2 element 20 meter beam on a 5 element 11 meter boom.

[AE5RD]

I have a 5 element 11 meter antenna on a 26 ft boom. I built a 20 meter aluminum dipole. I was wondering if i could build a reflector for the dipole and mount both elements on my 11 meter boom?

 

[W5LZ]

'I.I.I.' Jack,
Sure, why not. With a boom that long, not really any reason you couldn't make it a 3 element 20 meter beam.
- 'Doc

 

[Captain Kilowatt]

Sure,go for it. There may be a slight detuning of each antenna as they may interact with each other.Why not try mounting one set of elements on top of the boom and the other on the bottom.May not make any differance but what the heck. Just make sure the boom will handle the extra load. Those full size 20m elements have a LOT of torque in a wind.I am thinking of mounting a homebrew three element for maybe 12m but most likely 17m on the boom of my 6 element 6m beam.It is homebrew as well and has the boom from an old Wilson Shooting Star.

 

[W5LZ]

Oh they certainly will interact with one another! But, that's taken care of when you tune them both. Tri-band beams have been common for years. Leaving off one of those bands isn't going to be something terrible.
About the only time you run into problems that are sort of hard to 'solve' is when the two antennas are harmonics of each other. Not impossible, just different. And as 'QRN' said, the mechanical aspects need to be considered too. Easiest 'cure' for a 'bendy' boom is a truss.
- 'Doc

 

[KD7UGY]

What if you had a 6 element yagi for 11 meters that was vertical then you put 3 elements for 20 meter's on the same boom but horizontal and they were both fed via a hairpin match, would they interact with eachother?

 

[W5LZ]

KD7UGY,
Sure, but probably not to the point where each couldn't be made to work.
Anything close to any antenna will affect that antenna's tuning to some degree. If that 'degree' isn't too much, then there's not much of a difference, so who cares. If you have vertical and horizontal elements on one boom, then remove either the vertical or horizontal elements, you'll need to re-tune what's left, right?
- 'Doc