Hi Jon, I sspect you're getting good reception of the a/c as they're up in the air, whereas there's obstructions (hills, buildings, trees or whatever!) between you and the ground stations. I'm lucky down here on the Lizard in Cornwall, as I pick up the relayed AM transmissions from London ATC on VHF. The main problem is these signals are really "line of sight". Any exterior antenna should improve the signals being received. The Diamond D-777 is a cracking antenna, but you can only receive what's reaching the antenna - pre-amps are definitely the "panacea or cure-all" that they're portrayed to be. Height is primary and a pre-amp can overcome the losses caused by longer lengths of co-ax, but will not necessarily improve things. Looking at your question again Jon, you may well be able to get away with an exterior D-777 antenna, as they're not huge or very noticeable - look more like a pole............