Date: Tue, 5 Jul 2016 16:00:13 -0700
From: "Richard (Rick) Karlquist" <richard@karlquist.com>
To: Steve Hunt <steve@karinya.net>, towertalk@contesting.com
Subject: Re: [TowerTalk] Fair rite materials for choke baluns
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
## So duty cycle does play into all this. As in it could be possible
to saturate the cores...without heating them up, as in via low duty cycle
pulse tuning
an amplifier with real low duty cycles, or perhaps un-processed ssb etc.
## Ok, what happens when cores ARE saturated... but with minimal heating
involved ? I cant see the SWR changing on a CMC.... but I can see the
CMC ceasing to work, and CM currents increasing a bunch. IOW, it
might be like the CMC isnt even there. Once saturated, will the CMC
function again, if power is reduced, or say after a period of time.
Jim VE7RF
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