Hi
I am looking for the best antenna that I can mount on my car (does not need to be magnetic). I listen to Aircraft in the 112-135 range and also EMS in the 412 - 470 Mhz range.
The Larsen NMO 150/450/800 is a very good antenna for the ranges you want to listen to. It's only about 16 inches tall, with an added two inches if you use a mag mount. Reasonably priced, well built, and does a great job on everything above 108 Mhz.
This is what I used in my truck. Valor PDC64 Car Antenna Coupler I know it's discontinued but, there are others out there that do the same thing. You'd have to check on the Internet.
I didn't have to drill another hole, already have 6 on my truck. Just used the truck radio antenna and since it's only for listening, seems to work great with my BC780xlt all the way from the CB to 1.2 ghz ham band with no noticeable degradetion.
As a matter of info. I don't have a AM/FM radio in my truck. I used the radio hole to mount my scanner and a 6m ham radio. I use one end of the splitter for the scanner and the other for my 7" digital TV mounted below my laptop.
Works very nice for both.
This is the install from start to finish if you're interested in taking a look.