You will encounter many different ideas here, but most will agree that an NMO-mount antenna in the center of the vehicle roof is your best option. Personally, I have nothing against mag-mounts, and even , in some cases, through the glass antennas, but others have differing opinions. A trunk-lip mount can be very effective if you get it well grounded, and it will work on the hood as well as the trunk.
If you intend to keep the triband functionality of the radio, that limits your choices somewhat. Diamond and others make triband mobile antennas that should serve you well. Diamond's CR320BNMO ought to do fine.
The biggest concerns I have with using an HT mobile are antenna connections, power, and audio. If you don't already have one, get a speaker mike for it. That may solve a lot of problems, as the speaker in the handmike can be clipped on closer to your ear when driving - when using an HT in the car, I clip mine on my shirt pocket, and that works fine. You will want a DC cord to run the HT while mobile, and an adapter to connect from the SMA connector on the radio to the coax from the antenna. I prefer the flexible type as they don't put as much stress on the HT connector.
Now, if you don't already have these things, I bet you can get a new monoband mobile radio for less than the cost of these add ons and have at least 50 watts instead of 5. It's something for you to consider. You also save wear and tear on the HT antenna connector that way. http://www.universal-radio.com/catal...xvrs/1900.html
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