ARRL FMT April 13 - 0215utc (K3EXREF)

[Edward R Cole]

Might be a great way to demonstrate the new accuracy of the K3EXREF!
http://www.arrl.org/frequency-measuring-test

Any tips on how one measures the frequency in these tests?


73, Ed - KL7UW, WD2XSH/45
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[Bruce Beford-2]

Hi, Ed. Here's a group that I belong to:

http://groups.yahoo.com/group/FMT-nuts/

 

Many of the members there are true time/freq measuring nuts. The Midwest
VHF/UHF society run their own FMTs at different times of the year. You can
also Google time-nuts. If you don't mind a simplistic overview, the audio
output of the radio is sent to the sound card of the PC. One uses an audio
analysis program like Spectrum Lab or Spectran to analyze the frequency of a
beat note. Sometimes that is just watching the carrier of WWV while in CW
mode, sometimes a very accurate signal generator is also input to the RX at
the same time as the signal under test, and the difference measured.

 

Doing the FMT can be a great challenge and a lot of fun. However, getting
really good at it can take some work (which is part of the fun). Often
times, ones measurements are limited by the Doppler shift of the ionosphere
(yes, there is Doppler even at HF). In the finally analysis, one sometimes
has to resort to "guessiplication" for deciding what frequency to submit as
your measurement.

 

All that said, on one of the FMTs done a year or so ago, I was able to get
within 9 milliHertz of actual carrier frequency on a 20M test out of the
Midwest. I used an HPSDR Mercury DDC receiver that was phase locked to a
Trimble Thunderbolt GPSDO. That's about 6 parts per ten trillion. And I
wasn't even the closest...

 

73, Bruce N1RX

 

> Might be a great way to demonstrate the new accuracy of the K3EXREF!
> http://www.arrl.org/frequency-measuring-test
> Any tips on how one measures the frequency in these tests?
> 73, Ed - KL7UW, WD2XSH/45

 

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[Nate Bargmann]

* On 2011 08 Apr 02:26 -0500, Edward R. Cole wrote:
> Might be a great way to demonstrate the new accuracy of the K3EXREF!
> http://www.arrl.org/frequency-measuring-test
>
> Any tips on how one measures the frequency in these tests?

Checkout Fldigi:

http://www.w1hkj.com/Fldigi.html

It is a Freq Analysis mode that will output recorded frequency error to
a CSV file that can be imported into a spreadsheet and massaged as
needed.  After that the options become more expensive.

73, de Nate >>

--

"The optimist proclaims that we live in the best of all
possible worlds.  The pessimist fears this is true."

Ham radio, Linux, bikes, and more: http://www.n0nb.us
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[Tony Estep]

On Fri, Apr 8, 2011 at 2:24 AM, Edward R. Cole <[hidden email]> wrote:

> Might be a great way to demonstrate the new accuracy of the K3EXREF!
> http://www.arrl.org/frequency-measuring-test
>
> Any tips on how one measures the frequency in these tests?
>
> Well, one way to do it is described in the docs for WSPR 2.0:

http://www.physics.princeton.edu/pulsar/K1JT/WSPR_2.0_User.pdf

<http://www.physics.princeton.edu/pulsar/K1JT/WSPR_2.0_User.pdf>
You can calibrate your rx within 1 hz using the technique desribed in the
manual, then just read the test frequency off your dial. Several WSPR users
were among the top finishers in the last test using this technique.

When you first read it, it sounds harder than it is. You just calibrate at
several different reference frequencies, then generate a correction function
for dial error vs. frequency. If you like this sort of stuff, check it out.

Tony KT0NY
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[Bruce Beford-2]

Poor math skills early in the morning. 9 milliHertz out of 14 MHz is about 6*E-10, or 6 parts per ten Billion, not Trillion. Still, not too shabby for a first FMT attempt. -Bruce, N1RX



N1RX wrote:
> All that said, on one of the FMTs done a year or so ago, I was able to get
> within 9 milliHertz of actual carrier frequency on a 20M test out of the
> Midwest. I used an HPSDR Mercury DDC receiver that was phase locked to a
> Trimble Thunderbolt GPSDO. That's about 6 parts per ten trillion. And I
> wasn't even the closest...



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