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
