The hotel wiring is a very complex load. That's why the coupler had so many choices. I had taken an old RS VOM, added a whip antenna and a ground wire (gnd prong of an outlet or clip to the AC housing). Added a germanium diode to the 3Vac circuit.
Went back to check the circuit. My bad. Series cap and shunt coil. Acted as an "L" Z-match. Running thru the coupler switches, got readings from barely a bump... to a little over a volt. Left her there, and KULP was on the air.
Yeah, the greater distance in wavelengths, the less signal. Like a leaky pole insulator. MW goes for miles, but UHF might only be a pole span or two. Had RF jumpin' outta the walls. 40m probably had a dozen nodes around the hotel. An omni radiator!~!~!
Cunning, Crafty, Clandestine. Free Radio for a Free People. The FOX.