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QCX+ Menu 8.5 Ref frq

 

I would like to know if I can apply the following procedure to calibrate the Ref frq without GPS?
Using a QCX+ 20M Band I would go to WWV 15MHz and read precisely the frequency for a zero beat. If I read 15.003.00 could I modify menu 8.5 to read 25.005.000 with the TCXO and have a more precise QCX+?
73 - Pierre - FK8IH
 

You can do some trial and error yes. ?
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However all the QRP labs TCXOs I’ve seen are within a few HZ of 25MHz and that’s a beat note /error you couldn’t hear/zero sufficiently accurately by ear?
 

Hi Pierre. Since you indicated a reference frequency of 25 MHz, Bruce correctly assumes you have the TCXO option installed in which case you shouldn’t need to worry about calibration. If you don’t have the TCXO installed then the reference frequency is 27 MHz and your procedure should work ok to get close however getting exact zero beat may be difficult since the audio rolls off at the low end.?

Good luck ….73 …. Ron

On Thu, Apr 3, 2025 at 20:41 Pierre - FK8IH via <jb.gallauziaux=[email protected]> wrote:
I would like to know if I can apply the following procedure to calibrate the Ref frq without GPS?
Using a QCX+ 20M Band I would go to WWV 15MHz and read precisely the frequency for a zero beat. If I read 15.003.00 could I modify menu 8.5 to read 25.005.000 with the TCXO and have a more precise QCX+?
73 - Pierre - FK8IH
 

I like to participate in the ARRL FMT runs.?So . . .?
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I have investigated frequency response accuracy of my High and Low band QDX's, my HB QMX and my QMX+.
Don't have a QCX so can't speak direct to that model.?
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All have been within a hertz or two or better, right out off the assembly bench when checked with 2 different Leo Bodnar Precision GPS Disciplined Clocks units.? I have found that I can tweak the TCXO system setting by a few hertz , from as little as +2 to a high of +10 on one band for best frequency response.? Be advised that the best delta will vary a bit ( maybe 0.5 Hz worst case) from band to band in a given radio.?

I use FLdigi on the Frequency Measurement Test OpMode. Found it to be quite useful and instructive in showing things like warm-up drift, probable doppler shifts of received over the air signals and subtle changes ( hundredths (0.0x Hz) or less of shifts) just sitting on the bench in response to my heat or AC cutting on and off.? And there will be a bit of offset needed to completely correct for the FMT modem response on the particular computer on which you are running the FLDigi program.?
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Now having said that, I have spent hours measuring and analyzing over the air received WWV and CHU signals and its a rare band on a rare day & time, on a rare day of overall radio 'quiet' when the signals are rock solid as seen in FLDigi.? You have to be located inside the first skip zone of the transmitters for consistency in that.?
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And I'll bet for actual Ham Radio Operations, all the Q's will be just fine as assembled.?
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There is LOTS of interesting information, articles and How-To's for Frequency Measurement Testing with relatively simple and inexpensive methods these days.? ?Just give it a Google and wade in.? There's even a FMT-NUTS group.io.?
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GREG? KI4NVX

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