What you relate are classic ground proximity symptoms.
In the case of 40 meters you tuned the length of the 40 meter wire at the lower
height. When you raised the capacity to ground from it changed. My experience
with the Gap is that the 40 meter wire has to be readjusted with a change in
height.
In the case of 80 meters, the reason that the Gap was broader banded was because
ground absorption is essentially broadband. In free space, an antenna as short
as the Gap on 80 meters is going to have a very narrow low swr range around the
matching point. Can't be fixed, just physics.
You could achieve broadbandedness by putting a dummy load in series with the
feedline. 80 meters will broaden out very nicely. :You were using the ground as
a like dummy load.
On 80 using the Gap, you have to pick your 50 kHz window, or use a tuner (low
power only). They will send you a cap for whatever freq you want. I got one for
the low end (3.5 MHz). The one they normally send for CW is for 3.6 MHz
Your 10 and 15 meter results told the truth.
- - . . . . . . - - . . . . - - . . - . .
73, Guy
k2av@contesting.com
Apex, NC, USA
----- Original Message -----
From: Greg Gobleman <k9zm@frontiernet.net>
To: 'Tower Reflector' <towertalk@contesting.com>
Sent: Monday, October 11, 1999 8:16 AM
Subject: Re: [TowerTalk] GAP Titan
>
> The ground screen very definitely helps. Another way to help is to raise
the
> antenna, at least 10 feet from the bottom to the ground
I had my Titan mounted at 12' and at 2'. When at 12' this helped the
receive on 10m and 15m. It also shifted the usable portion of 40 and 80m by
a considerable amount and narrowed that usable portion. As I wanted good
40m performance I tried the low mounting and 40 and 80m improved to specs.
Not that this antenna was a great performer. Sometimes on 40m it worked
super and I can recall many times when I could not make myself be heard. On
80m I did work EU at their sunrise but this thing seemed to be a good dummy
load. It seemed to perform best on 20, 30 & 40m. We are talking bottom of
the sunspot cycle to last spring. The counterpoise has 2 adjustments, one
for 40m and the other for 10m, so I wouldn't remove it as has been suggested
by some. I never did lay down a radial field or ground screen under the
antenna, but not attached to it. I always did wonder if it would help, but
couldn't get any encouragement from anyone that it might. I see from a few
messages that I should have tried it.
73
Greg K9ZM
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