To: <topband@contesting.com>
Date: Fri, 27 Sep 1996 00:36:47
To: w2crs@kktv.com
From: Bill Hohnstein <k0ha@ltec.net>
Subject: Re: TopBand: The Hytower on 160M
At 09:42 AM 9/26/96 -0500, you wrote:
>
>SA>Doug, I've also had similar experiences with my hytowers...
>First the hytower has some mechanical weaknesses as shown:
>SA>fails - o-------
>SA> \/ \/ - Base insulators can arc over
...
>
>SA>73, Dick - K5QY
>
>Hi Dick,
>...I've never heard of the
>base insulators arcing over. They're at a low voltage point so I don't
>think that's a problem... I live in a very windy area and have
>never had any problems with the mechanical strength of the aluminum
>tubing section.
... You're right, there's no
>easy way to top load the Hytower that I know of.
>...I have considered adding an 8' section of tower to increase the total
>height to 60'. I think it would perform better on 160M, but am not
>sure I would be able to get it to resonate on other bands?
>73, Doug W2CRS
>
Hi Doug,
First some comments about your first email note:
I tried plexiglass at first, but the type that I tried didn't survive--
that clear stuff turned black (still arced). But that, combined with
your other changes, may provide the cure where mine didn't.
My lack of success with plexiglass made me more careful with the
Teflon. I added an extra half circle layer of Teflon tubing over
another piece of complete Teflon tubing (about the size of the original)
on the U-bolt side. I haven't had a bit of trouble since I made this
modification in 1980 (to an original size Hy-Tower).
I mention "original size" because in 1984 I added three tower sections
to it. I didn't want to change the base mounting method or position.
I purchased two of the lower-level Rohn BX tower sections and one of
the mid-level sections. I cut off the smaller ends of these pieces and
spliced them on to the same size original sections. The splices were
made so that some of the cross braces went across the splice. I guyed
the "high-Hy-Tower" near the top of the tower. There have been no
mechanical problems since (and no problems with the Teflon insulator on
the high-Hy-Tower either).
I don't know if they have changed insulators since, but my Hy-Gain
stub insulators only seemed to last 2 or 3 years before the sun would
cause them to crack then break. I had previously taken those stubs
off since I hadn't intended to use the antenna on 15 or 10 meters.
Because of this, I didn't even think about making the high-Hy-Tower
work there. The complete height of the new tower/tubing was then
electrically 5/8 wave for 40 meters (part of "the plan"). I built
a LC circuit at the tower base to match it to the coax. Just a series
doorknob capacitor at the tower's base provided an excellent match and
bandwidth on 80/75 meters. I added a parallel quarter-wave stub wire
for 30 meters (held off by 4' fiberglass electric fence posts). It was
mounted with the top of the stub near the top of the tower. It has
worked well on 30 meters though I haven't been on there as much as I
should be.
This high-Hy-Tower has never really be used by itself. It was used
mostly as the driven element for my 160/80/40 meter six element
parasitic vertical array. About 1985 I center loaded the high-Hy-tower
for 160 meters--just before the tubing started I placed an inductor.
It didn't lower the resonant frequency to the bottom of 160--I used a
much smaller number of turns at the base to tune to the part of the
band desired. It's hard to rate the benefits of this center loading.
I didn't do any reliable "number tests." A/B tests would mean
climbing the tower to make the change... For that matter, changing
from 160 meters to any other band would require climbing the tower...
Contrary to K5QY's mechanical complaints, I climbed the tower on some
awfully windy days (during contests) to change bands and never had
any physical problems with the tower.
In 1991 the world changed! I moved to some flat farming land and
started over on antennas. The high-Hy-Tower went back up early, in
much the same manner (though not with parasitics at first). With more
wind in the country I decided to guy it at two levels. The 160 center
load was removed since a new 160 meter driven element was planned.
I'm just now working to add parasitics to the high-Hy-Tower. It'll
be an 9 element parasitic array. 4 elements will be active towards
Europe on 80, with 6 elements active towards Europe on 40. I'll also
be retweaking my 4 element parasitic vertical array for 160 (3 elements
active towards Europe [or the South Pacific]).
This is getting to be a novel--so, back to your note... I've mentioned
never having the mechanical problems that K5QY spoke of. There's been
some thick freezing rain along with some pretty potent winds that have
failed to damage it. A tornado that damaged a neighbor's roof didn't
faze it...
I agree that there shouldn't (and haven't) been any problems with the
base insulator arcing over. I did decide to take advantage of my
opportunity and replace those insulators when I moved here. I decided
that a replacement after 13 years would make me feel better if
nothing else...
Good luck on your antenna work and amp repair.
73,
Bill K0HA
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