Copyright © 2002-2019 by Harold Melton, KV5R. All Rights Reserved. Rev. 02/19/19.
Entry: Feed-Throughs and Lightening Arrestors
How to make your own spark-gap shunt (“lightning impulse arrestor”), waterproof ladder-line feed-through, and quick-disconnect for (hopefully) improved lightning safety, using common hardware. Or, how to possibly avoid the “billion-amp arc in the shack” scenario.
Disclaimer: All disclaimers apply. No guarantees. I am not an engineer nor expert in the field of lightening protection. I assume absolutely no liability for your use of this material. These ideas have not been tested. Use at your own risk! The actual effectiveness of these measures cannot be quantified. Lightning is dangerous, destructive, deadly, and unpredictable, due to rapid release of incredible power, and extremely wide range of variability.
My HF antenna is a 160 meter dipole, fed with 14-gauge windowed ladder-line. This arrangement should make a nice lightning collector, so I took special precautions on the entry path of the ladder-line.
In figure 1, notice the PVC standoff (one of two), made of half-inch PVC, about six inches long, attached to the trailer with aluminum angle. The ladder-line proceeds down to the arc-shunt assembly, which is mounted directly on the ground rod. It then proceeds up to brass feed-through assemblies (Fig. 2). Once inside, it plugs into the tuner with banana jacks (Fig. 3), for quick disconnection.
The ladder-line is kept separate from all the other cables, which enter via a 1½-inch PVC nipple and coupling (inside) through the floor. The coupling is packed with paper towels (and a little boric acid powder) to keep out bugs. The arrangement provides a good seal that can be easily removed and replaced to allow passage of PL-259s intact.
In the spring of 2018 I went QRO, and put up a heavy-duty 80-meter doublet, fed with 4-inch open-line. I made three different entrances: (1) Wires through tubings through the wall; (2) twin coaxes through the wall; and finally, balun outside and coax through a bulkhead fitting in the wall. All worked well, but I like the last one best, for several reasons.
Please see 80-Meter Doublet in the 2018 section. Lots of pictures!