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

[Bob Shohet, KQ2M]

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.

73

Bob KQ2M


From: rlvz--- via TowerTalk 
Sent: Sunday, August 19, 2018 1:40 PM
To: towertalk at contesting.com 
Subject: [TowerTalk] Do some HF Tri-Banders receive more noise than others?

Hi Guys,


I believe some HF Yagi antennas receive more noise than others and I'm wondering if any of you have noticed the same thing?
 
I've got two Tri-Banders located on different towers, in the same yard, at aprx. the same height AGL, and one of them receives 3 S-units more noise, on average, than the other when the antennas are pointed in the same direction regardless of what direction they're aimed, though the received signals are usually identical. 

 
More specifics: both use the same model Force 12 Balun, both are fed with 1/2" heliax, and both go to the same Stackmatch antenna switch.  One antenna is a Hy-Gain Tri-Bander which has grounded elements including the Driven Element which is grounded at the boom through it's Beta Match, and this is the "quiet" antenna.  The other is a Bencher Skyhawk which has it's Driven element isolated from ground.  I'm wondering if the Hy-Gain may be quieter since the Driven Element is grounded at the boom which the Skyhawk isn't?
 
By the way, I ran the test of disconnecting the shield of the PL-259 at the shack end of the Skyhawks coax to see if the antenna got quieter or noisier to determine if the addition of a "Noise Balun" would reduce noise on the Skyhawk.  The noise level increased with the shield disconnected, so I'm told a Noise Balun like Palomar produces wouldn't help reduce noise on the Skyhawk.   

 
I ask this question because the Skyhawk is too noisy for weak signal work and I'm thinking of replacing it with another Tri-Bander that has a grounded Driven Element if it's likely to receive less noise.
 
Thanks in advance for your thoughts.
 
73,
Dick- K9OM