Once upon a time a long time ago in San Diego many members of the tuna
fleet were equipped with 4 band HF antennas called cat's whiskers (due
to appearance.) They were 4 sets of horizontal dipoles driven with a
single coax feed to a common midpoint. The dipoles came close together
at their midpoint(s) but were "splayed" out several degrees so that
farther out from the center point they were farther and farther apart in
3 dimensions, not 2. The elements were copper wire wrapped helical
fashion on stout fiberglass poles. The wire was secured by a top coat
of resin. I'm not sure if it was epoxy or polyester resin but it was UV
resistant and lasted well in the harsh marine environment.
There was, of course, some interaction between bands when trimming to
tune for initial setup. Most installations did not use antenna tuners
but some skippers and some navigators were hams and some of these used
tuners to broadband the antennas for ham as well as marine HF bands.
This sort of antenna is fairly easy to DIY. Being balanced
aerodynamically they put a light torque load on the rotor/rotator due to
wind. They are relatively light weight and don't require a super HD
rotor/rotator.
Some of the users in the tuna fleet did not employ a rotor/rotator and
instead turned the boat to aim the antenna, an option of which many
residences can't avail themselves. There were some cat's whiskers
installed at residences of hams in the family of tuna fishing hams and
seemed to work satisfactorily. I regret not being able to quote
chapter and verse as to source, mfg, etc but this was some decades back
so I'm claiming "Senior Privileged" employing selective memory.
Patrick NJ5G
On 4/28/2016 6:46 AM, kr2q@optimum.net wrote:
I googled your QTH and the QST article antenna probably won't work in your
situation since your
roof tower is way too short and the "dangling wires" will hit your house.
Since you are a real ham (IE, cost is a factor), check this out and maybe you
can get some ideas for
a modified approach for a shorter version.
http://www.pa1m.nl/pa1m/a-shortened-40-meter-rotary-dipole/
GL
de Doug KR2Q
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