[amsat-bb] Re: ARISSatTLM

Phil Karn karn at ka9q.net
Sat Aug 6 12:17:54 PDT 2011

On 8/6/11 9:31 AM, N0JY wrote:
> I'm having trouble getting telemetry.

Jerry, is this a night-side pass with the satellite in low power mode?
The coding is not optimal for a signal that's present only a small
fraction of the time, as it takes 16.384 sec at AOS to "fill the pipe"
in the de-interleaver used to combat fading. It's barely done that when
the transmitter turns off again at 40 sec.

It works much better on the day-side passes with a continuous signal,
even if it's fading deeply.

The CW beacon is 1 kHz below the (suppressed) carrier of the BPSK-1000
beacon. Make sure your radio is in USB mode and accurately tune the CW
beacon so that it comes out at 500 Hz. This will center the BPSK at 1500
Hz. It extends from 500 to 2500 Hz (2 kHz total bandwidth) between
spectral nulls. That's not much narrower than a regular SSB filter, so
make sure your passband shift filter, if any, is set to pass it.

73, Phil

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