[TowerTalk] 80m Vertical ssb/cw switching

[Tom Rauch]

> While I have not done it, I believe it may be possible to design a
> network of stubs and transformers which 'switches' automatically as
> one moves from the low to the high end of the band. I do not think the
> stub tuning will always be applicable to tuned antenna arrays, but it
> should be universally applicable to single element verticals and to
> dipoles. (I could be wrong).

The ARRL Antenna Handbook describes stub systems that work, 
but they correctly point out that all stub systems add loss and it 
takes a complicated system to significantly extend bandwidth 
without using a switched reactance.

Why so much work anyway? First of all, a Marconi is already 
around twice the bandwidth of a dipole the same thickness 
because the resonant part of the antenna is half the length and the 
system has "infinite bandwidth" in the half made up by a large 
conventional groundplane.

Secondly, just make the antenna thick....especially at the open 
ends where the electric field boundary region is. Anything you do to 
reduce the voltage gradient or field density at the open ends will 
increase bandwidth.

What I have always done is just made bowtie elements. A wire 
cage or skeleton using a few small diameter wires is electrically 
just as good as a solid conductor, and very easy to build.


    

 
73, Tom W8JI
W8JI@contesting.com 

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