I just have one final comment on this. Even though the feedline losses
at HF are all mostly from I squared R loss, it just happens to turn out
for other technical reasons that the more lossy the dielectric is, the
more lossy the feedline is. I can find no exception to this.
So if one wanted to design a feedline with as low a loss as possible for
other given reasons, using the lowest loss dielectric would give the
best results.
Carl Moreschi N4PY
121 Little Bell Dr.
Hays, NC 28635
www.n4py.com
On 1/26/2012 2:17 PM, Steve Hunt wrote:
> 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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