Although Weight is the primary reason "I think" for using plastic or
wood spreaders, you can purchase 1/4", 5/16", and 3/8" thin wall, soft,
aluminum tubing at the local hardware stores. It's not cheap and would
require care in fastening the cage wires to prevent intermittent contact
which I'd think would result in noise. OTOH that noise might be less of
a problem than a rusty fence nearby.
The 1/4" could easily be bent into a 1' diameter circle and maybe 5/16"
could as well. Swaging tools could be used to expand one end so the
other could be inserted and sealed to form a stable ring. That's
roughly 3.2' of tube per spreader. That being the case you would
probably spend about $30 USD for the spreaders on a 75 meter cage
dipole, 1 foot across. Add to that the required wire, holes drilled in
the rings to take the wire, AND the time required for gathering parts
and fabrication I think it might turn out to be quite a project. OTOH a
Fan dipole only requires one spreader, but one much more substantial.
With the fan dipole the ends can just be tied off using cord, or they
can be tied together with a wire across the ends or a conductive
spreader to form a giant Bow tie.
So the question now: Is the Cage Dipole better than the Fan or Bow Tie
dipoles, particularly when all the extra effort to build a Fan Dipole is
taken into consideration? Then is there any difference between a side
by side configuration compared to an over and under configuration?
I'm beginning to consider building several 75 meter "Bow Tie" antennas
as I'd like to minimize the tuning required as I have a solid state amp
that is very unforgiving of very little SWR.
73
Roger (K8RI)
Roger (K8RI) wrote:
> The cage dipole simulates a conductor of much larger diameter than any
> of the single wires, or even their total and the ends are tied together.
> That being the case, other than simplicity and weight, why use an
> insulator for the separator? How about a thin metal band, Aluminum
> ring, or what ever? Wood has been used, wood soaked in paraffin as
> well as other materials, but I've not seen any metal used. A disk would
> be out except for small diameters due to the aerodynamic problems.
>
> As a personal opinion I'd stick with 6" and larger diameter cages on 75
> and 40 for the increased band width. Actually I thin 1' would work well
> on 75.
>
>
> 73
>
> Roger (K8RI)
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