Hi,
I have an RB532 with R52 miniPCI onboard configured as AP-BRIGE.
the ap interface is into a bridge with the other 3 ethernet port of the RB532.

When I connect the the antenna omni to the miniPCI the noise floor showed in the status windows on winbox is between -70 dbm and -78 db.
When I disconnect the antenna the noise floor goes to the expected values -99 dbm.
I have tried:
- substituite the miniPCI, results are the same.
- I have sobstituite the antenna and cables, results are the same
- I have changed the antenna with a 2 db omni antenna, results show a -99 of noise floor, but power is very low, so clients cannot connect.
- I have changed antenna mode from antenna A to antenna B, and connected the antenna to connector B also and the issue is showed to antenna B.

I have others 4 Access point with RB112 and RB532 configured like this one described above and the noise floor is around -98 dbm.

What could be the issue?

On the manual I have not found nothing about this parameter.
From my knowedge the SNR is calculate signal form the client - noise floor of the board.
If noise floor of the board is -90 and a client connected to the AP send a signal that after attenuation arrive to -70, the SNR (or signal strength) is 20dbm. but is noise floor is -70 the SNR is 0 db, = no communication.

BR
Max

Have you changed channels to see if the noise is another active AP on the same channel you are using?

Yes, at the end the channel 3 and 7 are the only with -99 of noise floor .
I will check with the spectrum ana.

The MT does not view frequency activity

Also I have to add some info.
the SR52 must be set to b-only to work fine at channel 3 and 7.
in this AP I have 3 clients connected, when they will be connected.