Topband: DECOUPLING RF

Tom Rauch w8ji at contesting.com
Wed Aug 9 17:16:41 EDT 2006


>I have a 1/4 wave vert with 8 raised radials the feed point 
>is 8 ft off the
> ground it is fed with 600 ohm open wire line would there 
> be any advantage by
> installing ferrite cores to  the radial side of the feed 
> line where the  feed
> line meets the 16 radials i have tried this and what i 
> have observed is the
> swr does not change but am able to couple more power to 
> the antenna given  the
> same amount of drive to the  amplifier as with out the 
> cores  installed...any
> thoughts about this

In every measurement I've made, and these are FS 
measurements where ONLY the antenna being tested is changed 
and nothing else, not choking the feedline cost somewhere 
around 1dB in field strength. That is with a coaxial feed.

I don't know why you would want to feed an unbalanced 
antenna with balanced line without a balun Ray. I certainly 
would not put beads over the ground lead alone. I'd put a 
good choke or current balun at the feedpoint so the balanced 
line stayed balanced.

73 Tom





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