For a direct conversion AM receiver for the commercial broadcast band
(550-1710kHz), could someone suggest appropriate low pass filter
specifications? I'm looking at a standard (cheap) superhet receiver with a
two stage transformer coupled IF amplifier/filter, and then end up with a
bandwidth of +/3kHz (around 455kHz). Hence, this would be equivalent to a
4th order filter with a corner frequency of 3kHz -- correct? I was thinking
I'd need somewhat more aggressive (but wider) filtering than this (more like
an 8th order filter with a corner at 5kHz).

If a commercial AM station is transmitting at, say, 550kHz, is it a safe bet
that the FCC wouldn't have stuck another reasonably powerful station at
560kHz, the next 'channel', in the same geographic location? That they'd at
least wait until 570kHz to do so? Historically I would think they'd have
had to do so in order to allow these simple IF transformer coupled
amps/filters to perform satisfactorily.

Thanks,
---Joel Kolstad