I've erected a delta loop in my back garden for general shortwave listening,
with a total wire length of 75 feet, fed with 75-ohm coax via a balun. The
balun is a 3:1 turns ratio transformer wound on a small red toroid from my
junk box. The winding on the coax side is about 20uH, and the winding on
the loop side is about 200uH. I've no idea how close to, or far from
optimal this is. I mostly listen to hams on 40 and 80-metres. I've no idea
what the impedance of my loop is on these bands. It would be useless for
transmitting, because it's less than one wavelength, but it seems to work OK
on receive. The noise level is certainly nice and low. My questions is:
what is the impedance likely to be on 40 and 80-metres?

TIA
Andrew.