Topband: Broadband vertical

[Tom Rauch]

> I agree with Herb 1000 %  I also switch to cage feed
antennas here on the high Desert because the ground out here
is very poor .

Changing to multiple drops won't do a single thing to change
ground losses. Nothing, nill, zip.

It only affects the generally small I^2 R losses in the
raditor itself and in the gamma system.

My recollection is that has been measured, and has been
documented in NAB papers.

> My verticals are 70 foot top loaded ( t ) with 62 radial
on each of them I have 6 cage wires 8 foot across the cage .
My bandwidth  is 1.8 thru 1.933 SWR less than 1.2 1  The
unipole is easy to install requires little tuning . No high
price vacuum  caps required  .

> My change from a single wire to a three wire cage unipole
certainly made
> my antenna bandwidth useable. I think several NAB tech
papers on this
> suggest that the copper wire cage also increases the
overall efficiency
> of the radiator.

Herb is correct. The efficiency of a radiator will go up
when the circulating currents or VAR power is reduced, all
other things equal. The loss of efficiency caused by poor
ground doe not change, since the net current flowing in the
ground remains the same.

There is a small (probably inconsequential) improvement in
matching loss when moving from a high operating Q system to
a low operating Q system. The real advantage is bandwidth.

73 Tom