Topband: Tower insulator thickness?

[Earl W Cunningham]

Jon, AA1K wrote:

"I'm planning on using some insulating material under BPC25 and BPC55
Rohn base plates (and around the pier pin in the center) so the towers
may be series-fed on 160.

Is 7/16-inch thick enough for this purpose?"
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Assuming the feedpoint impedance at the base of the tower is 36 ohms and
1500 watts is applied, that means the RF voltage developed between the
base of the tower and ground is 232.38 Vrms.

7/16" thick sounds like enough to me for that, but I would be more
concerned about the capacitance between the two base plates.

The 7/16" gap would probably break down with a lightning strike, but with
no other damage than burning a path through the insulating material.

73, de Earl, K6SE