[CQ-Contest] Feedline length
Tom Rauch
W8JI at contesting.com
Wed Oct 10 12:53:49 EDT 2001
> > Using (2n+1)*L/4 would isolate dipole half connected to coax shield
> > from the ground making balun redundant.
>
> >From my own bitter experience, that would be completely
> unreliable way of avoiding common-mode currents.
>
> 73,
>
> Sinisa VA3TTN
The reason it is unreliable, is because:
1.) We often have no idea what the shack ground is like electrically
2.) The feedline is usually tapped to other cables or towers, or
routes within a few feet of other conductors or earth
3.) The feedline outside radiates or has significant power loss into
the surroundings, so it does not repeat the impedances every 1/2
wl or invert them every 1/4 wl even if we allow for the slower wave
on the outside caused by the surroundings.
So naturally the result is very much unpredictable.
73, Tom W8JI
W8JI at contesting.com
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