[Antennas] stacking beams?

[Billy Cox]

>I would like to stack  two 5 el 6M beams,,, I want to point one East, 
>one West,  I only have about 5 feet between them,  they will use 
>separate feedlines.  Is 5 ft enough separation that they won't "see" 
>each  other, won't interfere with each other?  It worked OK for a 2 
>and 6M beam,  but not sure if 2 --6M beams will work this way.
>Bob W0DXZ

Most likely ... NOT.

Let's look at why that's a possible answer. 

0.5w for 50 mHz is roughly 9.36'  <Using the 468 / 50 formula>

So 5' is roughly 0.25w .... WAYYYYY toooo close.

Recall that stack spacing for additional gain runs in the range
of 0.5w to 1.0w typically ... and you are at 1/2 of that at 5'.

So interactions, SWR problems, and no F/B are some of the
more likely results ... certainly not the stated gain in either
direction, as they will couple to each other, even with the
separate feedlines.

Now, why did the same spacing work when you had a 2m
and a 6m yagi together?  5' at 144 mHz is more like 0.8w
of spacing ... so while there's likely to still be some amount
of interaction ... due to the 0.8w spacing, it will be much less.

By comparison ... 5' of spacing at 144 is roughly 15' at 50 mHz.

So will they work at 5' spacing? Yes, the question is how well?

I'd suggest going for more like 20' if you really need the
gain and pattern to remain close to that of a single yagi.

Hope this helps ...

73 Billy AA4NU