Back about 20 years ago – in the ice age before the first shoebox-sized cellphones – there was quite a fad of regular people using CB radios. They were like Ur-cellphones crossed with proto-chatrooms: perfect strangers chatting merrily while on the road.
Do they still exist? Does anyone use them? Or have cellphones completely replaced them?
They are still around.
A couple of years ago, I spent some time on the Washington (DC) Beltway at Rush Hour in a truck with a CB. LOTS of talk, many people with line boosters illegally increasing their power. Some with other modifications to do voice distortion.
Anyway, not the old spirit of cooperation of calling out traffic obstructions and all that. Just ‘rag- chewing.’
Like you said, they were a fad for most people that died out well before mobile phones became popular. Even REACT, a group that used channel 9 to help people out seems like it’s all but dead, and I have heard a lot of non-emergency traffic on channel 9. CBs are still sold and in use, but mostly by truck-drivers. There are still some people who have base and/or mobile stations and talk to each other locally and over longer distances by ionospheric skip. As far as local communication goes, they’re pretty useless. I have one that I hooked up to an antenna I use for cross-country as well as local communication; it didn’t do too well, and it didn’t do too well on a vertical antenna 20ft off the ground.
Disclaimer: I spend most of my time on amateur radio bands, so I am not that much in touch with the CB world. This is my impression from infrequent use of my CB in my car and research on the web. I invite corrections and updates.
Vlad/Igor
I recently bought a CB linear amp at a yard sale just to get it off of the streets. I will get around to testing it to see if it has the specs to be used on the amateur 10 meter band. I’m not holding my breath, though.
Vlad/Igor
Most linear amps for 11-meters are broadbanded enough to do well on 10 meters. The thing you gotta watch out for is poor harmonic suppression, which CB linears are notorious for.
To my knowledge, CB linear is an oxymoron. 
CB was never allowed more than 5W output, unless you’re talking about single sideband. Those folks who did use linear amplifiers were misapplying a device designed for use by Ham operators. Had they been legal, I’d have sold a thousand of them when I worked for ahem Lafayette Radio Electronics. There’s a name you haven’t heard in close to a quarter century. 
Certain (non trucker) groups of people still use them…I’m in a few Corvette CLubs and they help greatly in handling caravans during driving events…
SCCA will typically use a base station and a half dozen handhelds to handle track communications too.
Given the technical chops of some CBers I’ve heard (“Hey, turn down your squelch, I can’t understand you [as the other guy overmodulates and causes splatter]”), if they find any kind of amplifier they’ll think about putting it in line. Legally, CBs are limited to 4 watts, which only carries a few miles without skip, but I’ve heard of some CBers boosting their signal to 100+ watts for more range. The amp I have is really dinky, and probably only puts out perhaps 20W or so. As Q.E.D. points out, I have to make sure that the spectral output is within FCC specs before I try it on the air.
Vlad/Igor
Mobile CB’s have limited range, and are falling out of favour to UHF and VHF for working purposes. I still have a CB, but only use it to monitor CH 19 on long highway trips, to keep apprised of truck traffic, accidents ahead, etc.
My VHF is a much more useful communication tool.
My uncle uses his for communication while hog hunting. Feral pigs.
No, really. You should see the trophies. Just the jaw-tusk bit. It’s actively creepy.
100 watts? Try 600 or 1000 watts. Hell, I had a 225W amp and was regularly talked over. I didn’t use it often, only when shooting skip, but I did have one (talked to Australia once ;)).
I actually still have my old radio… it’s stickly against FCC rules also. Dual power settings (5W or .5W), 240 channels (including much of the 10 meter band), can transmit in AM or FM, built in reverb and echo… well you get the idea… It just sits on a shelf in my house, I have no plans on ever using it again.
I know a guy that had some crazy power like that in his vehicle. You could take a florescent bulb (4 footer), and hold it next to the antenna, when keyed up, it would light up!
My Dad owms a CBH, & has owned several since the 70’s.
He’s been a salesman, & still travels by car a lot.
Keeps him from being lonely.
I do the same thing. I have a CB on Ch 19, plus a dual-band amateur radio (VHF/UHF) that puts out 50W and 30W respectively. Without a repeater, the dual-band radio goes further than the CB at 4W. Getting an amp for the CB wouldn’t help, for all of the heterodynes and the short antenna.
CB radios are good for short range communication, but the UHF FRS radios are giving them a run for their money. Even a UHF GMRS radio will do a better job, if only because there is a better match between the transmitter and antenna.
Vlad/Igor
KF4VCC