Curious as why non resistor spark plugs aren't on the list of choices.
Easy to gap. Pt-Pt electrodes last forever (100k miles). There was a
ham mounting two on a Cu plate for ladder line, but that was many years ago.
Grant KZ1W
On 10/7/2019 2:21 PM, Jim Thomson wrote:
Date: Sun, 6 Oct 2019 19:08:17 -0500
From: Rob Atkinson <ranchorobbo@gmail.com>
To: topband@contesting.com
Subject: Re: Topband: spark gap construction ideas for 160m tower
<There are a number of ways of making a ball gap. but more important
<is arriving at the correct spacing for the gap.
<The way rain is handled is usually by positioning the balls one above
<the other so a water bridge doesn't form between the balls.
<Read this by Mark Persons:
https://www.radioworld.com/tech-and-gear/understanding-arc-gaps-for-am-systems
<Here's another treatment:
https://www.thebdr.net/articles/steel/twrs/LimitingStatic.pdf
<Kintronic sells them
https://www.kintronic.com/shop/tower-ball-gap/
<73
<Rob
<K5UJ
## a simple 1 megohm resistor across the base will drain static
buildup.
A 35-100 uh coil across the base will also drain static buildup.
Neither of the above will work with a direct lightning hit to top of
tower. A buddy used a helical hairpin across the base of his 100 ft
tall 160m vertical.... suspended between 2 trees...with T loading
capacity hats.
Helical hairpin also DC grounds the vert.
## I built a simple adjustable spark gap like Mark Persons describes
in the 1st url above. I used .25-20 brass machine screws...and
also mating brass lock nuts...and also brass acorn nuts..with their
domed heads. IF the acorn nuts get fried, replaced real easy.
## My hb spark gap is not for a vertical though. Its wired across
a 4 H Dahl, 127 lb choke... that I picked up across town. Its
a C-L-C filter network for a B+ supply. The C-L-C network is in
series with the B+... after the FWB assy. The choke itself is
isolated
from the chassis. The spark gap is just a safety precaution.... and
gapped
for like 300 volts.
## Identical adjustable spark gaps are wired across the vac load caps
on the hb linear amps. Gapped for a breakdown thats way less than the
hi pot test rating of the vac load cap. But higher than a max 2.5:1
swr across
the vac load cap... which is a PI net..so at a 50 ohm point. Amps
kick offline
with a 2:1 swr.
## Place a plastic cover above any outdoor spark gap. Any bugs will
be fried.
Jim VE7RF
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