Topband: Binocular Cores

[Roger Parsons via Topband]

Thanks Tom
I guess I really should have done that in the first place. They do appear to be the same mix as R ~ X at around 2 MHz in each case. I tested a few of each type and the variations in impedance were quite substantial, but didn't appear to be correlated to the DC ohmeter check. 

I guess the moral of the story is not to measure a parameter that the manufacturer doesn't specify!

73 RogerVE3ZI
     From: Tom W8JI <w8ji at w8ji.com>
 To: Roger Parsons <ve3zi at yahoo.com>; Topband <topband at contesting.com> 
 Sent: Monday, 1 June 2015, 11:31
 Subject: Re: Topband: Binocular Cores
   
You really need to do a single loop through the core windows and measure the 
impedance with some sort of analyzer. Even an MFJ259B with a short 
connection to the jack will work well for this.

If the resistance equals the reactance down somewhere around 2 MHz, it is 73 
material.

If R=X someplace much higher, you can be sure it is a different mix. The Q=1 
frequency, where R=X or where loss tangent crosses reactance, tells you the 
material better than anything else you can do.

That is how I quickly sort unknown cores.

73 Tom




----- Original Message ----- 
From: "Roger Parsons via Topband" <topband at contesting.com>
To: "Topband" <topband at contesting.com>
Sent: Monday, June 01, 2015 10:13 AM
Subject: Topband: Binocular Cores


>I have some binocular cores which I know are FairRite mix 73. I have others 
>which I thought were also mix 73. However, the first ones measure about 50k 
>Ohms with ohmeter prods onto their surface, whereas the others only measure 
>about 1k Ohm. I don't believe that that is a defined parameter, and am 
>aware that the test is not very scientific, but I am surprised to see such 
>a difference. Thoughts?
> 73 RogerVE3ZI
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