Let's go over FRS first.  These little handhelds came onto the market just a few years ago.  The Family Radio Service is designed as a no license, personal use radio system with limited range.  They have 14 channels, can be tone encoded for privacy and are relatively inexpensive.  While Libby and I have a pair of tiny ham radios for personal communications, we have also purchased a pair of FRS radios, so we can communicate with non ham friends in campgrounds etc.

There is a more powerful version of FRS which requires a license.  The difference in these radios is not much and the expense of the radios is not worth the increased range, which is minimal at best.

FRS is great for backing the rig  into a spot, keeping in touch at a rally or in Home Depot (Libby is always stopping to play with things)  I suggest that you use the tone encode function (CTCSS or Code Tone Controlled Squelch System) for one channel that you and your partner use for private communications.  That way, you run less chance of interfering with someone else and less chance of being interfered with on the channel you choose.  As an example, we use channel 2, CTCSS 12.  That way, only those folks who use this exact same channel and CTCSS tone will be able to hear us and vice versa.  You can pick any channel and CTCSS tone you wish.  (On our ham radio walkie talkies, we do the same thing with 146.48 MHZ and  107.5khz as the CTCSS tone)

CB radio is more useful in situations where your rig is moving down the road.  Since FRS has a limited range, say a mile or so at maximum, CB is the radio of choice for communicating on the road with other RVers and other folks.  While you can learn some exceptionally colorful vocabulary by listening to Channel 19,  you can also get lots of good road info by listening in on the truckers.  They have saved our bacon a number of times, getting us out of traffic jams and around accidents.

The radio is probably the least important component of a CB system, the antenna is the most important.  You can have a $500 radio and a poor antenna and you will get poor results.  You can have a cheap radio (mine cost $35 at WalMart) and a good antenna and be very satisfied with your ability to communicate.   The best place to mount your CB antenna is in the middle of the roof of your rig, but this isn't too practical in most cases.  The second best place is on the road side of your rig as high as you can get it without hitting bridges and limbs.  The worst location is on the curb side of your rig.  This is where all the low signs and tree limbs live.  Antennas that ride high on a rig on the curb side, have a very limited life expectancy.

Forget all the hoopla about measuring your coax, using co-phased antennas etc.  A solid antenna, coax long enough to go from the antenna to the radio and some knowledge of how the radio works, will get you on the air and communicating with skill and ease.

Brand names on antennas are not important.  Most CB antennas are either a quarter wave steel whip, a base loaded short antenna or a center loaded antenna wound on a fiberglass form.  The fiberglass has nothing to do with the antenna other than providing a solid platform for the wire to be wound around.  A quarter wave antenna on the CB band is about 102 inches.  Winding the wire around a form or forming it into a loading coil reduces the physical length, while producing an electrical length appropriate to the CB band.  Many center loaded fiberglass wound antennas are 48 inches and our base loaded whip is much shorter.
 

Base Loaded                         fiberglass center load        co phased                            bent antenna syndrome
 

I believe that the maximum height allowed for anything sticking up from a moving vehicle is 13 feet 6 inches.  Keep your antenna below that height.  In fact, it would be a good idea to keep it pretty close to the maximum height of whatever else is on your roof.  That way you won't become a poster child for the curled antenna syndrome.  NOTE  see the springs on the fiberglass whip. Its a real good idea, since not all tree limbs live on the curbside of the road.  The co phased antennas on the MDT will work on both MDT and Motorhomes, but they give a radiation pattern that looks like a figure 8.  Good lobes to the front and rear and lesser ones to the sides.  That's ok if you are going down a straight road in Nevada with no turns for 100 miles.  If your traveling buddy has rounded a curve in front of you or you are around a curve in front of him/her, guess what, you actually get less signal to the person you are trying to communicate with.  A single, well placed antenna should actually do better than co phased whips unless you are driving on a drag strip.  Truckers  don't believe this, but you cannot change the  laws of radio propagation.

To use the radio, simply turn it on and tune the appropriate channel.  Channel 19 is the most common for truckers around most of the country, 13 is a common RV channel and channel 9 is the emergency channel.  All the others are fair game.  If you have a friend traveling with you, contact them on 13 or 19 and move to another channel.  There is no reason to clutter up 19 with your chatter when you could be on a less used frequency.

Turn the volume up to a comfortable listening level and turn the squelch to just cut out the background noise.  If you are traveling close together, you can tighten the squelch even more to cut out others who are further away but on the same channel.  If you cannot hear your traveling companion, the two most common problems are, the volume is turned down or off or the squelch is set too tight (high) and you are not able to copy their transmission.

CB jargon is ok if you really get turned on to that sort of thing, but plain English, or whatever language you choose to speak works a lot better.  10-4 good buddy is more easily expressed by "ok" or "I understand".  Instead of calling Breaker 13, just call your friend by his name or coach type.  Handles (funny names) are popular on CB, but not necessary.  In ham radio, we use the licensed call sign for that station.  As an example, my callsign is KE4D and Libby is KB4FFO.  These are just like the callsigns your local tv or radio station is assigned by the FCC.  In the U.S. ham radio callsigns begin with N, K, A or W.  CB used to have assigned callsigns, but those went the way of the wild dogs back in the 70s when the CB craze got out of control.   Now, one can just say "Rich, are you there?".   Of course, if Rich is not there, don't expect him to answer.  Our friends the Holders have an 11 year old son.  Tommy has decided that his CB handle is the Sunflyer Kid after their model of Itasca RV.  When Tommy calls me, he just says, John, do you copy?  It all works.  If you really want to jump into the CB jargon, knock yourself out.  I prefer plain English.

You don't have to shout at the mike any more than you do a cell phone.  Yes, people do both, but it is not necessary.  In fact, most folks talk too closely to the microphone and are distorted at the receiving end.  Most of the time, this is caused by over modulating the radio.  Just speak in a normal tone of voice and keep the mike about 3 to 5 inches away from your mouth.  In fact, you can talk across the microphone and avoid all the breathy stuff that you sometimes here on the radio.  Stay away from reverb units.  Many truckers like to use these things and for the life of me, I cannot understand why.  It makes them much more difficult to understand.

Never use channel 9 for anything other than a bona fide emergency.  Remember that today, before you can report on your radio, someone will have probably already done so with a cell phone.  I'm not saying you shouldn't report emergencies on channel 9, but don't get an accident trying to do so.  9 times out of 10, the cell user has already done it.  If you need to report an emergency, pull off the road so you can describe what is needed or what happened without having to think about dodging other vehicles or people in the road.

Now a plug from our sponsor.  If you really want to have a great communications system, get your Amateur license.  The beginning license is called a Technician and requires no morse code.  The other two classes of ham radio license require more comprehensive written exams and a 5 word per minute morse code test.  It has become fairly easy to become a ham.

Have fun and good communicating.