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Topband: Flattop with 450 Ohm feeders

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Subject: Topband: Flattop with 450 Ohm feeders
From: sire at (Steve Ireland)
Date: Thu Aug 14 05:25:45 2003
At 09:11 PM 12/08/2003 +0600, you wrote:

W3PT said:
>I have put up an antenna for my daughter-in-law KB3AGR that is ( 130 feet,
>as much wire as I could stretch between two trees) feed with  50 feet 450
>Ohm ladder line to a balun under the eve of the house. This is a current
>balun sold by Radio Works and is supposed to have a very short coax run from
>it to the radio. That run is 25 feet of LMR400.
>I was trying to get this to resonate on 160 until I found out that her
>Kenwood 690AT does not tune 160. It tunes all the other bands great.

VK6VZ replied:

Hi Bob

You might like to try simply adding 66' of wire at each end of the dipole,
and just slope them down to a couple of short poles (say 8' high, to keep
the high voltage ends out of the reach of hands).  Get rid of the current
balun and feed the 450 ohm line directly into a Transmatch or similar
old-style ATU (although a proper balanced parallel-tuned ATU would be ideal).

This sort-of-inverted U-shaped antenna worked my first 100 countries on
160, WAS (and K2WH!), plus being a really good DX performer on 80 and 40m.

I used to change at the roof-line from 600 ohm type open wire feeder to
high-quality 300 ohm slotted ribbon, running the ribbon under the roof
tiles and down inside the wall cavity into the shack, where the Transmatch
ATU was situated. It used to work like a charm - on all bands from 160 to 10m.

It is a five-minute job for an electrician to run the ribbon through the
wall cavity and drill a hole in the shack wall as an exit point (and they
will even put a nice looking cover over the hole for you!)

Vy 73

Steve, VK6VZ

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