[TowerTalk] 15 meter beam on 40 meter tower ?

[Pete Smith N4ZR]

I'm coming a little late to this conversation, but maybe my experience 
will be illustrative - I had a tribander at 97 feet, with a 2-element 
40-meter short yagi about 10 feet above it.  Until I turned the 40-meter 
yagi perpendicular to the tribander, it completely destroyed the 
tribander's pattern and swr on 15.  Once I did that, all these 
deleterious effects went away.

73, Pete N4ZR
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On 9/1/2022 2:45 PM, Jim Brown wrote:
> On 9/1/2022 11:09 AM, Kim Elmore wrote:
>> I have a KLM KT-34A about 8 ft from and perpendicular to 40CD2. They 
>> each appear unaffected by the other, at least as far as VSWR values go.
>
> I wouldn't expect to see interaction from the elements if they were 
> perpendicular, but MAYBE from the boom.
>
> An easy way to check for interaction between antennas is to model the 
> victim as a dipole with the addition of the potentially interfering 
> antenna as a dipole at the planned spacing, and look for current 
> induced in the potentially interfering antenna when the victim antenna 
> is driven at its operating frequency. If there is significant current, 
> I'd start looking at it's vertical pattern, also varying the lengths 
> of the interfering antenna to simulate the effect of reflector and 
> directors of the interfering Yagi.
>
> If interference disturbs the vertical pattern enough to matter, you 
> can play with spacing until the effect is minimal.
>
> 73, Jim K9YC
>
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