"Jeff Liebermann" wrote in message
...



What the military used discones for is receive frequency hopping all
over their HF bands without any band switching or tuning. LDPA (log
periodic) broadband HF antennas were also used, which incidentally was
also present at N6IJ:
www.n6ij.org/antennas.html
Neither antenna had much gain, but they sure had the bandwidth.

--
Jeff
++++++++++++++++++++++++++++++++++++++++++++++++++ ++++++++

They were also used for HF transmit on some ships.

Here's a link to an early Navy research paper on the discone/cage
antenna sometimes called a "discage." Unfortunately, only the text
is clear; the pictures are not good.

http://www.navy-radio.com/ant/discage-661464.pdf

Note that a single structure was fed from the top and the bottom by
two separate coax cables.

I had hundreds of inspection and test visits to Navy ships in the 1980s
and 1990s. In practice, I never saw that antenna installed for use
at the extreme low end, as described in the linked paper. There was nearly
always a fan antenna for 2 -6 MHz.

The discone/cage freq ranges were nominally 4 - 12 MHz (cage) and
10- 30 MHz (discone). Both sections were invariably fed through a
multi-transmitter coupler, either four or eight transmitters, depending
on the ship.

I know the fan antennas all had custom matching boxes at the
feed point to bring the SWR within the 3:1 circle. I can't recall if the
sections of the discage also had such matching.

"Sal"
(really KD6VKW)