[Antennas] spencer dipole from Mccoy's book

2002年1月03日 11:04:25 -0800

At 11:00 AM 1/3/2002 -0500, you wrote:
>I was under the impression that ladder line could not pass near metal
>objects. The feedpoint will likely be very close to my 35 foot tower, and
>I have aluminum facia and gutters all around the house. Therefore the
>thought of shielded balanced line.

You are correct, but the spacing distance required from conductive surfaces 
is less than many may be aware. The rule of thumb is 2� to 3 times the 
center to center spacing of the parallel conductors. In other words using 
the popular 450-Ohm window line the distance between the conductors is 
eight tenths of an inch would require that it come no closer to a 
conductive surface that two to three inches. That's not hard to do.
One caution here, wet window line has higher losses than the old fashion 
open ladder line. Wes Stewart, W7WS wrote a fine paper on this subject 
which was published in the ARRL Antenna Compendium Volume 6. You may wish 
to consult that before proceeding.
73
Danny, K6MHE