[TowerTalk] Coaxial Moxon

[Steve Hunt]

Dan,

You got there before me!

This design cannot work satisfactorily as shown. Not only are the 
"integral stubs" very lossy, as you point out, but the Reflector is 
totally "closed" (inner and outer shorted at both ends) so there cannot 
be any velocity-factor shortening effect - it certainly wont be resonant 
anywhere near the intended frequency. My guess is it's close to 
operating like a very lossy dipole.

Thanks for pointing to my web-site  - it was this particular web page 
that prompted me to do the experiments and the write-up!

73,
Steve G3TXQ

Dan Zimmerman N3OX wrote:
>> A quarter wave coax, shorted at the end shows an infinite impedance.Is it
>> possible what is described in the link?
>>     
>
>
> A coax just a little bit shorter than a quarter wave shows a VERY quickly
> changing inductive reactance ... so you can change the stub length +/- a few
> centimeters and find the exact value of reactance you need to load the
> antenna.
>
> But, it's VERY lossy to operate a stub near resonance as a reactance.  I
> estimated something like Q = 1 or Q= 5 for the "quarter wave" (actually a
> little shorter) stubs in that antenna, and a model of it seemed to suggest
> that the gain would be *negative 10dBi* and it would have zero F/B ratio.
>
> You might look at http://www.karinya.net/g3txq/coax_antennas/ as well.
>
> 73,
> Dan
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