Re: [Amps] antennas that are 1:1 vswr all over the band

[David Kirkby <david.kirkby@onetel.net>]

donii@sympatico.ca wrote:

> Gentlemen
> A while back as I was listening to two rag chews on 80 they mentioned 
> some kind of antenna that was extremely expensive and that could 
> adjust its length according to the frequency transmitted. This must 
> have been for 20 and higher. I don't know anymore as I wasn't really 
> paying attention. Anybody know of this type of antenna? Could it be done?
> Peter
> VE2FAR

Not what you want I am sure, but here's an interesting exercise for 
those with some AC theory. The relevance to your  question will be 
apparent to anyone able to get the right answer.

Calculate the resonate frequency of this circuit, which I will try to 
draw, but will describe too, in case my graphics are too bad to understand:

   |
   |
|---|
|       |
L     C
|       |
|       |
R     R
|       |
|       |
----
  |
  |

You have a L in series with an R. You have a C in series with an R. You 
then put the series RC and series LC in parallel with each other.

Now make R=sqrt(L/C) and find the resonate frequency.

f=????

G8WRB.



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