This post should have shown up yesterday, but instead of converting to
plain text it bounced which I didn't receive until this evening.
David Gilbert wrote:
> How so?
>
> Even a 0.5 inch cross section the length of a shortened 40m or 80m
> antenna adds up to more area than the cross sectional area of a coil,
> with a greater percentage of it up high where the leverage is greater.
>
> And as someone else here said, it is easier to build a strong vertical
> out of aluminum tubing than any kind of insulator that would be required
> for a helically wound antenna.
>
Working a lot with both materials I seriously doubt the above statement.
Fiberglass with the strands laid out linear with the occasional
helically would strands would be stronger than aluminum and fairly
rigid. You can vary the rigidity by varying the ratio of linear to wound
strands. You can also construct a tube formed on a mandrel that will be
strong and light. Once the design is set the wire is just wound on the
form and coated with resin, or a fiberglass and resin mix. They now
make airplane wings out of the stuff instead of Aluminum including the
new Airbus and its competition. Carbon fiber is stiffer and stronger,
but makes very poor antenna supports due to its conductivity.
I'd take the fiberglass over Aluminum any day. OTOH that may be because
I work with it so much.
The main drawback for the fiberglass is the resin's susceptibility to UV.
However there are tradeoffs. The center loaded antenna is more
efficient compared to the linear/helically wound antenna and one with
top loading is even more efficient (or can be depending on the height of
the antenna and the size of the top hat).
BUT a good center loaded mobile antenna has a "large" coil on 75 and 40
compared to the size of a helically wound antenna. The capacitively
loaded antenna presents even more drag.
73
Roger (K8RI)
> Dave AB7E
>
>
>
>
>
> Roger (K8RI) wrote:
>
>>
>> But a center loaded vertical has a high profile, high wind drag, and is
>> more fragile than the helically wound vertical.
>>
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