First, a big thanks to Simon Lloyd-Hughes, G8AFN, G3XDV, G3RXH, G4FKK, G0MRF and G3YXM for encouragement, comments and ideas. All very useful stuff which is helping me to work on the noise problem, a
I went out again with the Walkman, listening to a peak around 1340kHz, but still couldn't get a consistent fix on it. Walking around adjacent blocks, the strength and nulls vary in a confusing way,
Another possibility for the ultrasonic rx that I have used successfully for the same purpose is a standard gas leak detector as probably used by BT cable jointers etc. Controllers for strings of stre