[TowerTalk] Looking for a Short Rotatable Dipole or...

[Patrick Greenlee]

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 at 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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