Reg Edwards wrote:

They who discuss "power radiated from the feedline", yet are unable to
measure (in watts) or calculate (in watts) the MAGNITUDE of the
effect, belong to a set of waffling old wives.


Those who take no precautions to prevent their feedline from becoming
part of the antenna, belong to a set of people who don't even know what
their antenna IS.

There's a part you call "the antenna", and another part you call "the
feedline". Wishful thinking will not stop RF current from flowing
directly from one to the other.

How is it possible to decide whether or not a choke or balun is
needed, and where to locate it, unless the magnitude of what one MIGHT
wish to prevent is known.

Try a clamp-on RF current meter, a little modeling... or even a little
common sense.

There's a place called "the feedpoint" where the antenna and the
feedline are connected directly together. Might that be a good location
for a choke to keep them separate? Yes, it almost certainly would.

Chokes may also be needed at other locations, but it's hard to justify
anywhere else as your *first* choice. (The exception is the Carolina
Windom and similar antennas where part of the feedline is intended to
radiate. But even there, they put a good choke at the point where they
want RF currents on the feedline to stop.)

Queen Elizabeth 1 of England had the good sense to take a bath every six
months "whether I need it or not". If you don't know whether your
feedline smells of RF, then follow her excellent advice and use a
choke.


--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek