Test WWV timecube against Cesium, Rubidium, MASER or other precision time (UT-1) metrology
Hello Friends,
I am picking up locally a couple of vintage analog Radio Shack SW time cube
radios, 70s vintage, 3 switchable SW frequencies. Two types, the one
pictured and a Radio Shack model also that has WWV and Weather channel VHF
frequencies.
I am interested in an accurate bench test to compare the analog shortwave
radios time reporting
hopefully UT-1 against other available references. For accuracy, and
repeatability. Could eventually add an SDR to the mix, too.
The 5,10,15 mhz radios obviously are subject to the WWV Ft Collins site,
propagation distance delays, somewhat calculable, and the vagaries of
Ionospheric propagation, and, propagation delays between the antenna and
the measured tap point to the seconds ticks of WWV. I have some friends,
microwave professionals, who are also hams here in Auburn who may enjoy
doing a bench test, with published results, etc. But wonder if anyone else
would be interested in borrowing a RS Timecube radio (and/or use an SDR)
and designing an accurate bench test against available modern standards?
We are talking probably HUGE UT-1 errors compared to what this group plays
with, and that is OK but I think still a worthwhile test, especially if the
errors using available and cheap equipment are predictable, and repeatable.
https://forums.qrz.com/index.php?attachments/dscn1187-jpg.400844/
Another question: Re precision frequency measurements of spacecraft
carriers at earth ground stations. I have found a number of MASER labs,
willing to help measure a 70 cm UHF carrier of a satellite planned mission,
circling the moon. Fun, and overkill yes . But I would like to know if
the MASER extra 3 orders of magnitude precision frequency measurement (over
Rubidium, Cesium) is useful, or utterly wasted in measuring a lunar
orbiting spacecraft frequency over as long a period as a month, in a coming
satellite mission? Or, are Rubidium and Cesium and GPS disciplined
references plenty accurate for accurate spacecraft orbit determinations?
Best, 73, Pat Barthelow AA6EG
apol apolloeme@gmail.comloeme@gmail.com
"The most exciting phrase to hear in Science, the one that heraldsnew
discoveries, is not "Eureka, I have found it!" but:
"That's funny..." ----Isaac Asimov
Pat
Way back in the 90s I measured the color subcarrier frequency of
geostationary satellites. That aren't actually stationary.
I knew the quality of the subcarriers for a number of the networks since we
originated the signals. CBS was Cs others were Rb and still others various
Xtals. I had direct access to the references.
I used an HP5360 and homebrew interface collecting the data on a computer.
I was using a wide variety back then.
No matter. I actually could see over long periods the orbital day to day
and seasonal behaviors. By gosh physics and such in action. The reference
was the 5360s oven oscillator that was quite good. I know times have
changed. The reason to do it was simply because I could.
All of that said I will believe the doppler shifts are your biggest impact
so not sure orders of magnitude really help and may actually confuse. You
will have the effects of earth, the moon and the satellites orbit. Now
thats some serious math and thinking. Some place along the line other great
stuff will work to mess with you.
Regards
Paul
WB8TSL
On Thu, Dec 7, 2017 at 8:48 AM, Patrick Barthelow apolloeme@gmail.com
wrote:
Hello Friends,
I am picking up locally a couple of vintage analog Radio Shack SW time cube
radios, 70s vintage, 3 switchable SW frequencies. Two types, the one
pictured and a Radio Shack model also that has WWV and Weather channel VHF
frequencies.
I am interested in an accurate bench test to compare the analog shortwave
radios time reporting
hopefully UT-1 against other available references. For accuracy, and
repeatability. Could eventually add an SDR to the mix, too.
The 5,10,15 mhz radios obviously are subject to the WWV Ft Collins site,
propagation distance delays, somewhat calculable, and the vagaries of
Ionospheric propagation, and, propagation delays between the antenna and
the measured tap point to the seconds ticks of WWV. I have some friends,
microwave professionals, who are also hams here in Auburn who may enjoy
doing a bench test, with published results, etc. But wonder if anyone else
would be interested in borrowing a RS Timecube radio (and/or use an SDR)
and designing an accurate bench test against available modern standards?
We are talking probably HUGE UT-1 errors compared to what this group plays
with, and that is OK but I think still a worthwhile test, especially if the
errors using available and cheap equipment are predictable, and repeatable.
https://forums.qrz.com/index.php?attachments/dscn1187-jpg.400844/
Another question: Re precision frequency measurements of spacecraft
carriers at earth ground stations. I have found a number of MASER labs,
willing to help measure a 70 cm UHF carrier of a satellite planned mission,
circling the moon. Fun, and overkill yes . But I would like to know if
the MASER extra 3 orders of magnitude precision frequency measurement (over
Rubidium, Cesium) is useful, or utterly wasted in measuring a lunar
orbiting spacecraft frequency over as long a period as a month, in a coming
satellite mission? Or, are Rubidium and Cesium and GPS disciplined
references plenty accurate for accurate spacecraft orbit determinations?
