Hello Jim &LF-group,
is the TX-antenne detuned, while you're receiving on the loop? (so ther is
no nearfield-coupling from the big one to the loop)?

Regards, Peter, dj9dw

Dear Peter, LF Group,

Yes - The antenna is matched with a series loading coil, and a seperate
matching transformer, connecting to the TX via 50ohm coax. Essentially, the
TX/RX relay open circuits the feed to the antenna, leaving the matching
transformer secondary inductance in series with the loading coil. This adds
several hundred uH to the loading inductance, which seems to be enough to
detune the antenna to the point where it has no detectable effect. If the
transmit antenna is not detuned, it is possible to hear some increase in
50Hz noise on the loop antenna, but the increase is not very dramatic.

Cheers, Jim Moritz
73 de M0BMU