Someone at our airport runs the VXA720 from 20 Kms away in a shed and that picks up traffic well including those in the circuit, but not from late final. You possibly may not need an external aerial.
The VXA 220 has two voltage input sockets - one that charges the battery and one that only charges the head unit so no issues with frying the battery.
My other radio is a Vertex Standard VXA 710 - take a look, an attractive unit with lots of features including VOR, fm radio and led strobe... BUT the speaker is next to useless and sounds like it's software based versus the old-school sound of the 220.
The Vertex models are all fully waterproof too which we proved on one occasion accidentally.
(I don't work for Vertex. I also bought a Marine VHF off them too which works very well, much better than the Chinese imported ones everyone is getting around with these days)
Hopefully one day the regulators will catch up when they realize how many of these are actually being imported.