"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.

Are these antennas intended for indoor use where the plastic coating is for
decorative effect?
If the antennas are intended for outdoor use then substantial coating or
conduiting will increase the wind loading of the antenna It also needs to be
u/v stable.

Regards, Ian.