[TowerTalk] Tribanders on separate towers

[Jack Brindle]

This is a scenario where the use of a VNA/VNWA can be helpful. Attach one port to one of the tribanders, the second to the other, then you can plot return loss between the two. Yes, even one of the popular hand-held devices can accomplish this. Set each in a direction, then test. Repeat at different directions until you have enough plots to tell you how much interplay you will get, and then know which directions to avoid. This method is incredibly useful when trying to determine how much filtering you need for bands/antennas in an SO2R environment, but is also useful for antennas on the same bands.

This will not tell you how the signals will mix and match. For that be sure to follow Gary’s usually excellent advice!

73,
Jack, W6FB


> On Feb 3, 2026, at 1:36 PM, Gary Johnson via TowerTalk <towertalk at contesting.com> wrote:
> 
> The pattern can get kinda strange when Yagis on separate towers are both driven. Odd lobes and nulls depend on pointing and may not be intuitive. AC6LA has an example generated with AutoEZ. YMMV. Simulation advised.
> https://ac6la.com/aecollection5.html#:~:text=have on hand.-,Coupled Yagis on Separate Towers,-A question was <https://ac6la.com/aecollection5.html#:~:text=have%20on%20hand.-,Coupled%20Yagis%20on%20Separate%20Towers,-A%20question%20was>
> 
> -Gary NA6O
> 
>> 
>> Subject: [TowerTalk] Tribanders on separate towers
>> 
>> Hello Towertalk 
>> 
>> I?ve been considering installing multiple triband Yagis (interlaced element types, say 4/4/8) at my QTH to be able to switch directions quickly or power split in multiple directions. Installation heights can be between 50-120? and the towers are between 100-200? apart. Some time ago ISTR Frank W3LPL saying this arrangement would need careful modelling (maybe it was on a CTU presentation) but I?ve not been able to find this information since.
> 
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