Best, 73, Pat Barthelow AA6EG
apol apolloeme@gmail.comloeme@gmail.com
"The most exciting phrase to hear in Science, the one that heraldsnew
discoveries, is not "Eureka, I have found it!" but:
"That's funny..." ----Isaac Asimov
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
One way to compare any WWV receiver to a local standard is to use the
PPS output of a standard against the PPS tick modulated on WWV. The tick
is five cycles of a one KHz signal derived from the master frequency.
See
https://www.nist.gov/pml/time-and-frequency-division/time-services/wwv-a
nd-wwvh-digital-time-code-and-broadcast-format
It will be a bit tricky to determine the onset of the first cycle amid
the noise on shortwave radio. A computation that determined that there
were just 5 cycles and worked backwards to determine the timestamp of
the beginning or middle of the tick could then allow calculation of the
offset between the standard PPS and the tick. Limit of accuracy might be
100 microseconds.
Years ago, I had a standard calibrator made by Lavoie that had a vacuum
tube WWV receiver. IIRC, the WWV carrier caused a circular sweep on a 2
inch CRT. The sine wave from a standard modulated the intensity of the
circular trace, so that a bright half moon appeared on the CRT and
rotated at the error rate between the two frequencies. On several
evenings the dominant signal varied between WWV and WWVH (identified by
the voice broadcasts). Here in Minneapolis the phase difference between
the two stations was about 180 degrees, causing the bright arc on the
CRT to change sides.
So yes, this could be interesting for a hobbyist, but it won't add
anything to Science.
A MASER is overkill. Heck, so are Rubidium and Caesium.
A naked crystal will be rock solid compared to received WWV.
OTOH, NTP has marvelous mathematical tricks to reduce Internet
propagation delay.
A scheme to reduce varying atmospheric delay would be useful, if there
weren't much better ways to get a standard frequency.
Bill Hawkins
-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces@febo.com] On Behalf Of Patrick
Barthelow
Sent: Thursday, December 07, 2017 7:48 AM
Hello Friends,
I am picking up locally a couple of vintage analog Radio Shack SW time
cube radios, 70s vintage, 3 switchable SW frequencies. Two types, the
one pictured and a Radio Shack model also that has WWV and Weather
channel VHF frequencies.
I am interested in an accurate bench test to compare the analog
shortwave radios time reporting hopefully UT-1 against other available
references. For accuracy, and
repeatability. Could eventually add an SDR to the mix, too.
The 5,10,15 mhz radios obviously are subject to the WWV Ft Collins site,
propagation distance delays, somewhat calculable, and the vagaries of
Ionospheric propagation, and, propagation delays between the antenna and
the measured tap point to the seconds ticks of WWV. I have some
friends,
microwave professionals, who are also hams here in Auburn who may enjoy
doing a bench test, with published results, etc. But wonder if anyone
else would be interested in borrowing a RS Timecube radio (and/or use an
SDR) and designing an accurate bench test against available modern
standards?
We are talking probably HUGE UT-1 errors compared to what this group
plays with, and that is OK but I think still a worthwhile test,
especially if the errors using available and cheap equipment are
predictable, and repeatable.
https://forums.qrz.com/index.php?attachments/dscn1187-jpg.400844/
----- %< ----- [snip of microwave stuff]
Best, 73, Pat Barthelow AA6EG
apol apolloeme@gmail.comloeme@gmail.com
Hi
If you happen to pick 5 or 10 MHz as your target frequency, all sorts of interesting
things come into play. The first is that any 5 or 10 MHz local standard distribution
may well get into your receiver. That can create all sorts of odd effects as the signal
fades. Next is that you aren’t just on a channel for two stations. There are a number of
standard broadcasts that pop up. Depending on propagation, they may be strong
enough to notice.
If you can get WWV to give you sub 1 ms timing accuracy (or even low ms), that’s better
accuracy (as opposed to jitter) than NTP can do with a normal home internet connection.
Internet modems have some pretty nasty timing asymmetries built into them. On top of that
you may have asymmetric routing. Up stream and downstream routing is a “two pipes”
process in a lot of head end installations. Again, we’re talking about internet and not
some sort of GPS based system.
To get the accuracy into the 1 ms range on WWV, you would need a pretty good idea of the path
length between you and WWV. If you are looking at ground wave, that is a bit easier than
if you are bouncing off the ionosphere. Just as with WWVB, there probably is a “best time
of day” to run your comparison.
