Re: K2 Calibration using WWV

Posted by Matt Osborn on Apr 25, 2006; 10:05pm
URL: http://elecraft.85.s1.nabble.com/Need-help-for-sick-K1-tp389102p389125.html

There are three different signals on WWV 100, 400 & 500 Hz.  I assumed
that if those signals had the proper relative frequencies that all I
had to do was check the absolute frequency. The  Elecraft 2T-gen fit
that requirement with its two frequencies of 700 & 1900 Hz.

I prefer the PSK31 waterfall display to that of Spectrogram as the
trace readily shows any drift (there is none, but it's the warm fuzzy
I'm after).


On Mon, 24 Apr 2006 19:44:16 -0700, Darrell Bellerive <[hidden email]>
wrote:

>On April 24, 2006 01:56 pm, Matt Osborn wrote:
>> WWV provides a BCD subcarrier at 100Hz that is always present.  Using
>> HRD's PSK31 (it's free; thanks Simon!) it is a simple matter to adjust
>> the tuning to the proper frequency.
>
>Please expand on this. I have never used a PSK application, but how would it
>detect the subcarrier is exactly at 100 Hz? I suspect the software is using
>the soundcard clock as a reference and that wouldn't necessarily be very
>accurate.
>
>Seems that the K2 can be set very exactly using Wayne's method
>(http://www.elecraft.com/Apps/K2%20C22%20Adjust%20App%20Note.pdf) but it
>requires properly zero beating WWV. Using an audio spectrum analyzer such as
>Spectrogram to detect WWV's broadcast tones is dependant on the accuracy of
>the spectrum analyzer.
>
>The spot tone generator in the K2 seems to derive it's clock and therefore
>it's frequency from the MCU and the 4.0 MHz oscillator set by C22, so the
>spot tone frequency will be dependant on the setting of C22, which is what we
>are trying to set in the first place. So using this tone as a reference does
>not look like it will work.
>
>Having a calibrated audio spectrum analyzer may be one solution. Perhaps a
>musical tuning fork via a microphone could be used to calibrate the audio
>spectrum analyzer. How accurate are tuning forks?
>
>Wayne suggests just listening for zero beat, one should be able to get within
>about 15 Hz.
>
>The trick seems to be how to tune the K2 to exactly 10,000.000 kHz and at the
>next step up of the vfo be at 10,000.010 kHz. Seems a lot like an ARRL
>frequency measuring contest. :-)
>
>What tricks have others on the list found to tune WWV to within 1 Hz or less
>without expensive professionally calibrated test equipment?
>
>73,
>Darrell VA7TO K2#5093

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