So CB "citizens band" basically low frequency AM "Amplitude Modulation" It is authorized 40 channels between 26.965 MHz and 27.405 MHz. There is sort of more channels if your radio can do side band. Legal output power is 4 watts. For emergency use I would recommend a walkie-talkie with a rubber ducky antenna, to start. If you get into it move on to better antennas base station and linear amplifiers and swr meter. Look for a walkie-talkie with 40channels and a digital channel display. Should be cheap. Cobra makes some good radios. Car radios are ok but you can't carry them with you like a walkie-talkie. Walkie-talkies probably have a range of 1mile or so without obstructions such as hills. That can be improved with getting to higher ground , radio tends to rain down . AM also tends to have less interference at night. Range can also be improved during solar maximum due to more power from the sun energizing the ionosphere, this is called skip.. When changing antennas swr "Standing wave ratio" matters and I'd the antenna is not tuned for the cb frequency range it can damage the radio. You can learn more by learning about swr meters. Channel 9 is the universal CB emergency channel. In most areas, it is monitored by local law enforcement at all times, so please keep random chatter off this channel. Channels 17 and 19 are commonly used channels by truck drivers. 19 is often used by drivers going east or west; 17 by drivers going north or south. Hope this helps!