How do I know what antenna to use?

I received the quote for the UHF Lo-Profile antenna.

Next question is can they be mounted in any position... Vertically instead of the usual horizontal position?
How would it perform if it was mounted inside the car?

Thx.

Best to mount it horizontally as that will give vertical polarisation which is what other vehicles will be using. You can mount it anywhere you like but the normal rules apply: best performance is obtained when it is high and clear, so on top of the vehicle is the place to go. The lower and more obstructed it is, the worse the performance. Of course this will not be an issue if you are only after short range comms. But if you are going to do that then maybe you should save money and just go for a ground plane independent antenna and camouflage it (back to the hat over the antenna idea).

Howard