I live in an apartment complex with 980 units, all of which are outputting some electrical noise. This makes copy on the low bands very hard. A small receiving loop helps; it has very deep nulls and makes listening on 80 and 160 more pleasant.

The receiving loop goes on a tripod in the living room.

The loop is 3 feet square. It's two turns of #20 insulated wire on a bamboo frame, resonated with a 0-300pF capacitor for 80m (needs 150pF or something, I think), with a 500pF fixed cap with alligator clips for 160m. (550pF required, total. You can see the 500pF cap dangling from the velcro straps in the picture. The antenna is currently set up for 80m.) I measured the inductance of the loop with my MFJ analyzer, then picked the resonating caps. Coupling to the loop is done by a 16" square loop that connects to coax.

Click the schematic for a larger version.

The other end of the coax has a 1:1 isolation transformer to isolate the coax shield from the rest of the grounds. I think this is not at all necessary, but it's there for an eventual try at a low noise receiving inverted L that is transformer coupled and has a separate ground. This goes into a changeover relay that is currently footswitch operated but will eventually be operated by the TX GND on the FT-857 and/or its cousin on the TS-440S. You can't transmit into this antenna; the relay lets me stomp a switch and go into transmit.

Here's the RX loop / main antenna T/R relay (black) and some coax switches.

I've found that this loop needs to be in the middle of the living room for proper nulling. This puts it about 10 feet from the radio. Now, it needs frequent adjustment for resonant frequency and null direction, so I need to be able to see the radio's S-meter from across the room. I've found that the MTR setting for the backlight color on the FT-857 is useful for this; the backlight changes from blue through purple to red as signals get stronger; this plus audio lets me peak the tuning and find the deepest null from too far away to see the meter box.