Thanks fo sharing. That noise is surely not local: we have powerlines
and industry nearby, LAN in the roofspace, streetlights and so on. I
guess that I'll try a full-wave loop directly laying on the roof,
feedpoint will be low impedance but how low? 5, 1, 0.5 ohms?
Maybe I can transmit to it too if the currents are'nt too high? Is
there an antenna design that has high feedpoint impedance to start
with, so the impedance would be usable when antenna is layd directly to
the roof?

Andrus