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[TowerTalk] Open Wire

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Subject: [TowerTalk] Open Wire
From: (Phil Clements)
Date: Tue, 16 Nov 1999 09:43:51 -0600
> Guys,
> My simple question about why one would use open wire in these days
> generated quite a bit of "noise" for open wire fans.
> There are two chief benefits from them:
> 1) Long runs like 1000' plus are not affordable with coax.
> (Like guys on 100'x100' lots care).  I can't imagine stringing 1000'
> of open wire line.  The supports must cost a fortune and the work
> involved seems overwhelming.

Not only the price, but the lossses.
My open wire line is about 500' long. It runs 380 feet horizontal from
the shack to  directly beneath the center insulator on my 133' dipole
160' in the air. I used 4 treated 4X4's , 12 ' long to support the horizontal
run, with the ladder line sandwiched between two pieces of plexiglass
screwed to the top of each 4X4. Cost was VERY reasonable, and the
losses are extremely low, even on the higher bands.

> 2) You can load an 80 meter dipole on all bands with it.  The same
> people pointing this out as a benefit admit to RF in the shack
> problems.

This is a "Gang Busters" antenna on 40m, as is it a full wave length long.
I built the tuner that is on the cover of the 1999 ARRL Handbook. The
system is perfectly balanced, and absolutely no RF in the shack at all.
I am using the "Textbook" Polyphaser grounding scheme here, and I am
sure this is the reason for success.

> It seems that one thing has been forgotten.  The line may be lossless.
> The tuner isn't.  Read QST and you will see that many of the
> commercial
> units available today have power losses of 30% or more.  The best unit
> quoted was a Johnson Matchbox.

The reason for the losses is that the components are usually too small.
I used a big roller coil (larger than the ARRL one) and vacuum variable
caps in my tuner. The combo of this and the ladder line is MUCH lower
loss than coax, even on the resonant frequency of 3505 khz.

> So you've substituted line loss for tuner loss.

The losses in a proper tuner design are negligable.

> Again where's the benefit?

Multi-band coverage (3.5-30 mhz) with very small losses.

> 73 de Brian/K3KO

Phil, K5PC
"The Dark Ages were caused by a Y1K problem"

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