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I'm trying to find some 455kHz filters suitable for FM +/- some doppler. Ideally, 30kHz wide and fairly small

We did that on the uplink receivers for PCSAT-1 and -2 so that uplink doppler on UHF was pretty liberal. We used the old xtal controlled HAMTRONICS receivers, with the "wideband" and "9600 baud" options to make the receiver about 30 KHz wide. This of course suffered about 4 dB performance loss, but with a 25W uplink, the 4 dB was an insignificant loss compared to the ablity to hear a signal with +/- 6 KHz or more Doppler without splatter.

Bob, WB4APR