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Old July 14th 05, 06:23 PM
tjs
 
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"Hal Rosser" wrote in message
...


I think he was correct about the half-wave length of feedline:
according to the ARRL Antenna Book - 17th edition copyright 1994 -

page
24-12 in chapter 24, under the Heading "Special Cases" and under the
sub-heading "The Half-WaveLength Line", it pretty clearly states that
regardless of z, it will be the same on both ends of a half-wave line.

and
sections having such length can be added or removed without changing the
load Z. (as long as loss is negligible)

Also - You don't need to know the VF if you use a dip meter (or MFJ 259) -
And he would want the length to be half-wave so as to be able to ignore

the
characteristic impedence of the zip line and deal directly with the
impedence of the dipole directly.



Exactly

I also have a W6RCA type antenna up...80m dipole in the trees 25-50 feet,
fed by 98 feet of homemade 4" spaced ladder line, and ending outside the
shack wall with a way to add-in lengths of the feed line by 1 foot, 2 foot,
4 feet or 8 feet. This allows tuning the feedline onto any ham band almost
via harmonic relationship of the bands . You endup with a multiple halfwave
feedline and whatever swr the antenna runs shows up at the feedpoint (50
ferrite coax to ladder balun 1:1). Best antenna I have. Always better to
tune the feedline, and translate the antenna characteristic from the remote
locale to the shack wall. There is some loss I guess, but I cant detect it
or measure it, and I dont care because the antenna radiates and receives and
I get 59 reports.

Tim


 
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