[TowerTalk] Fair rite materials for choke baluns

[Jim Thomson]

Date: Tue, 5 Jul 2016 16:00:13 -0700
From: "Richard (Rick) Karlquist" <richard at karlquist.com>
To: Steve Hunt <steve at karinya.net>, towertalk at 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