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KG6BAJ > NWSGRP 29.09.09 03:22l 34 Lines 1186 Bytes #999 (0) @ WW
BID : 12048_N1OES
Read: GUEST
Subj: Re: Open wire feedline
Path: DB0FHN<DB0MRW<DB0ERF<OK0NAG<IK6ZDE<DK0WUE<DB0RES<ON0AR<N9ZZK<KG6BAJ<
KG6BAJ
Sent: 090928/1600Z @:KG6BAJ.#NCA.CA.USA.NOAM #:12048 [Grass Valley] InterGate $
** NEWSGROUP: rec.radio.amateur.antenna
** FROM : Owen Duffy <none@no.where>
Ron Walters <w4lde@numail.org> wrote in
news:4ac103d3$0$11071$4c5efa9e@news.corp.moreusenet.net:
...
> 3. Coil 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!
If you coil the transmission line so that the distance between turns is
much greater than the distance between the conductors, you will not
significantly alter its differential mode operation (which is its main
purpose in most antenna systems).
You will alter the common mode current distribution, probably for the
better. Remember that some folk use common mode chokes in systems using
open wire feeder, and you will create a common mode choke by coiling the
line as I described.
You could suspend the coil on a roughly horizontal span of nylon fishing
line to support and space the turns.
Owen
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