Ian wrote:
"John" wrote in message
. au...
My question is how do they work?. If they are detecting electrical fields
how does increasing source impedance by 100,s of megohms improve things?.

Pardon? The coating or conduit shouldn't affect the impedance of the
antenna. The radio signal should pass through the plastic and hit the metal
antenna element.

Apparently you have missed the interesting discussions with our Polish
friend.