Topband: 160m Ant on 80m?

[Tom Rauch]

> I believe your antenna should simply look like a vertical halfwave dipole,
> except electrically off-balanced by the coil at the top end.  In theory,
any
> simple vertical one half wavelength or less and close to the ground should
> have a single lobe at a takeoff angle determined by radials and ground
> characteristics.

It is really hard to predict what will go on with 80 meters without modeling
the antenna or trying it.
It would all depend on what it looks like on 80, and that would depend on
how much L the antenna has and what is above the L.

If it was a 100 ft vertical with all hat it would indeed behave like a
near-1/2 wl on 80.

A modest loading coil of 170uH 90 feet up would make the base impedance 95
ohms +220j on the second harmonic. That isn't acting like a half-wave by any
means!

There are combinations of coil size and capacitance above the coil that
could seriously hurt 80 meters, and some that won't bother it at all. Short
verticals are the worse ones for having noticeable problems. It should be
pretty safe with a tall vertical, but the base impedance might really be
surprising.

73 Tom