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Old April 5th 05, 05:28 PM
Cecil Moore
 
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Wes Stewart wrote:
However, compare something like Andrew LDF4-50 to Wireman 554 and you
find that the "lossy" coax has a loss of 0.48 dB/100' @ 50 MHz and the
"low-loss" ladderline has a loss of 0.41 dB under the same conditions.


Hi Wes, let's say I'm trying to choose between the two.
Wireman 554 is about 25 cents/foot. How much did you say the
Andrew LDF4-50 costs? :-) (LMR-1700 is about 8 bucks/foot.)

Here's another way to look at things for multi-band non-
resonant antenna lengths. The feedpoint impedance for
that type antenna may vary from a low of about 50 ohms
to a high of about 7500 ohms. To minimize SWR for all
conditions, Z0 should equal the square root of those
two values or 612 ohms. Given 600 ohm open-wire line,
the SWR shouldn't go much above 13:1 for the open-wire
line but may go as high as 150:1 for the coax. I don't
know about you, but I would rather run with a maximum
SWR of 13:1 rather than a maximum SWR of 150:1.
--
73, Cecil http://www.qsl.net/w5dxp

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