On a sunny day (Mon, 7 Feb 2022 19:41:57 -0800 (PST)) it happened Sid 03
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sidw...@gmail.com> wrote in
<
9bdd5c05-255b-4802...@googlegroups.com>:
>Jan, looking at all those projects from the link(s) that you posted, most talk about minimum frequency drift.
>I thought that crystal controlled radios did not experience frequency drift, or at least negligible drift ?
Yes crystal controlled, in this case phase locked loop should have negligible frequency drift
for an _FM_ modulated radio transmitter,
As long as the loop is locked that is.
But if you have a 2.4 GHz transmitter locked to a 10 MHz crystal
then the 10 MHz is multiplied by 2400 / 10 = 240, and so is its error.
If the 10 MHz now drifts 10 Hz (1 part per million, so 1 ppm) then the 2.4 GHz will drift 2400 Hz.
If the modulation type was SSB then a 2400 Hz shift will be totally out of audio range!
So a solution in a case like that (QO100 ham satellite) is to lock the 10 MHz crystal to for example
a 10 MHz Rubidium frequency source that has a much lower drift than 10 Hz.
Or use some other precision 10 MHz source.