Yagi spacing

[W9BHI]

Hello,
This one is for all of you antenna gurus.
I am planning to put up a 3 element 10 meter yagi and a 4 element 6 meter yagi on the same mast.
What would be the proper vertical spacing between the two?
They will both be horizontally polarized.

Thanks,
Don W9BHI

[KA2DZT]

Don,

Put the 6M beam above the 10M beam.  I would think you should space at least a 1/2 wavelength of 6M.  More if you can.

Fred

[W9BHI]

Thanks Fred,
Thats kind of what I thought.

Don W9BHI

[W4AAB]

Sounds right. I used to space my 6 and 2 meter Yagis 4 feet apart, and had no interaction ( the booms on both antennas were in the 24 foot range).
                                                         Joew W4AAB

[KM1H]

This subject can often start bar fights but pratically speaking 3-4' is sufficient and the 6 below the 10 if you want to get into little details that mean little in use.
Models will tell you too much at times resulting in brain overload resulting in indecision

If the 6 appears to be noticably affected then push it up a foot at a time until youre happy but its really very hard to destroy a yagis gain.

I ran 4 el 20-10 monobanders in the classic Christmas tree at 6' spacing and those booms were 40, 27, 20' and no interaction noted.

Carl

[KA2DZT]

In the many years of installing TV antennas, I would see installations where two TV antennas were on the same mast.  I'd see this mostly in old apartment complexes.  The antenna that was under would receive poor reception while the antenna on top worked fine.  Same was true if two antennas mounted on separate masts but were aimed where as one antenna pointed into the rear end of the other.  These antennas would be rather close to each other, maybe only 10-20ft apart.  The antenna that was behind the other worked poorly.  This was not true if the antenna was higher than the one in front.

My opinion, I would mount the 6M beam above the 10M beam.

Fred

[Pete, WA2CWA]

I always put the heaviest beam lowest on the mast. Currently, my 5 element tri-bander sits directly above the top of the tower, 5 feet above that is 6 meter beam, 5 foot above that is the 2 meter beam.

[KM1H]

I always put the heaviest beam lowest on the mast.

That of course is the best mechanical configuration but pattern modeling sometimes disagrees and has been brought up in print and on the Internet many times.

There was no way I was going to put a full size 4el 20M yagi with a 40' boom at the top!

Unlike TV antennas which have multiple resonances so are really a completely different subject, the 6 and 10M yagis do not share that problem.

Those 5-6 band ham yagis can become a problem since 6 and 12M will interact as will log periodics.

Im currently sharing an all HB array of 3el 20M, stacked 28 el 32' booms on 432MHz, and a 35' boom 8 el 6M in that order, bottom to top with about 11' of mast exposed with no apparent interaction....the observed patterns and performance are as modeled.

What did not work was when I tried a TH-6DXX about 7' above a 4el 40M KLM on a 42' boom. The TH6 was dead on all 3 bands when I tried it as a contest multiplier hunter; it was fine when tested by itself earlier. The KLM was unfazed.

Carl

[KA2DZT]

Carl,

You're correct about the TV antennas, they will interfere with each other because they have shared resonances, as you pointed out.  6M and 10M antennas don't have that same problem, but it's seems better to put the smaller antenna on top.  I didn't always do that with separate VHF and UHF antennas.  Sometimes I mounted UHF antennas under VHF antennas.

Fred

[KM1H]

On the 100' tower here I had 4 el 10 and 15 at the top and bottom respectively on about 14' of mast with a long boom pair on 2M in between at 12' spacing and than a pair of 222 in between them, and then a quad of 1296 in between them. It all seemed to work well since what I heard I could work.

Carl