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[TowerTalk] Inductor Design and Voltage Breakdown

To: towertalk reflector <towertalk@contesting.com>, amps@contesting.com
Subject: [TowerTalk] Inductor Design and Voltage Breakdown
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Thu, 30 Jul 2015 17:43:00 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
I'm designing a special 80M vertical for CQP (California QSO Party) county expeditions that can be self supporting for places where there are no trees. For it, I need a 20 uH loading coil. NEC tells me that running 600W, it will see about 1650V and about 3.5A. I'm concerned about voltage breakdown, so I've scoured the ARRL Handbook and the internet, and can't find any guidance. W8JI's webpage discusses the issues, but has no specific advice except to say that it can be a problem.

N6BV pointed me to a couple of ancient DOS programs that are good at predicting Q, inductance, stray C, and dissipation, but don't address voltage breakdown. And I had to find an old computer to run them on. Surely there must be good stuff around.

I'm tentatively thinking about 23 turns of #10 bare or enameled copper, 3-in diameter, about 5.3-in long. That works out to about 4.5 turns/in.

Suggestions?

73, Jim K9YC
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