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Re: choice of IF frequencies



John Stephensen, KD6OZH <kd6ozh@gte.net> wrote:

>Direct conversion radios work nicely for SSB, AM and PM.
>The only problem for me is that they can't support FM
>reception and almost all AMSAT digital satellites have
>a FSK downlink.

Hence the reference to *I/Q* baseband processing. The
information to demodulate FM is there. You just need to
use it, rather than throw it away.

I'll worry about 30 dB carrier suppression when I start
receiving satellite signals that are loud enough to hear
a carrier that is 30 dB down. A little bit of carrier
to lock a PLL on to is handy anyway. If it's good enough
for NASA... :-)

Sideband suppression is a non-issue with DSP. It is, in
any case, also a non-issue with zero-IF/Weaver/3rd Method
radios. Though for different reasons.

Laura Halliday VE7LDH     "Que les nuages soient notre
Grid: CN89mg               pied a terre..."
                                   - Hospital/Shafte

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