[amsat-bb] Info of Chinese Launch 2016-066

[Dani EA4GPZ]

El 20/11/16 a las 19:14, Alan Kung escribió:
> Hi Drew,
> 
> 
> Thanks for your report! I think the problem is not lack of electric
> energy, CAS-2T is an 2U structure, we installed solar panels on five
> sides with 30% efficiency, average total power about 2.2 Watts, the
> power budget: CW Beacon=0.5W, FM Transponder=0.7W, OBC=0.05W, TT&C
> Receiver=0.12W, Total=1.37W, normally there is some superfluous power
> to supply to heating resistances.
> 
> What problems are I think: First CAS-2T was not separated from the
> launch vehicle, final stage of the lauch vehicle is much bigger than
> CAS-2T satellite, and it keeps self spin in approx. 7 seconds per
> circle. It lead to the antenna radiation pattern becomes chaotic, the
> gain at some positions become much lower and is accompanied by a
> parasitic amplitude modulation. On the other hand, in order to avoid
> chaotic signal on VHF from land in East Asia to disturb the Satellite
> uplink , we adjusted the uplink receiver squelch at very deep
> position, it makes the transponder opening sensitivity less than
> -110dBm at RF input port of the receiver.
> 
> So I think the solution is only to improve the uplink EIRP, some of
> the high schools' club stations here using 3 meters boom antennas
> with approx. 50W RF power to get through the transponder well.

Hi Alan,

Given my own observations and all the reports I've heard from other
Amateurs, I don't agree with your explanation.

It is not a problem with the squelch or the uplink EIRP. The FM comes on
even with an uplink of 5W to a 7el yagi. The problem is that the
downlink is not a clean FM modulation, but some sort of "rubbish".

I haven't heard of anyone that succeeded to downlink his signal through
the FM transponder fine. People using big or small groundstations have
the same problem.

What is this high schools thing? Do you mean that they were able to use
the CAS-2T FM repeater successfully? If so, can anyone with a big
groundstation give this a try and preferably do an SDR recording of the
downlink?

More info:
http://destevez.net/2016/11/some-measurements-of-cas-2t-on-orbit-25/

73,

Dani EA4GPZ.