[amsat-bb] Re: Dumb question 9600 FSK
Gordon JC Pearce
gordonjcp at gjcp.net
Fri Nov 22 01:36:15 PST 2013
On Thu, Nov 21, 2013 at 03:45:04PM -0700, David W0DHB wrote:
> What mode should your RX be in to receive the 9600 baud FSK telemetry
> downlink signals. USB, FM ??
It should be FM, and you must pick up the signal from before the audio filter. You're looking for "flat unsquelched" in Motorola parlance ;-)
9600bps FSK is generated by modulating the carrier frequency with the digital bitstream directly, after passing it through a filter to round the corners off so it doesn't splatter. As such, the frequency response needs to be flat from DC to whatever the passband of the IF filter is.
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