[TowerTalk] Looking for a Short Rotatable Dipole or...

[Jim Brown]

On Fri,4/29/2016 3:30 AM, jimlux wrote:
> I would think that two dipoles, with some sort of adjustable phase 
> combining network might be the optimum strategy. A dipole isn't going 
> to have good directivity for the main lobe, but can have a pretty good 
> null to place on an interferer. 

Jim,

Eric, W3DQ, the guy asking the question, lives in DC on a fairly small 
lot, so his options are pretty limited. I've visited his QTH and my XYL 
and I have enjoyed their overnight hospitality. He's lucky to find space 
and skylooks for one radiator, let alone two. :)  So my reply is in that 
context.

Eric -- another thing to consider is that a resonant 40M dipole in close 
proximity to a 15M antenna can cause significant distortion of the 15M 
antenna's pattern. I don't know if that's also true of a loaded 40M 
dipole. I do know that the C3SS is sensitive to the Z of the 
transmission line feeding it. Glen and I tried a 100 ohm choke on it 
(bifilar #12 THHN on a single #31 toroid) and found that the antenna 
didn't like it. It was fine with the same choke wound with #12 enameled 
copper.

73, Jim K9YC