Rudy Bakalov wrote:
> If the cage does the radiation, does that mean that the cage has to be the
> entire length of the tower? That would be a no-go for me as there will be 2
> additional rotating yagis on the tower, at 68' and 31'.
>
No the cage can be shorter and actually end at the 30 foot level...but
you will have to check the base impedance to design the proper match.
> I have LOTS of space. How far from the tower should one end of the T be to
> avoid the interaction?
>
At least more than a half wave to reduce interaction especially if the
tower is at or near resonance the way it is...or less if you can
decouple it at RF.
> Also, if I remember correctly from my physics classes, perpendicular wires
> (top of the T and the tower) do not interact; what kind of interaction did
> you experience that I should be aware of?
>
>
> The horizontal wires of the "T" are not doing much of the radiation
> due to the cancelation effect. That is why a T is a great antenna as
> the horizontal radiation is minimized. The imblance that is sure to
> occur is by the close spaced support metal tower in terms of a
> wavelength or less.You could conceivably detune the tower at 1.8 but
> this gets complicated. There are lots of papers, i.e. NAB and IEEE on
> detuning large metal structures such as power line supports to
> minimize the interaction. But IMHO the best thing for you is to go
> with your tower as you should be able to deal with the match presented
> even with a shorter cage below the bottom beam.
Herb, KV4FZ
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