[TowerTalk] [RFI] Snap-on Ferrites

[Jim Thomson]

Date: Mon, 19 Jun 2017 12:17:31 -0400
From: kc4pe <kc4pe at bellsouth.net>
To: towertalk at contesting.com
Subject: Re: [TowerTalk] [RFI] Snap-on Ferrites


’On 6/19/2017 10:11 AM, Chris wrote:

>> And what about the Ham at the show that was selling  ferrite snap ons (small) with a blue and red labels with bold arrows printed on the black label? What coulkd the arrow mean??
No idea what or who you are referring to, can't comment. If there is no 
manufacturer listed with the mix, it is impossible to tell what you've got.
/*Right it was strange, but he had documentation that it was Mix 31 
...had single pass through with 1/4 - 5/16 pass ....Some had a red 
label, some had a blue label, but all had a very bold black arrow .. 
*//*Why would you ever orientate a block of ferrite?

  Thanks Again..*/
>> -Bill .. KC4PE
>>

##  Unlike the colour coded powder iron toroids,  ferrite is not colour coded. 
One simple test to do on unknown mixes is to wind a few turns of wire on the toroid, then
measure its inductance  in uh with a digital  LCR meter.  Then compare against a known ferrite mix
using the same wire, and same number of turns..and same dimensioned core. 
LCR meters typ operate at low freqs, like1 khz or 100 khz.   If you use a bead balun, same thing, 
you can measure the uh between the extreme ends of the bead balun..and tell at a glance the difference
between a bead balun made from type 77-31-43-61   instantly.   Its blatantly obvious.  

##  If u wrap XXX  turns of wire onto say a type 31,   2.4 inch OD core.... measure the uh, then  repeat
the same test on several other type 31,   2.4 inch cores, you will measure variances in uh between them.
This is due to manufacturing tolerances...this is normal. 

Jim   VE7RF