Adaptive Gain allows the RF Pre-Amplifier to reduce their gain in the presence of strong adjacent channel or in-band signals causing intermodulation or blocking interference. Not for weak signals causing interference.
See my posting on this subject previously: http://forum.mikrotik.com/viewtopic.php ... 27&start=0
If you are getting interference from unwanted sources, reduce the aperture (beamwidth) of the antenna as this reduces what it can see so that (hopefully!) it also stops seeing the signal that is causing you the interference. It also increases the receive gain of the system, thus improving the S/N ratio. This usually translates into antennae with a higher gain.
Also, a well designed antennae (rather than one copied to look the same as another but actually using different materials and very slightly different dimensions) should have less sidelobes, therefore less opportunity to pick up signals outside of it's main beam. Poorly designed (cheap?) antennae tend to have sidelobes that look in all the wrong places, thus increasing interference potential. I have seen Chinese copies that look really good on the outside, but when tested show very poor radiation patterns.