[TenTec] SLIGHTLY OT

[Steve Hunt]

On 08/04/2011 19:29, Dr. Gerald N. Johnson wrote:
> A quarter wave center fed wire has low radiation resistance and is very
> capacitive. Bad phase angle.

Correct - an EZNEC model of his antenna puts the feedpoint impedance at 
around 11-j930 Ohms

> You run that through a 600 ohm line about a
> quarter wave long, converts low R to high R and C to L.

No, that's wrong. A quarter wavelength of 600 Ohm line transforms 
11-j930 to 4.5+j386.
His 110ft of open wire will transform 11-j930 to around 7+j290

> So your balun
> sees high impedance that may be causing core saturation (for sure in a
> voltage balun) and you see high Z at the tuner.

A true 1:1 Guanella balun will not saturate because of a High Z 
differential load. The core flux is driven by *Common-Mode* current, not 
by differential-mode voltage.

Perhaps surprisingly the 10ft of LMR600 then has a major effect - 
transforming 7+j290 to 206+j1573

If you look at the L-network needed to match that impedance to 50 Ohms 
it requires much more inductance than the 238B is capable of. I wonder 
if your tuner is at max L as well as being at max C?

73,
Steve G3TXQ