[amsat-bb] Re: ISS Repeater
bruninga at usna.edu
Tue Dec 30 19:09:02 PST 2008
> The ISS radio system currently supports
> only one mode at a time. The current
> L/v configuration is scheduled to be
> active until Saturday, Jan 3.
> And I don't think you can't get into
> the 1.2 GHz uplink without a yagi ;)
The most important thing is proper Doppler compensation. At 1.2 ghz the Doppler is from -25 KHz to plus 25 KHz or so, and you have to be within a few KHz, or your splatter will not open the squelch of the repeater.
With 11 full Doppler steps during a pass, you have to nail it exactly or you dont get through he 12.5 KHz filter. Plus I bet even being 2.5 KHz off between each step and speaking fully, will splatter so much as to keep the squelch closed.
So in that case, there are 22 discrete windows of opportunity, only half of which are useable, so it takes real care to get through. Of course, I am only kibitzing, since I have not tried it, but all the signals I have heard do NOT seem to be suffering power limitation, but all seem to be suffering off-frequency splatter and therefore squelch unreliability.
Maybe setting narrow band deviation (as used in europe) will reduce the spaltter and keep the squelch open better.
I'd suggest setting narroband deviation too, to help prevent
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