Since you get a lot of ticks, there is no real need to just use one. Feed the audio into a computer and
let it sum them up. Monitoring for 10 minutes does not seem to be overly crazy. That’s still a lot
of ticks. If you dig into the archives, there are some good posts from PHK about doing this
sort of thing with Loran-C.
Bob
On Dec 7, 2017, at 4:29 PM, Bill Hawkins bill.iaxs@pobox.com wrote:
One way to compare any WWV receiver to a local standard is to use the
PPS output of a standard against the PPS tick modulated on WWV. The tick
is five cycles of a one KHz signal derived from the master frequency.
See
https://www.nist.gov/pml/time-and-frequency-division/time-services/wwv-a
nd-wwvh-digital-time-code-and-broadcast-format
It will be a bit tricky to determine the onset of the first cycle amid
the noise on shortwave radio. A computation that determined that there
were just 5 cycles and worked backwards to determine the timestamp of
the beginning or middle of the tick could then allow calculation of the
offset between the standard PPS and the tick. Limit of accuracy might be
100 microseconds.
Years ago, I had a standard calibrator made by Lavoie that had a vacuum
tube WWV receiver. IIRC, the WWV carrier caused a circular sweep on a 2
inch CRT. The sine wave from a standard modulated the intensity of the
circular trace, so that a bright half moon appeared on the CRT and
rotated at the error rate between the two frequencies. On several
evenings the dominant signal varied between WWV and WWVH (identified by
the voice broadcasts). Here in Minneapolis the phase difference between
the two stations was about 180 degrees, causing the bright arc on the
CRT to change sides.
So yes, this could be interesting for a hobbyist, but it won't add
anything to Science.
A MASER is overkill. Heck, so are Rubidium and Caesium.
A naked crystal will be rock solid compared to received WWV.
OTOH, NTP has marvelous mathematical tricks to reduce Internet
propagation delay.
A scheme to reduce varying atmospheric delay would be useful, if there
weren't much better ways to get a standard frequency.
Bill Hawkins
-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces@febo.com] On Behalf Of Patrick
Barthelow
Sent: Thursday, December 07, 2017 7:48 AM
Hello Friends,
I am picking up locally a couple of vintage analog Radio Shack SW time
cube radios, 70s vintage, 3 switchable SW frequencies. Two types, the
one pictured and a Radio Shack model also that has WWV and Weather
channel VHF frequencies.
I am interested in an accurate bench test to compare the analog
shortwave radios time reporting hopefully UT-1 against other available
references. For accuracy, and
repeatability. Could eventually add an SDR to the mix, too.
The 5,10,15 mhz radios obviously are subject to the WWV Ft Collins site,
propagation distance delays, somewhat calculable, and the vagaries of
Ionospheric propagation, and, propagation delays between the antenna and
the measured tap point to the seconds ticks of WWV. I have some
friends,
microwave professionals, who are also hams here in Auburn who may enjoy
doing a bench test, with published results, etc. But wonder if anyone
else would be interested in borrowing a RS Timecube radio (and/or use an
SDR) and designing an accurate bench test against available modern
standards?
We are talking probably HUGE UT-1 errors compared to what this group
plays with, and that is OK but I think still a worthwhile test,
especially if the errors using available and cheap equipment are
predictable, and repeatable.
https://forums.qrz.com/index.php?attachments/dscn1187-jpg.400844/
----- %< ----- [snip of microwave stuff]
Best, 73, Pat Barthelow AA6EG
apol apolloeme@gmail.comloeme@gmail.com
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
The timecube radios were simple superheterodyne AM receivers. I suspect the group delay of the timecubes will be small and fairly consistent due to the low component count,
Yet because of the low quality components performance variability between units will be quite high.
A more interesting test would be with a heathkit 'Most Accurate Clock' GC-1000 which was effectively a HFDO since it used HF WWV signals to discipline its timebase.
On Dec 7, 2017, at 3:05 PM, paul swed paulswedb@gmail.com wrote:
Pat
Way back in the 90s I measured the color subcarrier frequency of
geostationary satellites. That aren't actually stationary.
I knew the quality of the subcarriers for a number of the networks since we
originated the signals. CBS was Cs others were Rb and still others various
Xtals. I had direct access to the references.
I used an HP5360 and homebrew interface collecting the data on a computer.
I was using a wide variety back then.
No matter. I actually could see over long periods the orbital day to day
and seasonal behaviors. By gosh physics and such in action. The reference
was the 5360s oven oscillator that was quite good. I know times have
changed. The reason to do it was simply because I could.
All of that said I will believe the doppler shifts are your biggest impact
so not sure orders of magnitude really help and may actually confuse. You
will have the effects of earth, the moon and the satellites orbit. Now
thats some serious math and thinking. Some place along the line other great
stuff will work to mess with you.
