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Re: [Amps] Ferrite Core for 160M PI Output ?

Subject: Re: [Amps] Ferrite Core for 160M PI Output ?
From: Jim Brown <>
Date: Tue, 13 Jun 2017 09:59:10 -0700
List-post: <>
On Tue,6/13/2017 9:10 AM, JC wrote:
PI network loss is related with the Q of the inductor, you need material #2
or #6 ( better stability with temperature), #61 #77 are good for BALUN or
chokes and not good for inductors with high Q.

#77 is very lossy, not good for inductors to handle power, or have high Q. #61 is low loss below about 10 MHz, but loss increases above that frequency. Again, study the Fair-Rite catalog and my tutorial. Here's the tech data sheet for #61.

The first graph is a plot of mu' (classic mu) and mu'' (the loss component of impedance) vs frequency. Note that mu'' is off the graph low below 8 MHz, then rises rapidly so that it is quite lossy by 30 MHz.

Here's the data sheet for #77. Note that #77 is starting to get lossy at 100 kHz, and is as lossy at 1 MHz as #61 is at 30 MHz.

In general, a good common mode choke for noise suppression should be strongly resistive at the frequency of interest, ideally exhibiting a low Q resonance. #61 is useful as a core for common mode chokes above about 50 MHz.

73, Jim K9YC

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