[time-nuts] Re: 10 MHz TCXO periodically jumping 20 mHz up and down

[Andy Talbot]

A while back I purchased a low cost TCXO which I then used as the reference
for a synthesizer generating 10GHz.  Listening to the output on an SSB
radio, the tone was hopping in a random fashion over four frequencies,
spaced a few tens of Hz apart.   This was surreal!  I had, at that time,
been building Multifrequency Shift Keyed data sources ( for WSJT modes) by
programming synths directly, but this wasn't the case here.   Yet the
hopping tones sounded just like the modulation I would eventually be adding.
Double checking, then again, then again. that I hadn't inadvertently
programmed the synth controller PIC with the wrong code, had to come to the
conclusion it was the TCXO using a PRN sequence to effect digital
temperature/frequency compensation.    At its 10MHz fundamental, each hop
would have been a few tens of millihertz.

But it was very weird at first, hearing what sounded like a familiar
modulation on a synth that wasn't programmed to generate it.  There were
four tones hopping in a (presumably pseudo) random manner, and the WSJT
mode I was going to use, JT4, had... four tones that hop around.

Andy
www.g4jnt.com



On Fri, 18 Feb 2022 at 10:19, Erik Kaashoek <erik at kaashoek.com> wrote:

> During long term testing of some 10 MHz TCXO  the output frequency seems
> to jump within one second 20 mHz ( millihertz) up in frequency  every
>
>