Many thanks for your time Gents, The antennas were intended for outdoor use
and constant handling. being encased in hard plastic obviously enhances
those functions. My experience has been at the other end of the spectrum so
to speak and I (incorrectly) assumed an antenna picks up an electrical
signal. Putting a layer of insulating plastic on it seemed contradictory. If
antenna is detecting magnetic signals obviously a different story.
When I mentioned impedance I mislead you. Wasnt referring to antenna
impedance but the impedance looking back form the recieving antenna to the
signal source ( thats what us old analogue designers do, Norton/Thevenin
equivalent circuits etc !!!!) and the effect on that a layer of plastic
has.
Your combined efforts have answered a lot of my questions, thanks for your
time.
Cheers
John
"Rob" wrote in message
...
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.