[amsat-bb] Re: Dumb question 9600 FSK

[David W0DHB]

Thanks Gordon and others.

Is there any SDR software that supports the FCDP and will demod FM properly
for 9.6K FSK ?

Dave

-----Original Message-----
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
Behalf Of Gordon JC Pearce
Sent: Friday, November 22, 2013 2:36 AM
To: amsat-bb at amsat.org
Subject: [amsat-bb] Re: Dumb question 9600 FSK

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.

-- 
Gordonjcp MM0YEQ

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