[TowerTalk] 160M vertical dipole ?

[Lux, Jim]

On 1/23/22 9:46 AM, Robert Harmon wrote:
> No I don't have a 260 foot tower :-)    but thinking about this crazy idea.
>
> My HDX590 tower is 90 feet fully extended.  By attaching to the side of the mast 15 feet up I can have an attachment point at 105 feet.
> I am envisioning hanging a vertical dipole from the 105 feet point and running the top wire horizontally 82 feet sloping down to a 30 foot mast at the corner
> of my property.  Likewise on the lower end of the dipole 9 feet high and going to the other corner of my property.  This woud put the center of the dipole about 57 feet
> above the ground.  I don't know how a dipole will work with the ends bent this way but maybe it would be more efficient than a vertical with a compromise radial field.
> An option might be to make two big boy loading coils and shorten the dipole.
> What do you think of this idea ?  Am I off my rocker ?  hihi


You're not off your rocker, but pay attention to the inherent problems 
with vpol being strongly affected by the soil properties in the area - 
particularly for low angles.

What's interesting is that the directivity of a infinitely short dipole 
is 1.5 dBi, and a full size half wave is 2.15 dBi.  So a shortened 
dipole with capacity hats, loading coils, or matching network will be 
pretty much the same (within a 1/2 dB) as far as the far field goes for 
the same center height.

Your issues are going to be losses due to the fields interacting with 
the soil AND losses in your matching networks (whether at the feed or 
loading coils, or whatever). The radiation resistance is smaller, so the 
current in the antenna (for the same power) will be higher, so you get 
more IR losses.

Those can be driven down by using bigger wires, etc.

The other thing that happens is that the impedance will vary more 
quickly, so you might need an adjustable matching network.

You might also look at making the bottom of the dipole a "cone" (even 
shortened), because that improves the matching bandwidth. Cones (and fan 
dipoles) are broader band than single wires.