[CQ-Contest] Feedline length

[Tom Rauch]

> > 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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