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 <[email protected]>
To: [email protected]
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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