[TowerTalk] Coupled-Resonator Dipoles (was G5RV vs 40M dipole)

[Roger (K8RI) on TT]

On 4/27/2015 12:12 AM, Dan Maguire via TowerTalk wrote:
> Jim Brown wrote:
>>>> After studying the chapters in N6BT's book that described this technique, I spent time trying to model it, with only limited success. As I recall, I could get good coupling (both match and radiation efficiency) with two bands (one directly driven, one parasitically coupled), I didn't get a third band working. It seems intuitively obvious that while the technique is elegant and the performance of Tom's antennas prove that it works, the design is NOT trivial.
> A detailed analysis of coupled-resonator dipoles may be found as the second bullet on this page:
>
> http://ac6la.com/aecollection4.html

I would think, meaning I don't know, but it seems logical that a fan 
dipole constructed using a multi conductor cable or even close spaced 
wires would have considerable capacitive coupling between elements.  
With the conductors in one cable would the capacitance do more coupling  
than the disconnected conductor acting as a parasitic element?
The more they are separated the more the  unconnected conductor would 
become parasitically driven?

I  hope I got that right.

73

Roger  (K8RI)


> Compared to a fan dipole (elements physically connected at a common feedpoint) the advantages of a coupled-resonator dipole are 1) independent fine-tuning of each element, little interaction between elements, and 2) with optimal spacing it is possible to get an *exact* match to 50 ohms on the higher (parasitic) frequencies.  (The match on the primary frequency will depend mostly on height above ground.)
>
> The disadvantages are 1) narrower bandwidth than stand-alone dipoles and 2) the mechanical complexity.  You need to come up with a way to maintain a uniform and relatively small separation between the elements.  That's easy to do with tubing, not so easy with wires.
>
> Dan, AC6LA
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-- 

73

Roger (K8RI)


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