[Elecraft] RF in the Trees

[Vic, K2VCO]

I have a theory about this.

Compare a vertical to a dipole. One reason for additional noise is that 
a vertical is omnidirectional, and noise comes from all directions. The 
signal is coming from one direction, and if it is the right direction, 
then the 2.2 dB gain from directivity of a dipole improves the s/n ratio 
by that much. But subjectively the difference seems greater than this. 
It's also true that the vertical is better for signals off the side of 
the dipole.

As Brian said, most verticals appear to be far noisier in urban 
environments where there is a lot of manmade noise. I believe that this 
is /not/ because manmade noise tends to be vertically polarized, as is 
often said.

I believe that it is because most verticals are not adequately decoupled 
from the feedline. Therefore, manmade noise is picked up on the outside 
of the feedline and flows directly into the antenna.

This is exactly the same problem that happens with a dipole without a balun.

Therefore the solution to the problem may be a good choke 'balun' at the 
vertical's feedpoint.

On 6/26/14 1:38 PM, Brian Hunt wrote:
> The other thing I have encountered with verticals vs horizontal antennas
> in an urban environment is that verticals are inherently noisier.

-- 
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/