[TowerTalk] Linear Resonator

[Roger Parsons]

Jim, K9YC wrote:
Before doing anything serious with the tower, I suggest that you first do an NEC model of your 160M antenna(s) including the tower and study the interaction.  You might find the interaction is beneficial, or not. Over the spring and summer I did that and found strong interaction between the tower and my original Tee vertical, and also between that Tee vertical and some sloping wires I had rigged off the tower to act as TX verticals.  Further work allowed me use that interaction to provide useful gain in three directions. 
73, Jim K9YC

I had already done an NEC analysis of the tower, but the physical situation is quite complex, and I had simplified it to make it practical to model. NEC says the interaction is there but not dramatic - but it thinks the tower is not much more than 5/8 wave in height.  The situation is quite different if the tower is actually an electrical three quarter wave and I really don't know whether it is or not.


The real tower has four sets of guys, and the first insulators are spaced out from the tower, so those stubs would have to be included. There are 5 different VHF and UHF antennas at different heights on the tower, including one that extends above the top, and those and their feeders would also have to be included. There are various brackets and lighting fixtures. I would actually have to measure all those distances which would mean climbing to the top of the tower.

The use of a linear resonator at the bottom of the tower, if it provides enough isolation, makes the tower appear to be ungrounded and it doesn't then much matter if its electrical length is 5/8 or 3/4 wavelengths. It would also be quite easy to do.


I'm sorry if I hadn't explained the above more clearly in my original post. I would still appreciate comments on whether the linear resonator would still work properly allowing that it could only be applied to the tower structure and not to the cables feeding the other antennas.

73 Roger
VE3ZI