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

[jimlux]

On 4/28/16 6:09 AM, Patrick Greenlee wrote:
> 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?
>>


This idea of a spiraled element has been around for decades.  From an 
electrical standpoint, it's not a whole lot different than a loading 
coil at the base:  the radiator being "physically short compared to a 
half wavelength" means that it's going to have a lot of capacitive 
reactance which you have to tune out in some way.