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KG6BAJ > NWSGRP 29.09.09 20:26l 57 Lines 2295 Bytes #999 (0) @ WW
BID : 12063_N1OES
Read: GUEST
Subj: Re: Open wire feedline
Path: DB0FHN<DB0MRW<DB0ERF<OK0NAG<OK0PPL<DB0RES<DK0WUE<7M3TJZ<XE1FH<AA6HF<
KG6BAJ<KG6BAJ
Sent: 090929/0800Z @:KG6BAJ.#NCA.CA.USA.NOAM #:12063 [Grass Valley] InterGate $
** NEWSGROUP: rec.radio.amateur.antenna
** FROM : Tim Shoppa <shoppa@trailing-edge.com>
On Sep 28, 2:44=A0pm, Ron Walters <w4...@numail.org> wrote:
> I am feeding a 80 meter center feed with open wire, about 100ft feed-line=
.
>
> Due to some new construction work that is going to start on the back of
> our home this week I am forced to move the feed-line.
>
> The original installation had about 50 ft vertical from the center of
> the dipole and then across and under a raised wood porch and then up to
> a second floor shack.
>
> The porch is going and a new covered screened porch is replacing it.
>
> I have three choices during construction, they are:
>
> 1. =A0Leave the 100' feed-line coiled out in the yard and not operate.
> (Not a great idea)
>
> 2. =A0Cut the feed line down to around 50' which would be temporary but
> then I would have to splice it later after construction.
>
> 3. =A0Coil about 40' near the 4:1 balun, however I am concerned that the
> coiled feed line will act a one big inductor and change and or
> significantly reduce the antenna efficiency.
>
> #3 is the easiest but I am worried about open wire feed-line coiled,
> thoughts please!
#3 is less than optimal unless you actually want a big coiled piece of
feedline as part of your antenna setup. There are some folks that have
big coils of feedline just for impedance transformation purposes, I
always think it's odd but that's what they like.
Splicing parallel feedline (whether it be homebrew ladder line or
commercial window line) is not a big deal. The copper plated steel
stuff is hard to bend with your bare hands but is easy enough with
pliers. Splicing it with solder, and without a good mechanical twisted
splice, will mean that after some flexing it will be break at the
splice point. But make a good mechanical splice like in the handbook
and you'll do fine.
But if you don't really need that 50 feet of feedline then why keep
it? Straightest shot to the antenna will always be superior unless you
want that extra 50 feet for impedance transformation or something
else. Sounds like in most circumstances it'll be a win-win to keep the
shorter more direct routing.
Tim.
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