Regards
Paul
WB8TSL
On Thu, Dec 7, 2017 at 8:48 AM, Patrick Barthelow apolloeme@gmail.com
wrote:
Hello Friends,
I am picking up locally a couple of vintage analog Radio Shack SW time cube
radios, 70s vintage, 3 switchable SW frequencies. Two types, the one
pictured and a Radio Shack model also that has WWV and Weather channel VHF
frequencies.
I am interested in an accurate bench test to compare the analog shortwave
radios time reporting
hopefully UT-1 against other available references. For accuracy, and
repeatability. Could eventually add an SDR to the mix, too.
The 5,10,15 mhz radios obviously are subject to the WWV Ft Collins site,
propagation distance delays, somewhat calculable, and the vagaries of
Ionospheric propagation, and, propagation delays between the antenna and
the measured tap point to the seconds ticks of WWV. I have some friends,
microwave professionals, who are also hams here in Auburn who may enjoy
doing a bench test, with published results, etc. But wonder if anyone else
would be interested in borrowing a RS Timecube radio (and/or use an SDR)
and designing an accurate bench test against available modern standards?
We are talking probably HUGE UT-1 errors compared to what this group plays
with, and that is OK but I think still a worthwhile test, especially if the
errors using available and cheap equipment are predictable, and repeatable.
https://forums.qrz.com/index.php?attachments/dscn1187-jpg.400844/
Another question: Re precision frequency measurements of spacecraft
carriers at earth ground stations. I have found a number of MASER labs,
willing to help measure a 70 cm UHF carrier of a satellite planned mission,
circling the moon. Fun, and overkill yes . But I would like to know if
the MASER extra 3 orders of magnitude precision frequency measurement (over
Rubidium, Cesium) is useful, or utterly wasted in measuring a lunar
orbiting spacecraft frequency over as long a period as a month, in a coming
satellite mission? Or, are Rubidium and Cesium and GPS disciplined
references plenty accurate for accurate spacecraft orbit determinations?
Best, 73, Pat Barthelow AA6EG
apol apolloeme@gmail.comloeme@gmail.com
"The most exciting phrase to hear in Science, the one that heraldsnew
discoveries, is not "Eureka, I have found it!" but:
"That's funny..." ----Isaac Asimov
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
On 12/7/17 1:29 PM, Bill Hawkins wrote:
So yes, this could be interesting for a hobbyist, but it won't add
anything to Science.
A MASER is overkill. Heck, so are Rubidium and Caesium.
A naked crystal will be rock solid compared to received WWV.
OTOH, NTP has marvelous mathematical tricks to reduce Internet
propagation delay.
A scheme to reduce varying atmospheric delay would be useful, if there
weren't much better ways to get a standard frequency.
What you are talking about is "better ionosphere modeling", which is
something that a lot of people have spent a lot of time and effort on,
without a lot of success. That said, there are some real time ionograms
out there that are fascinating to watch. It doesn't take a very
sophisticated receiver to receive the signals from a variety of
ionosonde transmitters.
Juha Vierinen has a variety of interesting software:
http://www.sgo.fi/~j/gnu_chirp_sounder/
Juha also has done stuff with measuring the frequency of beacon satellites
Here is a project which mixed the Time Kube IF output back to 10 MHz for
use as a frequency (not time) standard:http://schematicsforfree.com/archive/file/Oscillators%20and%20Generators/Misc/10Mhz%20Frequency%20Standard%20Using%20Wwv.pdf
I believe that the Time Kube uses a 3-transistor mixer / 455 kHz IF
amplifier signal chain, followed by an IC audio amplifier. I would think
that the signal delay inside the receiver from antenna to audio output
would be a couple of hundred microseconds, much less than one cycle of
the demodulated audio “tick”.--
Bill Byrom N5BB
On Fri, Dec 8, 2017, at 07:13 AM, jimlux wrote:
On 12/7/17 1:29 PM, Bill Hawkins wrote:
So yes, this could be interesting for a hobbyist, but it won't add
anything to Science.
A MASER is overkill. Heck, so are Rubidium and Caesium.
A naked crystal will be rock solid compared to received WWV.
OTOH, NTP has marvelous mathematical tricks to reduce Internet
propagation delay.
A scheme to reduce varying atmospheric delay would be useful,
if there> > weren't much better ways to get a standard frequency.
What you are talking about is "better ionosphere modeling", which is
something that a lot of people have spent a lot of time and effort on,> without a lot of success. That said, there are some real time
ionograms> out there that are fascinating to watch. It doesn't take a very
sophisticated receiver to receive the signals from a variety of
ionosonde transmitters.
Juha Vierinen has a variety of interesting software:
http://www.sgo.fi/~j/gnu_chirp_sounder/
Juha also has done stuff with measuring the frequency of beacon
satellites
http://www.sgo.fi/~j/jitter/web/
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.