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

[Patrick Greenlee]

George, I can't say one way or the other, could be the antenna in 
question or something similar.  I never personally touched one but saw 
plenty of them atop tuna boat masts and crow's nests as well as some at 
residences.  It seems to me to be an easy way to get on the air with 
something with some directivity and "aimability", at least with useful 
steerable nulls. I like solutions sans traps when available.

Patrick         NJ5G


On 4/28/2016 7:52 AM, George Dubovsky wrote:
> Patrick,
>
> Back in the day, a company called Kirk made a series of what they called
> "helicoidal" beams. The elements were tapered fiberglass with approx 1/4"
> wide, thin copper strap wrapped around in a spiral, and the whole thing was
> covered with something like spar varnish. Ring any bells?
>
> 73,
>
> geo - n4ua
>
> On Thu, Apr 28, 2016 at 8:44 AM, Patrick Greenlee <patrick_g at windstream.net>
> wrote:
>
>> 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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