[TowerTalk] Looking for a Short Rotatable Dipole or...

[jimlux]

On 4/28/16 5:49 PM, Roger (K8RI) on TT wrote:
> Just another thought:
>
>  30' pole on the roof supporting 5 center fed, half wave sloping
> dipoles. I have used a couple, but if you have the room, use the 5
> switched dipoles.  I believe it's in either the ARRL handbook, or the
> Antenna handbook..  They are simple, seem to work stateside and DX.
> Switched as in the handbook, the have a little gain and a bit of a F/B
> that really helps.
>
> Even 2 or three will give a bit of directivity.    I'm thinking of
> switching to 75/40 fan dipoles and experiment with the 5 antennas
> instead of just a single monoband on 75 and one on 40 at present. Wire
> is cheap and easy to experiment with.  I've worked all continents with
> just two 40 meter slopers and an AV640 (on 40) at 25 feet.


I would think that two dipoles, with some sort of adjustable phase 
combining network might be the optimum strategy.  A dipole isn't going 
to have good directivity for the main lobe, but can have a pretty good 
null to place on an interferer.

There was a clever scheme in one of the antenna compendiums where there 
was a adjustable LC, a combiner, and a DPDT polarity reversing switch.

You adjust the two knobs on the LC to minimize or maximize the signal as 
desired, flip the switch and what was maximized, is now minimized.