[amsat-bb] Re: ARISSat telemetry and Doppler tuning

Phil Karn karn at philkarn.net
Sun Aug 21 00:01:04 PDT 2011

On 8/20/11 6:40 AM, Ronald G. Parsons wrote:
> With these two changes, although the Doppler correction may drift off,
> it does so very smoothly, which I assume allows the decoding of the BPSK
> data to be more accurate.

Yes, the closer you keep it the better it'll work. Errors of up to +/-
50 Hz are fairly negligible, but beyond that it starts to degrade. The
demodulator searches +/- 200 Hz in 100 Hz steps around a nominal carrier
frequency of 1500 Hz. I should probably have made it search a wider
range but with that much mistuning the sidebands would start to be
clipped off by the edges of a typical SSB filter.

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