I agree there is nothing wrong with QO-100 - our investigation mostly focused on the frequency accuracy of the transponder LO to determine the source of the frequency offset that was observed, not so much on its frequency stability. Nevertheless, the measurements did show some interesting features related to stability as a nice side-effect
I have also updated my blog post to correct the (likely) incorrect hypothesis that the wiggles are caused by stationkeeping maneuvres, this is based on the excellent work by EA4GPZ and others.
Thanks Peter and your team for the great work in making a Geostationary satellite available to the amateur community!
Wouter Jan PE4WJ
Disclaimer: I cannot and will not give any technical details of the QO100 transponder due to NDA. But I think it is obvious that any space-qualified transponder oscillator will have very good stability values so for the sake of simplicity we assume it is non-significant compared to the numbers above....
73s Achim, DH2VA
Ok, it seems fair to me. However some features of the "Melco" Satellite Platform DS2000, the same as Es'Hail-2, are known.
Here the characteristics of the Beacon (commercial). The same that we find on V. 10.706 GHz.
Maybe we can start from here?
not everyone is able to receive this Beacon as it transmits on MENA Beam
I agree there is nothing wrong with QO-100 - our investigation mostly focused on the frequency accuracy of the transponder LO to determine the source of the frequency offset that was observed, not so much on its frequency stability.
Hi Wouter Jan,
Thanks! Yes - absolutely correct regarding frequency accuracy and stability.. indeed both are covered and referenced above, while originally analyzing the short term frequency stability, an offset of ~70 Hz in frequency accuracy has been indeed observed.. I should have better emphasized this...
This thread is ancient, but nevertheless: You can monitor frequencies of the satellite oscillator yourself with a round trip measurement experiment. I found this: https://pa1ejo.wordpress.com/2…00-satellite-transponder/ My verdict is : -63.7 Hz bias for the satellite oscillator and -6 Hz for relativity. The rest of the frequency offsets correspond the Doppler effect due to satellite orbit dynamics and some maneuvering which you get from the TLEs. The satellite beacon is according to me an injected signal from Doha in Qatar, and I think there is a reason to keep the total Doppler and oscillator effect negative, so that you can't have a confusion on the sign of the correction.
This confirms my suspicion because of the factor 0.814 that I mention in the blog. I get the best match between my own Doppler frequency offset measurements and the PSK beacon frequency offsets when I apply the 0.814 to both the PSK beacon measurement and my own Doppler measurement. In other words, the PSK and beacon signals must go through the same 2.4 GHz uplink in the same way as I do the roundtrip measurement. My last point is, why not apply the approx -70 Hz offset on the ground so that you only get to see the Doppler from the satellite?
Noticed that the frequency offset (the -70 Hz) has shifted upward by about 20 to 30 Hz. The early morning PSK beacon goes now to positive a few Hz, it used to be 30 Hz negative. Is this deliberate, is there any information?