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Re: [TowerTalk] Fair rite materials for choke baluns

To: "Richard (Rick) Karlquist" <richard@karlquist.com>, towertalk@contesting.com
Subject: Re: [TowerTalk] Fair rite materials for choke baluns
From: Steve Hunt <steve@karinya.net>
Date: Wed, 6 Jul 2016 08:31:43 +0100
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Note what I said about duty cycles!

Steve G3TXQ


On 06/07/2016 00:00, Richard (Rick) Karlquist wrote:
On 7/5/2016 11:00 AM, Steve Hunt wrote:
Do the maths on saturation - you'll find that core overheating occurs
well before saturation for the duty-cycles typical of Ham operation.

To quote Amidon: "Overheating of the core will usually take place long
before saturation in most applications above 100kHz."

Steve G3TXQ

This generalization is valid for cores with an air gap and
powdered iron cores (which essentially have a built in air gap).
It most definitely doesn't apply to closed gap ferrites,
such as toroids.  One dit can not only saturate them, but
actually magnetize them.  I have actually done this, accidentally,
when I tried to use a current transformer and the secondary
was unloaded.  It was something of a corner case since the
primary of a current transformer is only 1 "turn".

Rick N6RK
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