Jan, I have been doing 0.1ppm for a long time. Long before digital
readouts the ARRL had a frequency measurement test. It is a lot
easier now. 0.1 ppm which is 1 Hz at 10 MHz. The fastest way to get
a frequency measurement of 0.1 ppm at 2.5, 5, 10, 15, and 20 MHz
WWV or WWVH is to use the sound card. Tune 1000 Hz high in LSB
or 1000 Hz low in USB and look at the frequency with digipan or some
other sound card FFT program. Select AFC so the program locks on the
carrier. The frequency readout is good to 1Hz. I checked that with a
frequency counter. You can use a lower frequency like 100 Hz offset
and get even more resolution. As I write this I am measuring 1010.8 HZ
using MixW FFT software on a Pegasus tuned to 10.001 MHz LSB. It
measures 994.5 Hz tuned to 9.999 MHz USB. That is a 1ppm error
on LSB and 0.5 ppm on USB. This with N4PY Pegasus sotware.
The error is getting less as the Pegasus warms up.
Regards, Jim FitzSimons W7ANF
-----Original Message-----
From: Jan Ditzian <ditzian@alltel.net>
To: tentec@contesting.com <tentec@contesting.com>
To: <tentec@contesting.com>
Date: Sunday, March 19, 2000 12:14 PM
Subject: Re: [TenTec] Accuracy (long)
>
>Al, W6LX, just wrote a treatise on accuracy that should be read with
diligence. I
>recently asked for assistance on this reflector and received it, and I
realigned
>the 10 mHz oscillator and the bfos. My Elmer for this work was a local
Physics
>professor and ham, Mike, K8LG, who has fancy signal generating and
measuring
>equipment for his work in the VHF and UHF area.
>
>We measured an 80 Hz error at the 10 mHz oscillator, and I was ready to hit
the
>ceiling, but he immediately did the math to show how small an error that
was. We
>got it to 20 Hz and then he said that going further was silly, since he
could not
>even guarantee that his $600 counter was necessarily better than that
without
>calibrating it against his $1500 reference oscillator, which, at the
moment, was
>not available to us. Besides, the capacitor is so large that every bump
made a
>random jump of far more than 20 Hz.
>
>Al is right on, and I will be more careful about what I say about Ten-Tec
frequency
>calibration in the future. Not that we should not try to keep things
right, just
>that we have to realize that these errors are to be expected over time. By
the
>way, I would like to add a public "thank you" to Scott at Ten-Tec and
Steve, N4LQ,
>for their recommendations.
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