I have a problem, the flow is poor between the AP1 and AP3, Bandwidth Test between AP 1 and AP2 is ok, 20MB, AP2 and AP3 between the same 20MB ok, but between AP1 and AP3 is 5MB, it is a problem, we have 5 MB! I think the problem is to bridge the AP2, something happening here, I tried everything, I do not know what to do, you WDS?

Any suggestion is welcome!

you most probably got two WLAN-Interfaces interfering with each other.

Are both WLAN-Interfaces on one Routerboard?
If yes: try two separate routerboards with one WLAN-Interface on each.
If not, try frequency more separation. And find better ways to shield the RF components againt each other.

The AP 2 including federal 5ghz two cards, one beside the other, and the antennas are next to each other (29dB Grid and 23dBi Flat Panel). When I do a test flow from AP1 to AP2, CCQ drastic decline between AP2 and AP3!

this sounds like interference when using multiple WLAN-interfaces on one single routerboard.

o, divide AP2 into two routerboards.
These routerboards must be interconnected and must sit in their own metallic/shielded housing in order to avoid interference.
This will most probably solve this issue.

My problem is the antenna spacing. The distance between the grid and the panel antenna is 20cm. What should be the difference between them without being a nuisance?

Clearly, a lot more than 20cm! Even if you use two separate routerboards, you will still have RF interference on your mast anyway. Make the two RF channels as far apart as possible. Make the two antenna as far apart as possible vertically. Moving them horizontally will not have anything like the effect as vertically mounting them apart.

The exact distance apart depends on too many variables. Just go as far as you can, but obviously while the link still works. No point having one on the ground and the other at the top of the mast!

Will it help me to relocate panel antenna 3m horizontally to the second pillar?

They need to be moved vertically apart for best effect. But if you want to give it a try, what have you got to lose? At a very rough rule, you get about 20-30db better isolation vertically than horizontally for the same distance. You could also try turning one link over to be Horizontally polarised and the other link Vertically.

Do not mount both coax cables of both systems near to each other either. I have seen engineers make their tower very pretty by tywraping all their coax cables together in one neat bundle and then get interference. One of those occasions when it's good RF engineering practise to be a little untidy and NOT to lock all the coax cables neatly together.

Thanks for your help I'll let results!

Problem solved, I moved 3m panel and put the next pipe, and now everything right! Thank you all for your help!

Don't forget to also give sup5 some karma, he was first with the suggestion it was interference.

Glad we helped