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.
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|