[Elecraft] Balun Questions

[Mel Farrer]

Let's do some basic thinking. The balun you made with a ferrite torroid and a length of coax is a straight piece of coax with the two ends supposedly isolated for CMC common mode current., right?  How do you make a simple measurement on the lowest frequency?  Expensive equipment, right?  Well, what is the next best way to determine the isolation at RF, Hummm.  If I measure the inductance across the two ends of the balun that is shield to shied to make it easy,  the ferrite increases the inductance of the many turns through the core, right?   If you take the number in uH and put it into the: ( Xl= 6.28*F(HZ)*inductance(H)), formula you get an equivalent reactance in ohms at the frequency of interest.  Yes, I know there are other factors, but it gives you a figure of merit against any other current choke baluns, or other designs you would like to try. Remember More is better.    Funnnnnn.
Mel, K6KBE


      From: Richard Fjeld <rpfjeld at outlook.com>
 To: elecraft at mailman.qth.net 
 Sent: Monday, February 8, 2016 12:57 PM
 Subject: Re: [Elecraft] Balun Questions
   
This doesn't answer your details, but what I did to test the one I made 
was simply to compare it to the balun in my manual roller inductor 
tuner. I used a short coax jumper between the tuner and the homebrew balun.

Dick, n0ce

On 2/6/2016 12:06 PM, Jim Allen wrote:
> Ok, so this morning, I went out to the shack and whipped up a balun, from a G3TXQ design I found on the website of W5DXP.com.  It is coax wrapped around a ferrite core, with appropriate connectors in a plastic weathertight box.  I used RG8X coax, a 2.4" core, not sure exactly what mix, and 11 turns.
>
> How do I test this device to get its properties, impedance at various frequencies, etc?
>
>

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