[BC] am receiver for monitoring at a 20 KW site (add)

[Mark Humphrey]

If you don't mind a little construction project, this tuned filter
designed by DX-guru Dallas Lankford might do the trick.   It's a
variation of the air-coupled approach Richard described, with both
coils mounted inside a shielded enclosure.   For proof of selectivity,
see the analyzer shots on Page 3:

http://antenadx.com.br/PDF/Antenas%20ativas/MWPhaserno2%20(2).pdf

Here's an alternate form:

http://antenadx.com.br/PDF/Acopladores/SWFilterno2.pdf

I haven't tried either of these, but they look quite sharp.

Mark