On 4/24/20 5:52 AM, David J Taylor via time-nuts wrote:
Hi
The “wiggles” he is chasing are about 2-3 Hz (by eyeball on his charts).
At 2.4 GHz,
that is a fairly convenient ~1 ppb. The Z-3801 (if it was in good
health) should be easily
able to hold that level of performance. It’s not clear which MD-011 he
is using, but it is
a pretty good bet it will also hold that level as well. The usual
disclaimers about good
satellite view for the GPSDO’s would of course apply.
Substituting a typical telecom Rb for either device would likely also
allow the wiggles
to be observed (or not). That would take out the whole dependence on GPS.
(Yes I realize those comments are probably better directed to those
involved ….).
Bob
It's a fascinating writeup - the author does time-nut like stuff at
work, so he looked at the possibilities - is the GPSDO at Bochum
screwing up (can't actually get in because of COVID-19) - so he compares
with a locally generated uplink.
He also compares with the signal from an uplink from Mauritius, so the
Doppler is slightly different.
I'm going to guess just what he said at the end - some sort of thermal
thing on the spacecraft.
========================================
If you follow his Twitter feed:
https://twitter.com/ea4gpz
I think it's all but certain that it's the local oscillator in the
satellite-borne transponder is the cause of the problem. He's looked at
an engineering beacon on the satellite too. The orbital calculations
involved need to be quite accurate.
I thought it might interest those chasing the ultimate precision!
Probably ought to change the title of this topic, but I'm unsure of the
protocol here about so doing.
Cheers,
David
_______________________________________________
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe, go to
http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.
