Date: Thu, 6 Dec 2018 01:22:23 -0000
From: "David Robbins" <k1ttt@verizon.net>
To: <towertalk@contesting.com>
Subject: Re: [TowerTalk] Rain drops noise on Yagi (dipole)
<As far as preventing it, that can be difficult. Telrex tried adding rounded
balls to the ends of their elements for a while, but didn't round off corners
of t-match shorting straps or even the screws connecting the element sections
so did not solve the problem on <their antennas. I think most of the quads
that claim to be quite probably had insulated wire, which combined with
relatively few pointy things like screws or hose clamps would reduce or prevent
most corona. Dipping a driven element in liquid rubber might be <an
interesting experiment, but I would like to see a UV camera used on a Yagi
during a storm to see just where most of the corona is first, there may be
simpler solutions, or maybe not.
<David Robbins K1TTT
## Back in 1977-1981 I tried some experiments with general Electric ....
high voltage acrylic plastic, It came in a spay bomb. A local buddy had
arcing on the air variable on his gamma matched, shunt fed 50 ft tall tower,
he used on 160m..which was top loaded with a tri band, trapped yagi. The air
variable would arc across the stator and rotor plates, once power output exceed
aprx 80 watts. I completely un meshed the plates.... and doused it
with the GE spray. After it dried, cap was tweaked for the normal 1:1 swr.
No more arcing..even with 120 watts out. So far, so good. The fellows
amp did not have 160m...so I brought my..at the time, Dentron amp over, which
did have 160m.
I stuffed 1100 watts though the gamma matched tower, and zero arcing. I
was convinced I was onto something. Another buddy had a yaesu FL-2100 B
amp, with tiny spacing on the load cap. One rotor plate and one stator plate
touched
at one point of the rotation of the load cap... which of course, shorted out
the load cap.... which also happened to be on the band he used the most.
With almost zero spacing between plates, it was impossible to realign the
plates, if anything,
we made matters worse. So ran the load cap totally un-meshed and doused it
with the GE HV spray. After it dried, no more problems ! In fact, the
plates were STILL touching, right where load cap peaked for max output.
Ran like that for another 15 years that I am aware of. At that point I was
convinced the GE spray was a miracle cure.
## In 1980, I built a hb 5 el 10m yagi, all eles dc grounded to boom, and
gamma matched with a hb gamma match..consisting of polystyrene tubing, slid
over .5 inch OD al tubing. Extremely tight fit. Had to turn down the .5
inch tubing with a file,
while .5 inch tubing spinning away in my 500 rpm heavy duty drill. For
an experiment, all the els, which were 6061-T6 were cleaned with scouring
pads. Middle portion of each ele was a 12 ft length of 1.00 OD tubing.
Each tip was
.875 inch OD tubing. One SS hose clamp on each ele half. Dead simple. 26 ft
boom used, made of 2 inch OD tubing, with center 6 ft being double
walled. Since I had loads of GE spray left over, I doused all 5 els with
the GE spray.
Boom was not sprayed. Els stayed shiny until 1999. It was up 76 ft at
top of tower, back in 1980-1982. This was when I was up in northern BC.
Loads of snow, 8.5 ft per year, sometimes wet, but mostly dry powder. One
bad ice storm,
with .375 inch of ice on everything. Fair amount of wind from time to time.
10m Yagi was fixed on EU, no other yagis on the tower. That was a long time
ago, but I dont recall a single instance of rain / snow / wind static.
## I believe GE has discontinued the HV acrylic spray, as I cant find it on
their site. I did note, that in 1982, the 10m yagi came down, replaced by a
hb 4 el 20m yagi. Same dc grounded els, and similar gamma match. No GE
spray on the 20m eles,
as I had run out. The 20m yagi was also at top of the 76 ft tower..and also
fixed on EU. 20M yagi did have precipitation static from time to time, but
not often.
## If GE, or somebody else, makes a similar product, Id be interested, it has
a multitude of uses, as a cheap way of HV stand off. perhaps just the last
3-6 ft of each yagi ele needs to be doused with it, along with each end of
the boom, dunno.
Jim VE7RF
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