Greets; Back Story; Had a K40 C.B. antenna, and located just a few feet back from the top of the windshield, and it's base was magnetically held in place on the mid-line. I had drilled a hole in order to run the antenna lead/cable through the roof, and connect the other end to the radio. For theft protection it was easy-peasy to hop up, and twist/remove the antenna off from it's base, leaving the magnetic base in it's position, and swinging the antenna down, and around in order to place it on top of the dash-board, and visa-versa. The unit was '70's Radio Shack 4w, (tuned up, he-he), and worked superbly together. Today there are some who go through, and rebuild units known for reliably, (in their day). Search Google. More modern stuff.., I dun'no, but there's some units tweeked in Asia, or built differently, that are in all appearance the same labeled model number sold in our Country.., can't remember the details, but they are special, and might be found say eBay, etc; Google.
As touched upon regards the 'ground-plate; the location of whatever antenna you use is important. Picture a big circle around a more centrally located antenna, (such as mentioned above), and that's it's zone, and it projects the radio transmission equally forward, and rearward, and kind of sort of deep into the left, or right sides of the vehicle. Basically the central collection of vehicles can reach both the lead, or rear vehicle.., and everyone else in the middle, of course..! Frontal location works like a headlight beam which is useful if one is in the rear of a convoy wanting to reach everyone out to the lead vehicle. Rear location does that in reverse, i.e., projecting transmission of the radio signal way, way rearwards, and is best for the leading vehicle in order to reach over back to the rear of a convoy. Lead=rear mount. Middle=middle mount. Rear=forward mount. Sometime one sees a corner mount, but again the field pattern would be either of 4 directions diagonally away from the vehicle, i.e., forward to the left, or right, or reward to the left, or right.., not within the same zones as those mounted along the mid-line, i.e., front, middle, rear.
Consider what ever placement you require, and become acquainted with the hand-held SW Meter in order to 'trim' the length of your antenna's balance with your set. Google fer'sho. This task is better done around other C.B.'ers, some distance away in you area, but never, ever one in a vehicle thats just nearby, i.e., just yards, and yards away.., everybody communicating through their sets. I recall some asses would key up their mics in order to blow out nearby radio sets, (back in the day of Dixie 200 watt aux./amps). Anyway, I would imagine good sets/antenna's would have some documented suggestions about using the SW Meter, etc.
Direct positive, and negative leads can go directly, (from your set), to your battery posts, or some purists might choose a different grounding spot.., but what's cool is that you will minimize any rpm static coming through the set, which can be an annoyance at least, but a major detriment in attempting to hear a transmission, etc. A.M. radios also like the more direct connection. Or you can obtain noise filters for either.
From what I recall one can now operate a C.B.Radio without any kind of license. Groovy. However there are so many other types of radios that are more reaching, but who's to listen if the local network is just C.B. Fishing boats don't really demand C.B. radios, but some have every possible kind, including C.B. Trucker's often have multiple radios too. Safety is a big consideration, and as mentioned by those chiming in.., the terrain is a factor.., but other license requirement radios provide honking transmissions, and reception capabilities. In my area of Alaska, not so much C.B., but there are some mobile, and some base stations. There are a lot of other types that reach further, as previously mentioned. I have noticed that a lot of the C.B.'ers have let their equipment collect dust, and use cell phones in, and around civilization, lol.
There are different kinds of hand-mics, and that's another trip, lol, google again. I used a K40 mic, and K40 antenna with my Radio Shack. Anyways it's, (like been said), sort of a hobby thing, but if you have a fad going on in your area.., cool.
The above 3 cents is not intended to provide any expert knowledge.., just my memory lane thing, lol, rambling, lol.
Happy Trails.