Haven't seen any discussion on this but lots on cascading filters. If
you have a radio with an IF output (or can modify it to get the IF
out) and a second radio that can receive the first one's IF, you can
cascade them for some amazing results. I did this with a pair of
DX-394's. You get sharper selectivity on AM due to the cascading of
filters, continuously variable selectivity by tuning RX1 off frequency
and RX2 off RX1's IF, extra gain to pull up the weak ones into the
incredible AGC range. With 5kHz steps, tuning across the SWBC bands is
like changing channels on a TV set. In the case of the DX-394, the
overall SSB/CW bandwidth is automatically one-half that of one radio
without any tricky tuning and can be narrowed further if you don't
mind losing the accuracy of the frequency displayed. For more on how I
did it with two of the DX-394, visit
http://groups.yahoo.com/group/RADIOS...4/message/1748 and follow
the thread.

Tom