From: Earl W Cunningham <k6se@juno.com>
To: <towertalk@contesting.com>
Date: Tuesday, July 28, 1998 10:39 AM
Subject: Re: TopBand: good commercial 160 ant?
>Modeling software shows that a 45-foot vertical with four "radials" each
>41 feet long connected at the top and extended horizontally will resonate
>at 1830 kHz. The feedpoint resistance will be about 10.25 ohms, so a 1:4
>unun will give a close match to 50-ohm coax.
>
OK, so I just loaded 10 new Duracell batteries in my 259B, and out
to the base of the TL160 to measure the resistance and reactance.
Gladiator TL160 is 38 feet long, with base up about 12 feet, so
top is up about 50 feet high above the ground. My top hat wires
are about 70 feet long, I think I recall; the down sloping elevated
radials are about 130 feet long, best I recall. Anyway, they go
a long way into the wild country out back. I must do a lot of limb
and vine clearing to get this thing set back up as I want it; see
below:
Found that the jungle vines just love my twin lead radial wires; vines
all over them, hi! So it is once again machete time. Except will
have to pull the vine crawlers out of the "windows" in the line.
Anyway, appears the vines have pulled my resonance down to
1.758, where I measured, at the lowest vswr I could find to the
50 ohm meter:
R= 43 ohms; X= 34 ohms vswr= 2.0:1
and up where I used to have resonance:
1.830 MHz
R=17 ohms X=36 ohms vswr= 3.6:1
Of course, with my XMatch Classic Low Bander tuner, I have
no trouble loading up at 1.830.
So, thought I would also check out my 20 meter Gladiator, as
it is completely above the vines, and of course, no top hat
wires, but does have the down sloping elevated radials
wires, four of them, same as the TL160.
Resonance is now at 13.826, at least that is where X=0 ohms,
guess I better shorten the aluminum sections a bit:
At 13.826 MHz,
R= 41 ohms, X= 0 ohms, vswr= 1.1:1
At 14.015,
R= 47 ohms, X= 6 ohms, vswr= 1.1:1
At 14.100,
R= 49 ohms, X= 9 ohms, vswr=1.1:1
At 14195,
R= 53 ohms, X=11 ohms, vswr= 1.2:1.
That is closer to the numbers and bandwidth percentages
I had had pre-vines with the TL160.
Wish the tropical sun were not so hot now. Summer has
at last come to Kauai, so will have to do my vine trimming
early mornings and late evenings, hi.
Bob Myers, the designer and builder of the Gladiators does
have an "unun" at the base, in a wx protected box of the
Gladiators. Different one for each band, I guess. One
BIG ferrite toroid in there, anyway!
Sure do have fun with these Gladiators; I have only 7 of them,
and a couple more coming, hi!
Unfortunately, have yet to recv my back ordered MFJ precision
step attenuator. Still want to do some more beacon tests, and,
maybe some more radial wire count tests. Think I will go back
wards first; drop from four to only two radial elevated wires on
the 20 meter unit to see what that does to the beacon signals
from around the globe on 14100.
Isn't this a great hobby/!! Will be happy when the dust has
cleared from the FCC/restructure issue.
73, Jim, KH7M
On the Garden Island of Kauai
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