When you hear that the opposing team planted a beacon and you are just wondering around the base doing nothing with basic inf, turn into an engy, walk around the buildings until you hear the beeping noise and then get closer to it and it will get louder. When you see it make a quick team chat (F3) saying what buildings its at (ex. "beacon at ref") and then proceed to disarm it by aiming repair gun at it (hotwires and techs will disarm way faster) until the energy is gone, you will recieve 300 points also so its worth it. Also there will usually be a stealth black hand guarding it so you may also want to include this in a chat if you die from it while attempting a disarm (ex "blackhand guarding beacon") - This will mostly save you the game or at least the building.
-So many times after a beacons deployed I see 3-5 newbies standing still with regular solders when they could be helping to disarm the beacon and I am frantically trying to disarm it.