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
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