I want to establish 5 Ghz link using 2 CM9 cards, 2 pc routers,2 flat antennas, distance 2.5-3 km and mikrotik.Any experiance, comments?

If you use grid antennas at least 22dBi and if there are no obstables, there should be no problem. In the situation I had, there was one AP with omni antenna 12dBi 5.8Ghz and 2km away bridge station with grid antenna 22dBi 5.8GHZ also and I had weak signal, although it worked with no ping loss. I switched to Ubiquity SR5 at both places and I got much better signal. If changing cards is not an option in your case, you should go with higher gain antennas, maybe 26 or 29dBi. Otherwise Wistron Neweb CM9 works good with Mikrotik (2.8.26 in my case).

There is no need for stronger antennas than 22db for that distance at all... it will work full 54 mbps even G-turbo will work fine at that distance...

acid

I have the same problem as you with same specifications.
Do you have bought antennas from hyperlink?
Pigtail too (U-fl to N-type)?
I think now the pigtail is the problem.
I have a loss of 21dbm between calculations and reality and this at 4.5m.
I have changed the 22dbi with a 3db duck (so I have no cable) and the loss
is the same so the only what it can be is the pigtail ...
I've also used several OS to test.

I have a very very poor signal at 3.5km (-84dbm) with SR5. CM9 no chance to see a signal

But not the biggest "joke"
I have tests CM9 now in 2.4 GHz and the signal is exactly like calulated with an
sma omi of 5dbi and SMA pigtail and connectect this to the other antenna connector.
The joke now is that in 5.8Ghz the signal is -38dbm USING the 2.4 antennas
and -59dbm with the 5.8 antennas and yes I use the right port ...
I have removed the 5.8Ghz antenna to verify that and it is so.
The only thing I don't know yet is if the antenna is for 2.4 and 5.8 ghz.

So the uf-n-female connector is realy the bad one.
And the singnal is exactly the calulcated (loss of pigtail 3dbm, cadr 17dbm, distance 4m)

So people what do you think of this joke??

I want to establish 5 Ghz link using 2 CM9 cards, 2 pc routers,2 flat antennas, distance 2.5-3 km and mikrotik.Any experiance, comments?

3km you shouldn't need more than a 15dB pannel... That's a very short distance.. As long as you have a clear frenel zone and LoS your good. To give yourself extra fade margin you could increase the antenna gain or use a higher powered card, (ex: SR5) however you should be able to achieve stable signal levels with the formentioned specs.

Hi, a 5.8ghz link has been working away very well for a few years here as part of Irishwan ( http://www.irish-wan.com ),with Mikrotik on each end ,atheros 5211 cards,and small panel antennas from Superpass,over about the same distance.The only trouble was one panel split open (glue failed ) and last week a powercut killed one box and corrupted the flash module.I emailed support and got a response straight away.....