Guys, this may be a stupid question, but if you use two parallel pieces of
(long) coax, wouldn't you have twice the loss. On the other hand, resistors
in parallel would mean half the loss. In any case, coax is lossy, heavy,
and expensive, so why would you use a long run of two coax cables?
Using short lengths to going through the wall is a good idea, but then why
would you need to tie the shields together at all and why ground them?
Sinisa?
Cheers,
Rick
-----Original Message-----
From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
On Behalf Of Darwin, Keith
Sent: Thursday, February 02, 2006 9:05 AM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] openwire feed OT
Ken (and others)
Oh, man, true confession time here :-). I've only done what I described
one time, years ago. I built a coax parallel feed line for a loop
antenna. The coax went from the back of the tuner, through the window
and all the way to the antenna. I connected the shields together at the
tuner end of the line and tied it to tuner ground. It worked fine. I
figured the same technique would be great for constructing a parallel
balanced line for use inside and near things that would upset the field.
Truth is I'm still not sure what to do with the shields :-)
I believe that the 2 pieces of coax can go their separate ways as long
as they start together and end together. The shield isolates the center
conductor preventing it from being affected by nearby stuff including
the other half of the parallel feed line.
I got the idea from an article in QST but don't really have the
engineering or physics data to truly explain how it all works.
In my personal case I feed RG-8x coax from the rig to the tuner which is
mounted 50 feet away. From the tuner I run RG-213 coax 30 feet to the
base of my 28' vert antenna. Doesn't work well on 80 but seems to work
well on 40, 30, 20, 17 & 15.
- Keith KD1E -
-----Original Message-----
From: tentec-bounces@contesting.com
[mailto:tentec-bounces@contesting.com] On Behalf Of K. Indart
Sent: Thursday, February 02, 2006 11:31 AM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] openwire feed OT
Keith,
I have two questions: Do you keep the two coax pieces separated by
the same spacing as your feed line,...or can you make ONE hole in the
wall/window and feed both coax through one hole ?
Does it matter which end of the shields get tied together; inside the
wall or outside the wall ?
Do you make the lengths of the coax JUST long enough to protrude
outside and inside of the wall or how long ?
Thanks, and it sounds like a very good idea.
73, Ken WA4RPH
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