"mm" wrote in message
...
On Sun, 12 Feb 2006 13:25:44 GMT, "Ralph Mowery"
wrote:


"Tony Hwang" wrote in message
news:meBHf.602959$ki.30465@pd7tw2no...
jg wrote:


Hi,
Twin lead also has better quality foam ones not the skinny twirly kind.
Coiling up extra coax is not a good idea it can act like RF choke and
could lower signal level.
Tony

Coiling up extra coax wil not make it like a RF choke and will not lower
the
signal level. As long as the coil diameter is large enough that the
center
conductor does not cut into the iner insulation and short to the shield,
nothing on the outside of the coax will affect the strength of the
signal.
The signal is carried on the inside of the outer shield. Coil up all the
extra you want. One thing that will affect the signal is if you have way
too much coiled up (like 20 or more feet) is the extra loss in the length
of
coax. YOu will get the same ammount of loss if it is coiled or just ran
in
a line.

If you are transmitting , coiling up the coax may have a benifit as it
will
act as a choke and keep the transmitted rf that is coupled from the
antenna

You sound like you know what you're talking about, but one thing gets
me. Here you say it will act as a choke and at the start of the
previous paragraph you say it won't. Why does transmission have a
different result from reception, or is there some other difference?

from getting back to the transmitter. Discussion on this is beyond the
TV
application and not needed here.


I have been a ham radio operator for over 30 years and at one time held a
first class phone license that was good for the comercial radio repair.

When receiving the signal comes from the antenna it comes down on the
outside of the inner wire and the inside of the outer sheild. Unlike
Direct current which uses all the wire area, as the frequency goes up, the
signal only uses part of the area. That is a copper tube can carry just as
much signal as a solid wire the same diameter. Large coax (usually called
hardline) is often made this way. There is nothing useful on the outside of
the shield of the coax. In otherwords everything from the receiving
antenna is on the inside of the coax and coiling it up has no effect .

When transmiting it is possiable that some of the signal from the antenna
will couple or be introduced on the outside of the coax. This unwanted
signal will come back down the coax on the outside of the shield and can
cause problems with the transmitter and other electronics in the house. If
the coax is wound in a coil it may choke off this unwanted signal. The coil
is usually placed outside the house .