Topband: High voltage insulator

Raymond Benny rayn6vr at
Wed Jan 31 21:20:24 EST 2018

I need the experience and wisdom of this group.

I have am 80m vertical hanging off the side of my 160m vertical and share
the common radial system. The 160m vertical is 4" and 3" irrigation pipe,
72 ft tall with 4 - 30ft top hat wires and a loading coil at the base. The
80m vertical is up 68 ft and hangs from a 14" side arms and has its own
coax and loading coil. I have to short the 160m vertical to ground to
operate 80m. I run near 1500w output.

The problem is that the 80m insulator at the top shorts and arcs out over
time. I understand there is perhaps 6 - 10 KV at the top of the 1/4 wave
80m vertical. I can see it now arcing at night and my swr is jumping
between 1.5 to 2.0. My original insulator what just a small, abt 1" x 2"
white porcelain wire insulator that lasted for 2 - 3 years before it
cracked and shorted due to mechanical strains. My second was some sort of
composite insulate about 1" x 4" long that lasted abt a month before it
melted. My last insulator that is arcing, I think it is some sort of
porcelain insulator. Maybe its cracked too.

I am tilting down the vertical tmw to replace the insulator and want to get
some ideas as what to replace it with. I have both white and brown guy wire
insulators, about 1 - 1/2" dia by 3" long, or I'm wondering if a synthetic
material type might work the best. I have three pieces of synthetic rods,
about 3/4 to 1" dia. One is from the center insulator of a yagi driven
insulator from my junk box and about 1" dia by 8" long. I think its
fiberglass, but not sure. I also have from my junk box, one round stock
that might be Delron another and other might be Teflon or some other
synthetic material. I just placed the 3 pieces in the microwave with a cup
of water. After 2 minutes, all three were slightly warm. After a second 2
minutes hit, two of the synthetic types were very hot. The yagi dipole
center insulator which I think is fiberglass was still only slight hot.

So, what conclusions can I deduce? Which one might be best for my use? I'm
tending towards using one of the porcelain insulators.

Any thought or experiences? Are there more tests I can do on the synthetic
material rods?

Tnx for your thoughts and recommendations.

Near Prescott, AZ


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