[TowerTalk] 40M rotary dipole

[jimlux]

On 9/20/17 10:35 PM, Stan Stockton wrote:
> I am curious.  The coax/tower (we'll call it Antenna 1) is isolated from Antenna 2 (the real antenna) with a choke.
> 
> Antenna 1 is still radiating the noise without, let's say, direct connection to Antenna 2.
> 
> So there is no propagation such that Antenna 2 picks up the noise radiated from Antenna 1, end of which is at most a few inches away?
> 

the dipole is symmetric with respect to the noise source.  so a point 
noise source on the tower couples equally to the two legs of dipole, and 
therefore cancels out.

Interestingly, it's the "middle" of the dipole that's closest to your 
source, and that's usually the "most symmetric" part of the antenna. 
Asymmetries tend to be at the ends of the dipole (different height, 
surrounding, etc.)