Holy colossal vertical dipole! You guys were serious. N6BT made his antenna
with pretty stout aluminum, and you found out why. It was a bear carrying it
from Houston to London to Malta, but worth the effort.
73, Keith NM5G
-----Original Message-----
From: TowerTalk <towertalk-bounces@contesting.com> On Behalf Of Jim Brown
Sent: Saturday, October 17, 2020 5:15 PM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Greyline Performance antennas
On 10/17/2020 1:24 PM, Kim Elmore wrote:
> Maybe I should have said "... making sure it has a good CM choke,"
> especially since you've taught us how to make them! Even if the feed
> is in the center (it could be if the transmission line is run up the
> bottom
> half) it still won't be balanced. A CM choke is always needed. I've
> become convinced that balanced antennas make analysis much easier
> (even
> possible) but that in the real world, there aren't any. I have no
> idea what the electrical length is for 6 m or even 10 m, so the low
> radiation-angle assumption might be invalid on those bands.
Here are slides for a talk I gave on the Pacificon Antenna Forum several years
ago on an 80M vertical dipole for our 7QP and CQP expeditions, based on N6BT's
design ideas. Yes, it does need a serious choke were the coax feeds up through
the tubing to the feedpoint.
http://k9yc.com/80M-FDVertical.pdf
Testing it in Glen's pasture showed it to significantly outperform an inverted
Vee with the center at 46 ft, but mechanical issues with the design caused us
to abandon it after modeling and building several alternative designs.
73, Jim K9YC
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