This system was set up for LF, that is frequencies up to 138khz, but will probably work above that. It's simply a 20-turn square frame with twin flex loudspeaker cable feeding a balanced input preamplifier I've been working on. For a while I tried various circuits, some off the internet, but some didn't work and most were unsatisfactory. This one has received a 136khz signal using WSPR15 from a little under 5000km, considering it was received "through" a 200 ft limestone cliff from the NW (USA) direction I was pleasantly surprised.

The antenna is 1m/39 inches square and currently only about 2.5m/10 feet above ground with 20 turns of thin flexible wire, about 22swg/awg. The feeder cable is cheap twin and probably at least 20pF/metre capacitance. If the preamp is successful with a variety of applications I can post the circuit (jpg file) if anyone is interested.