[TowerTalk] Do some HF Tri-Banders receive more noise than others?

[Jim Brown]

On 8/19/2018 11:11 AM, Bob Shohet, KQ2M wrote:
> Dick,
>
> Are your antennas at the same height or different heights?  Is the grounding of each tower the same?  Did you use the identical RF chokes on each antenna?
>
> Any differences of these factors could dramatically affects differences in noise level experienced between antennas pointed in the same direction; especially differences in height and RF chokes.
>
> I would also look at proximity of the towers to potential noise sources.  If a potential noise source is 50’ from tower 1 and 150’ from tower 2, that alone could make a 1+ s-unit difference in noise level, depending on the type of noise source and its polarization.
>
> And differences in physical proximity to the noise source could also affect the beam heading to that noise source for each antenna.  So, for example, in the event of a noise source 50’ from tower 1 at beam heading peaking 270 degrees, at 150’ from tower 2, that noise source might have a beam heading dramatically different.  Just another potential factor to consider.
>
> I do also believe that the physical design comes into play – from my own experiences, even some monobanders pick up more noise than others.  I have to believe that that would also hold true for tribanders even if the physics are different.

All of these comments are well taken.  I would like to emphasize the 
importance of an effective common mode choke at the feedpoint that 
prevents pickup on the feedline from filling in nulls in the antenna's 
pattern. In addition, the design of the antennas themselves can strongly 
influence how noisy it is by control of its directional pattern in three 
dimensions. G0KSC, one of today's leading designers of Yagi antennas, 
has emphasized this in the descriptions of his designs. Two excellent 
interviews of G0KSC by N0AX were published a few years ago in National 
Contest Journal.

73, Jim K9YC