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Old April 23rd 04, 05:41 PM
Bob
 
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Default Ladder line question ????

I have the 50 foot tower, it is right outside the shack window, so will be
drilling the two small holes in the sill, then fishing through approximately
12" or 18" then replace the spacers to keep the distance between the leads
constant. That leaves the remaining 98 feet outside of which I need a
distance of approx 35 or 40 feet of the ladder line to reach my center fed
80m or two wires 66feet each leg. What are my options with the left over 50
feet (approx) of ladder line? Coil it up? Cut it? And what are the rules
about keeping the ladder line away from the tower and steal guy wires that
are not insulated? I only want to do this once now and first time using the
ladder line, all suggestions appreciated, thanks.....


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Old April 24th 04, 01:33 AM
K9SQG
 
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Well, all I can do is relate my experiences, which don't totally agree with
theory.

The spacing between the wires entering the home is not critical. I have two
feedthroughs for my open wire line, 450 ohm, where the spacing goes out to
about 8" for 3 feet. I could measure NO change in the SWR as a result of that
spacing for that distance on my SWR meters (Drake W4, Autek WM-1, and Nye
Viking MBVA).

Further, in a previous location, I noticed no change in SWR when the ladder
line was laid on top of a flourescent light fixture for 2 feet.

In general, it is best to cut off that excess feedline, but, in some cases
adding a little back in can help with problem SWRs on some bands. With a
reasonable antenna tuner (Johnson Matchbox, double balanced tuner, link coupled
tuner, etc. ) you should still be able to tune it in most cases.

Finally, I've made 90 deg , sharp bends with the ladder line and could detect
no change in SWR.

I always listen to theory, wives tales, but give some credibility to acutal
measurements as well.

73s,

Evan
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Old April 24th 04, 04:54 AM
'Doc
 
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Bob,
Keeping the spacing of the ladder line going through a sill
is sort of a waste of time. Make the spacing whatever is
convenient, since what is between the conductors will change
the impedance from whatever it normally is, anyway. As long as
it isn't for a very long stretch of feed line, it isn't going
to make much difference.
Keeping the ladder line away from metal objects about 3 or
4 times the width of the ladder line (what's that, about 4 to
6 inches give or take a little?).
Coiling up ladder line isn't a very good idea. If you have
any extra, cut it off and save it for later. The length of the
feed line can make a difference in the tuner's ability to get a
match at some frequencies. So, try it with just enough to reach
and if that is a problem, add a little more. You will
eventually
find a 'right' length for the particular bands you want to use
(if
you use the antenna on more than one band).
Playing with antennas is almost never a "do it one time and
forget
it" kinda thing. That's half the 'fun' of playing with
antennas...
'Doc
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