The article by Wes Stewart that I referenced earlier:
http://www.scribd.com/doc/7132619/Ladder-Line
was published in the ARRL Antenna Compendium Volume 6. It shows measured
losses for various commercial ladderlines when wet and dry. For example,
the loss of Wireman 551 increased from 0.33dB/100ft @ 50MHz to
5.8dB/100ft @ 50MHz; by contrast the loss of a home-made open-wire line
comprising #16 wire spaced 0.75" was 0.3dB and did not change when wet.
By the way, ARRL figures in the Antenna Book, and in their TLW software,
for ladderline grossly under-estimate the loss. If you do the basic RF
resistance calculations you'll get losses almost exactly double the
values they quote; I can't help think that whoever did those
calculations might have forgotten there are two wires :)
Steve G3TXQ
On 26/01/2012 18:20, Jim Brown wrote:
On 1/25/2012 10:54 PM, Rick - DJ0IP / NJ0IP wrote:
He found when the window-line gets wet from rain or snow, its impedance
changes a little and you have to re-tune your matchbox - but the efficiency
is still the same.
In one of the excellent ARRL Antenna Compendiums, Frank Witt published
the result of his research (including careful measurements) of loss in
open wire line and window line when it gets wet. Frank is a real
engineer. W1ZR is not -- he is a writer, and his writing in QST is full
of technical errors.
73, Jim K9YC
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