The base insulator doesn't have to be expensive. Look for a used AM broadcast
When I put up my quarter-wave vertical for 160 back in 1980, 127' of Rohn 25, I
was able to purchase one that was sitting around in the junk room in the
transmitter building at a BC station. I paid them $100 for it, while at that
time a new one from Rohn was running $512 (1980 dollars). To-day a new one
runs well over $1000.
My second-hand one didn't fit the Rohn base section, since it had been used for
a larger tower, but it was easy to have an adaptor plate made. I found a hunk
of 5/8" steel plate at a scrap yard. I took it to a machine shop and had them
cut a round disc out from it, and drill 6 holes in the disc. 3 holes match
the mounting holes on the base insulator and the other 3 match the ones on the
tower base section. I had threads tapped into the holes, and bolted the
adaptor plate to the insulator, and then bolted that to the base of the tower.
It has been up for 28 years now. I think I paid a couple of dollars for the
piece of scrap steel, and the machine shop charged me $25 or $30 to make the
adaptor plate from it.
About 4 years ago at a local hamfest I found a base insulator that had been
taken out of service, that was designed for t he Rohn 25 tower. It was
probably identical to the $512 one that I didn't buy. I paid $25 for it. I
have in stored away now, just in case something ever happens to my original
base insulator. Pretty cheap insurance, I thought.
I have seen small tower base insulators at the Dayton flea market, something
that would fit a tower like the Rohn 25 or 45, go for $50 or less.
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