[TowerTalk] Liberal Arts Question on Dipole Antennas

[Scott Townley]

Terry Conboy formerly of USWest Cellular?

At 16:26 2006-06-01, Terry Conboy wrote:
>At 07:26 AM 2006-06-01, Lee K0WA wrote:
> >   Is there an interaction between the tower...the 80 meter
> > antenna...the Vee to the east?
>
>I put your 40m inverted vee and the adjacent 80m inverted vee into
>EZNEC (as I understand your layout), and as others have suggested,
>the 80m antenna does BAD things to the impedance of the 40m
>antenna.  How bad will depend on the tuning of the 80m antenna, the
>length of its coax, and what you have connected to the TX end of the
>80m feedline when you are using the 40m antenna.
>
>Unless you need to operate 2 bands at once (which is scary, given the
>small spacing of the two antennas), you would probably be much better
>off putting both the 40 and 80m antennas in parallel on the same
>feedpoint.  I've done this for years with quite good
>results.  Depending on the spacing of the 40m and 80m wires, you may
>have to lengthen the 40m legs a bit to get resonance back in band.
>
>You may also want to consider a balun at the feedpoint, since you can
>get a fair amount of current flowing on the coax shield and/or the
>tower, depending on their dimensions and where they find a path to ground.
>
>Good luck,
>Terry N6RY
>
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