stacked Yagi question

[anneranch]

In general
1. If optimal Yagi height above real ground is 1/2 wavelength
should 14 MHz ( single bander ) Yagi be on bottom of the stack and
7 MHz (single bander ) Yagi be on top of the stack
1/2 wavelength distant from the bottom 14 MHz yagi ?

This is a theoretical , electrical question ,
disregard the mechanical challenge of installing these
"stacked Yagis ".

2. To minimize interaction between the antennas - should they be
mechanically "pointed" 90 degrees from each other ?
They are used by TWO independent transmitters simultaneously .


I am asking for educated opinions , I am and will eventually model the setup.

 

[sonm10]

No one has replied yet, and, for the record, I don't do HF, however,

It would seem as if a Fan Dipole would be more simple. Multiple dipoles fed with a single feed point. My apologizes, I do not know the necessary height to make a fan dipole work.




Images from Microsoft Bing

 

[sonm10]

What are you trying to achieve with the yagis? More gain in a specific direction?

 

[paulears]

I've viewed the ½ wave distance as one to NOT go below, but above is fine. After all, VHF and UHF antennas work best the highest you can get them. In terms of pointing them different ways, my understanding is that the destructive factor is the impact of a lump of metal becoming an unintentional reflector under your antenna - and the orientation of a typical 'H' shape of metal is not very different 90 degrees rotated. For size reasons, my lowest height antenna would be the lowest frequency one, but if the physical layout made a lower frequency one be further away from the others, I'd probably do that.