George (K8GG) & Marijke Guerin
gmguerin at voyager.net
Sun Mar 5 07:53:06 EST 2006
Here is my two cents worth:
>> W8JI wrote:
>> > I'd never make the L 3/8th wave.
>> > I'd make the inverted L a 1/4 wl.
If one uses a 1/4 wl inverted-L, then it can be easly matched by an UnUn.
Examples can be found at:
The UnUn labeled:
W2FMI-1.78:1-HMMU50 (multi-match UNUN)
has lots of input and output taps and can match impedances from 3.13 up to
Keeping the 160 meter inverted-L connected to ground through the windings
prevents it from being a resonant half wave floating wire on 80 when using
the 80 meter vertical nearby.
Tom G3OLB wrote:
> The advantage with making it a little longer than 1/4 wl is that it tunes
> with a simple series C. What's your recommended way of matching a true 1/4
> wl to 50 ohm coax?
The problem here is that to get to about 50 ohms (tuning out the inductive
reactance with a vacuum capacitor of 400 - 450 pfd), one needs a 5/16 wl
inverted-L (160 ft length) 80+ feet up and 80- feet out over 3000+ feet of
radials to get a good ground. It works great if you have the space, time
and energy to do it right. Going to a lower 3/8 wl configuration makes for
lots of horizontally polarized radiation from the about 1/4 wl horizontal
part of the wire and over 1/2 the energy goes nearly straight up... not good
in my opinion.
GL 73 George K8GG
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