system to measure WWVB propagation delays and
signal levels might instead clock the ADC and the time marker with a
known-accurate frequency and PPS (e.g. a GPSDO).

RFSpace makes commercial LF/MF/HF SDR equipment with almost the right inputs
for this (an external frequency input and a timing trigger). What I'd like
is a tiny-budget version of this just for LF stations.
Post by Majdi S. Abbas
I've got a couple of these that I might use as a development
https://www.olimex.com/Products/ARM/Atmel/SAM7-P256/
Has anyone come up with a reasonable algorithm to implement in
a microcontroller? (DSP development kits are a bit more spendy than I'd
like to invest in a prototype. :)
I guess the trouble with this is only that the availability of brute force
can sometimes make it unnecessary to deal with a lot of complexity. If your
job is to do a convolution of a model of what you know was transmitted
against the incoming signal to measure the time alignment then using a
platform where you can store big blocks of data and do Fourier transforms
with wild abandon can provide really good results without having to spend
a lot of time thinking about it. Even quite modest modern PC hardware comes
with a boatload of memory and is exceedingly speedy, and for some purposes
it can save a lot of time and effort just to make use of that compared to
trying to do without.

I have a quick-hack DCF77 PM detector which runs on PC hardware and makes use
of one of the above-mentioned RFSpace receivers for the data acquisition. While
it is now in boxes being moved, when I get it back up I would love to lose the
RFSpace receiver in favor of something much less costly, but would hate trying
to make this work with something less capable than the PC. Using a microcontroller
like that to do the A/D conversions and send the data collected out (say) an
ethernet port to a PC which does the heavy computational lifting (that's what the
RFSpace receiver does) would appeal to me, but trying to do without the PC would
not.

Dennis Ferguson
paul swed
2012-09-26 21:43:49 UTC
Permalink
Might be a bit of a cost. The SDR runs $1495.
Regards
Paul

On Wed, Sep 26, 2012 at 5:36 PM, Dennis Ferguson <
Post by Dennis Ferguson
Post by Majdi S. Abbas
Post by Tom Van Baak
My reading of the document(s) is that the new format will in fact allow
WWVB to be used as a frequency standard with even greater precision then
before, though not with unmodified legacy WWVB carrier receivers. My
hope
Post by Majdi S. Abbas
Post by Tom Van Baak
is that one of you will produce a clever reference design for such a T&F
receiver make it available to the group. It sounds like a very fun DSP
project; one that we can all learn from. Bonus points for making it an
open-source Arduino shield. Making it work with both DCF77 and WWVB
would
Post by Majdi S. Abbas
Post by Tom Van Baak
also be a plus.
DSP would be good, although I also think an microcontroller
implementation could be interesting. Atmel's ARM MCUs look like they'd
be good candidates for this sort of thing. (Pretty fast, enough storage
to do interesting things with it, and a fast enough ADC for 60 KHz.)
This is fine, though to make it maximally useful for time and
frequency purposes I believe the hardware might need to provide a
way to synchronize the ADC clock to an external reference, and likely
some way to time-mark the incoming data (e.g. a quick-and-dirty version
might feed a PPS signal to the second channel of a stereo ADC, if no
more elegant solution is available). A control loop to discipline an
oscillator's output might use that oscillator to clock the ADC and adjust
the oscillator to zero the ADC's phase alignment with the input signal,
if that can be made to work. A system to measure WWVB propagation delays and
signal levels might instead clock the ADC and the time marker with a
known-accurate frequency and PPS (e.g. a GPSDO).
RFSpace makes commercial LF/MF/HF SDR equipment with almost the right inputs
for this (an external frequency input and a timing trigger). What I'd like
is a tiny-budget version of this just for LF stations.
Post by Majdi S. Abbas
I've got a couple of these that I might use as a development
https://www.olimex.com/Products/ARM/Atmel/SAM7-P256/
Has anyone come up with a reasonable algorithm to implement in
a microcontroller? (DSP development kits are a bit more spendy than I'd
like to invest in a prototype. :)
I guess the trouble with this is only that the availability of brute force
can sometimes make it unnecessary to deal with a lot of complexity. If your
job is to do a convolution of a model of what you know was transmitted
against the incoming signal to measure the time alignment then using a
platform where you can store big blocks of data and do Fourier transforms
with wild abandon can provide really good results without having to spend
a lot of time thinking about it. Even quite modest modern PC hardware comes
with a boatload of memory and is exceedingly speedy, and for some purposes
it can save a lot of time and effort just to make use of that compared to
trying to do without.
I have a quick-hack DCF77 PM detector which runs on PC hardware and makes use
of one of the above-mentioned RFSpace receivers for the data acquisition.
While
it is now in boxes being moved, when I get it back up I would love to lose the
RFSpace receiver in favor of something much less costly, but would hate trying
to make this work with something less capable than the PC. Using a microcontroller
like that to do the A/D conversions and send the data collected out (say) an
ethernet port to a PC which does the heavy computational lifting (that's what the
RFSpace receiver does) would appeal to me, but trying to do without the PC would
not.
Dennis Ferguson
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To unsubscribe, go to
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and follow the instructions there.
Dennis Ferguson
2012-09-26 21:53:51 UTC
Permalink
Post by paul swed
Might be a bit of a cost. The SDR runs $1495.
Regards
Paul
The ones with the clock input options (the SDR-IP
and the NetSDR, I think) are significantly more than
that. But they are also huge overkill if all you want is
a digital LF receiver.

