On Wed, 2008-05-07 at 04:17 -0700, Jim WA9YSD wrote:
>
> Thanks Doc Gerald. That solved a few mysteries for me.
>
> Now I
> know why my vertical worked well on the roof of the house because I put
> a voltage balun at the feed point. It was luck because thats all what
> was made in those years.
>
> So now if I want to put up my 80M
> folded dipole as an inverted vee again I need to find a 4:1 Current
> balun and put it at the end of my short ladder line. The inverted vee
> folded dipole has a center impedance of 185 ohms. Ladder line stays
> out side, and I run coax the rest of the way.
>
> An
> isolator/current balun would stop the RF current coming into the shack
> when placed just before the Lightning protection out side.
If you already have a balun at the feed point, this balun would keep RF
from coming into the shack that the outside of the coax picked up
working as a slant or vertical wire. There might be slight improvements
in noise and TVI and might not. It won't have enough impedance or
bandwidth to keep much of the lightning out. Cutting a kiloamp or two by
90% is still a damaging current.
>
> If your not in this type of situation then the next best place is at the out
> put of the antenna tuner. Attach a good RF ground directly to the tuner.
>
I'm not a fan of tuning through a balun. I've found situations where
after tuning removing the antenna had no effect on the match on the
input side of the tuner. So the tuner had resonated the balun (voltage
balun in that case) and was dumping all the transmitter power into the
balun (save the tuner losses).
> Do I have it correct?
>
> Keep The Faith, Jim K9TF/WA9YSD
>
>
73, Jerry, K0CQ
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