Re: U3S drift/chirp - again!
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Ian
Additionally to what others have said...?
On your image it seems that the gap between transmissions is well under one minute. Is this actually two consecutive transmissions or did you switch off and on again or something?
If that is really how short your gap is, it may explain it. It is certainly not enough for the 4 minutes of calibration that you configured. So the calibration will never complete, and therefore will have no effect. This could explain why the frequency is off. Park modes will not have any effect either because there is never any idle time between cycles when the unit is not trying to calibrate.
Excuse me if I misread something and I'm writing nonsense. It's been another long day!
73 Hans G0UPL? ?
On Nov 30, 2017 10:32 PM, "Bob Sutton via Groups.Io" <zl1rs= [email protected]> wrote:
I assume you are using a 'standard' QRP-Labs synth board and not the
OCXO version.
What Park Mode type are you using Ian??
Examples:? In mode 2 the park mode is inactive during that rather
long calibration time you have, there may not be enough time after
calibration ends and the QRSS starts for the park mode to 'warm up'
the synth again.? In mode 4 the park mode is active all the time
(during TX, between transmissions, and during calibration).? Keeping
the Si5351A 'busy' with continuous park mode activity might help
that 'initial hook' of drift.
Another possibility if the QRSS transmission is the first in the
sequence, is to add a 'dummy transmission' as another "mode" before
the QRSS "mode" (e.g. maybe a CW ident?) to take up the initial
drift hook.
No idea why the transmission might appear to be 20Hz off.? The 20
240 Cal Time setting should set the U3S to within a couple of Hz at
28 MHz ... but now the Ref Freq has settled you might try something
a little finer, like 01 240? (and as above, 240 is longer than is
probably necessary).
73, Bob? ZL1RS
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