Tired,Here we are eleven years later and RKO's signal is still crappy, SMH.
From what you describe of WRKO's night time signal in your area, it may not be the fault of the antenna pattern or any RF (radio frequency) problem, but COULD be the result of sloppy control of audio levels. These, as you know, are controlled by that smooth operating automation whiz box at iHeart Central in Medford. Remember, no one is monitoring what's going out over the air, except for us schmucks, er, listeners.