Hi Jerry,
I had a frequency stability problem, not exactly as yours but both may
be related. The symptoms was the stations appeared very displaced
about 50 % the times I powered up the radio.
Meanwhile I was figuring out what was happening with the calibration I
discovered that unplugging and conecting again the power connector
several times the frequency returned to the right value. After
measuring carefully the offset at different frequencies, I supposed that
the reference frequency sometimes was starting at 199.2885 MHz, since it
was consistent with the measurements. Gerald advised me that the
probable cause was the oscillator and it was not not related to the
software or the DDS.
I ordered a replacement oscillator and received it a week ago. This
weekend I installed it and the problem is gone. It seems that those
oscillators may develop a failure mode that affects stability.
You can do some tests using an external oscillator ( the external
oscillator kit may be improvised following the info) or temporarily
replacing the suspect module with another with a suitable frequency,
since submultiples of 200 Mhz could work. I used a plug in 50 Mhz
module recovered from a computer MB because I was nor concerned with the
spectral purity, only I wanted to be sure that the oscillator was bad.
The circuitry has provisions for single ended or balanced oscillator
output and the multiplication ratio can be set in the console setup.
I hope this may help.
73 de Ignacio, EB4APL
Jerry Harley wrote:
I know this has been beaten to death but I never saw anyone say what
they are experiencing.
I had a big problem in the beginning it was off by 278kc, after the
component change I'm off 200 and drift up to dead on in less than 15
minutes. From the 15 minute mark on I see no drifting.
Jerry Wa2tti
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