That's why I'd like to replace it with something cheap,
but that something wouldn't be nearly as useful without
the clock and timing edge inputs.

Dennis Ferguson
paul swed
2012-09-26 22:35:00 UTC
Permalink
Hmmm SDR. Does that mean spensive darn radio?
Joking aside its clearly massive overkill.
The rf front end is very reasonable and 3-4 stages of opamps like the TL08X
class will do a very fine job and you can even use stages as active
bandpass filters etc. Have built a few over the last 6 months. Its the
various other things that get messy. Compression to deal with the amplitude
modulation, agc etc. Forget hard limiting what a mess that made. Then after
you have that settled you can jump into the technology of your interest.
I will say that there are lots of high level concepts but the devil is in
the detail.
What is clear is that the system has to know whats going on in the channel.
Impulse noise and fades here on the east coast make the design difficult.
As compared to say a Kansas station in the 500 uv signal region. The weak
signal and channel behaviors tend to make lots of great ideas useless.
I did also tinker with spectrum lab and a pc. Looked interesting and maybe
could have value.
But running a PC 24X7 seems like a Kluge. I prefer low power solutions
measured in sub 100 ma. Hey its got to be green because wwvb really isn't.
Regards
Paul
WB8TSL

On Wed, Sep 26, 2012 at 5:53 PM, Dennis Ferguson <
Post by Dennis Ferguson
Post by paul swed
Might be a bit of a cost. The SDR runs $1495.
Regards
Paul
The ones with the clock input options (the SDR-IP
and the NetSDR, I think) are significantly more than
that. But they are also huge overkill if all you want is
a digital LF receiver.
That's why I'd like to replace it with something cheap,
but that something wouldn't be nearly as useful without
the clock and timing edge inputs.
Dennis Ferguson
_______________________________________________
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Magnus Danielson
2012-09-27 00:19:32 UTC
Permalink
Post by Tom Van Baak
http://www.nist.gov/pml/div688/grp40/upload/NIST-Enhanced-WWVB-Broadcast-Format-sept-2012-Radio-Station-staff.pdf
Burt,
My reading of the document(s) is that the new format will in fact allow WWVB to be used as a frequency standard with even greater precision then before, though not with unmodified legacy WWVB carrier receivers. My hope is that one of you will produce a clever reference design for such a T&F receiver make it available to the group. It sounds like a very fun DSP project; one that we can all learn from. Bonus points for making it an open-source Arduino shield. Making it work with both DCF77 and WWVB would also be a plus.
If nothing else, a well-documented hack for existing Spectracom and HP WWVB receivers would be welcome. A third idea is a translator that receives the new carrier format and re-transmits the old carrier format; that way no mods need to be made to legacy WWVB receivers at all, regardless of age. It would be similar to the way the G2G (GPS to GOES) translator worked. Extra credit for adding back the 45 degree hourly phase shift.
Looking at it, the BPSK receiver strategy often becomes the Costas loop
should maybe not be that much of a modification to some of these. The AM
and PM modulation should be fairly trivial to crank out of them.

In a Costas loop, you mix-down your input signal in both I and Q signal,
by using both the cos and sin variant of an oscillator, which can be
realized by several means. The I and Q mixer outputs is then low-pass
filtered. The I and Q is mixed to provide the phase detector signal,
which is then used for the normal PLL loop.

Modifing a standard loop into a Costas loop involves adding a 0-90 phase
splitter (see polyphase filters), a pair of mixers and a pair of
low-pass filters. If the oscillator is available at 4 times the target
rate, a cheap digital trick can be used to create an oscillator
phase-split by xoring the bits or using other alternating methods. The
Tayloe detector might be a thing to look at in that case.

The Costas loop is a good vehicle towards a MAP receiver if you as so
inclined.

There was a paper on the new signal, and some receiver strategies.

Another trick to remember is that both the AM and PM signal has a very
high degree of predictability as many bits re-occur precisely or can be
predicted out of earlier state. The redundancy bits provide redundancy
within each frame rather than between frames. Thus, the actual
information flow or "news" in the channel is essentially zero once you
have locked into the signal. What changes is your oscillators phase, and
the amplitude and phase of the transmission-path.

I'm not near the WWVB transmitter to care enough to rebuild a receiver,
but I would guess that the handy time-nuts would not have too hard to
hack their existing receivers into a Costas setup.

Cheers,
Magnus

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