[Elecraft] Balun Questions

[Wes (N7WS)]

If you're driving a 50 ohm load, then the cable wound around the core is just an 
extension of the transmission line and has no impedance modifying effects.

The significant parameter is the common mode (CM) impedance. G3TXQ discusses a 
way to measure it here: http://www.karinya.net/g3txq/chokes/#measurement

You can back into whether the CM is high enough by terminating each output with 
a resistive load to ground and measuring the two output voltages and phases with 
something like an HP8405 Vector Voltmeter.  Walt Maxwell, W2DU, discussed this 
in his book, "Reflections II" (p, 21-8 thru 21-10)

On 2/6/2016 11:06 AM, 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?
>
> It appears to function when I put it inline.  The KAT100 seems happy.  It produces a decent match on 40-10m using the 44' long rotating dipole at ~37' fed with 450 ohm twin lead.  I have no idea how efficient it might be, of course, if at all.
>
> I still don't hear the VP8 much above the noise. :>(
>
> 73 de W6OGC Jim Allen
>
> Sent from my iPad
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