[Amps] Ferrite toroids

Carl km1h at jeremy.mv.com
Fri Aug 26 05:33:20 PDT 2011


Place a couple of turns on it and measure with a handheld LCR meter. Then 
use the standard formula to back into the AL value. Its not 100% but close 
enough since ferrites have a wide production tolerance.

AL (Mh/1000turns) = 1000000 x L / N squared
N is the number of turns you used

The more turns used the better the accuracy of some meters especially for 
powdered iron where I use 10 turns.

If you have a GDO placing a fixed cap across the coil works as long as its 
within its range.

Another which can be done with a GC receiver is to place the cap in a series 
trap arangement from antenna to ground and then try to find the suckout 
frequency. This can get tedious.

Configure as a parallel tuned ciruit, feed with a sig gen and look at a 
scope for a voltage peak.

Carl
KM1H


----- Original Message ----- 
From: "ZL2AAA" <zl2aaa at paradise.net.nz>
To: <amps at contesting.com>
Sent: Thursday, August 25, 2011 10:36 PM
Subject: [Amps] Ferrite toroids


> Can anyone tell me how to check the permeability of ferrite toroids.Morrie
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