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[Amps] What to buy? - ferrites and powdered iron

Subject: [Amps] What to buy? - ferrites and powdered iron
From: "John Lyles" <>
Date: Fri, 4 Feb 2011 13:50:54 -0700
List-post: <">>
The consensus read here says "no" to ferrite in high power RF amplification. 
in proton synchrotron particle accelerators, ferrite is used nearly universally 
as part of the tuned
circuit, in the resonators used to develop very high RF voltages. Fair Rite, 
Amidon don't offer 
any product for this use, but Philips/Ferroxcube and a few others do. 8C12, 
4B3, and 4M2 have been used 
up to the limit of flux density from 0.5 to 20 MHz. The cores are huge, ~0.5 
meter diameter. DC bias is 
applied to vary the mu and allow the resonators to be tuned to track the proton 
or heavy ions as they speed up. 
I played with this stuff about 10 years ago for a project that was cancelled, 
including building a test driven by 8877 at 5 MHz.
 I may have a paper and poster on the topic that I can share on request. In 
this case, the variability of mu with bias and flux is used to benefit. Iron 
powder toroids weren't used to do this. 

> Message: 6
> Date: Thu, 3 Feb 2011 04:02:13 -0800
> From: "Jim Thomson" <>
> Subject: [Amps] What to buy?

> Date: Mon, 31 Jan 2011 10:52:57 -0500
> From: "Carl" <>
> Subject: Re: [Amps]To: What to buy?
> Hmmm, ferrite has never been recommended for RF tank circuits that Im aware 
> of. Ferrite is fine in receiver and other low level applications mostly at 
> low frequencies.
> Good amplifier engineering has used powdered iron in various mixes, 
> generally from Micrometals in North America.The #2 mix is the usual choice 
> in amps for 160-80M and has been in use since the late 70's.
> There are huge differences between the 2 materials in regards to losses and 
> temperature stability.
> Carl
> KM1H
> ----- Original Message ----- 
> From: "Jim Brown" <>
> >> How are things different in a transmitter's resonant circuits?  First,
> > we want to minimize loss, so we (should) use low loss cores (like
> > Fair-Rite #61 or #67). These are NiZn cores, and have much lower mu than
> > those designed for RFI suppression (like #31 and #43).
> >
> > Inductors wound on #61 or #67 can have Qs on the order of 10 or more,
> > and are typically self-resonant a bit above HF. 
> > Note also that my work has focused on ferrite materials, NOT powdered 
> > iron.
> >
> > 73, Jim Brown K9YC
> ###  Ferrite  would not last more than 30 x seconds in any tank circuit, in
> any HF amplifier.  Type #2 mix [ red cores]  powdered iron cores are what is
> normally used.  Beware that there are TWO types of T-225 cores... lableled
> 225-2A   and  225-2B.    The A version is only 1/2" thick.  The B version is 
> 1" thick.
> Jim   VE7RF  

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