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

[Dan Maguire via TowerTalk]

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

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