Affordable 27 MHz CB Radio Transceivers
CB or the Citizens Band Radio Service is where the FCC allows untrained and unlicensed individuals to use low-powered two-way radios radios for personal or business use.
CB radios are limited to a power output of 5 Watts AM or 12 Watts PEP (in single sideband/SSB mode). These 2 way radios operate in the 27 MHz HF (shortwave) band, and people using them are only permitted to talk to others within the United States. No overseas (DX) contacts are allowed. The CB radio service has 40 channels assigned to it. Since each channel can be used in AM mode or as USB (upper sideband) or LSB (lower sideband) in single-sideband mode, some folks like to imagine they have 80 or 120 channels. But that's not quite right.
Single sideband transceivers (SSB two-way radios) cost more than AM transceivers because they use more complex circuitry, and they take a little more skill to operate properly. In return, the SSB radio signals will almost always 'get through' over longer distances, and in poorer atmospheric conditions than an AM signal can manage.
Ham Radio (officially called the Amateur Radio Service) is where people who have studied two-way radios, antennas and US and international regulations - and who have passed an examination (and paid a fee) are allowed to communicate with other radio hams in their own country and with other licensed radio hams around the world.
Ham Radios (Amateur Radio equipment) can range in power from less than 1 Watt to 1000 Watts, and it isn't the equipment that gets licensed... It is the person operating it. Most handheld ham radios would be 5 Watts or less, but mobiles are usually between 10 and 100 Watts, most HF amateur radio base stations are 100 or 200 Watts, and hams are allowed to use linear amplifiers that give them up to 1000 or 2000 Watts of power.
On top of this, Amateur Radio Operators (Hams) are permitted to use large antennas on towers that may be 30 feet, 50 feet or higher in the air, plus all kinds of fancy sophisticated antenna systems to send out a highly directional transmitter beam. Like yagi or quad antennas.
Why do radio Hams have all these privileges that CBers do not? It comes back to the licensing and the expertise that Hams/Amateur Radio Operators study for. They are supposed to have the skills to set up and operate their two-way radio hobby, and to do it without causing any radio interference to their neighbors or to other radio users.
Amateur Radio operators also have to know how to handle emergency radio traffic, which is admittedly quite rare. (It seems to happen much more in the movies.) Licensed Hams are taught not to interfere if distress traffic is taking place. One takes control, and the others know to shut up and just listen. But that is another subject.