[TowerTalk] 40 meter interaction

[Jay Terleski]

Tom,

Vertical and dipoles have about 30db of isolation between them due to
the polarization being at right angles. So this is good.  If you have
raised radials it may be worse.

I would build it and then measure the interaction by putting a
terminated watt meter at the end of the dipoles feedline to see what
kind of power is coming back down the line. I bet its very small. 

You could model it too, and compare the results with your measurements.  

I would also take great strides to make sure the feedline to the dipole
was not coupling to the verticles. This is probably more of a worry for
you for messing up the verticals patterns.

If you see coupling all is not lost, now you can try detuning the dipole
to take it out of the picture when you not using it.  A capacitor or
inductor across the feedline of the "correct" value could do this.  What
is the correct value? It depends on the feedline length to the dipole,
just an open will do it if its exactly .5 WL. or multiple of .5 WL.

Bottom line build it and make the tests, then let us know what you see.

Jay, WX0B



Tom Osborne wrote:
> 
> Hi TT'ians.
> 
> I now have 3 phased verticals on 40.  They work good for dx'ing
> but suck for domestic contesting.  I'd like to put up a dipole
> here but the problem is it would go right over the top of the
> verticals.  The dipole would be at about the 70 foot point up the
> trees putting it about 30 feet or so above the verticals.  Would
> that screw up the pattern on the verticals by having a dipole
> right above them?  Probably wouldn't help things.  73 and HNY
> Tom W7WHY
> 
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-- 
Jay Terleski
WX0B - Array Solutions
www.arraysolutions.com

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