citizens band

The part of the spectrum dedicated by the US Federal Communications Commission to unlicensed radio transmissions, mostly among truckers. Also known by its initials, CB.

There are 40 channels on CB radio. Channel 9 is reserved for emergencies only. Channel 19 is the most general forum, where most people hang out. Private conversations belong on other channels, although of course privacy consists of other people's willingness to shut up on a channel that's in use and not to eavesdrop. Newbies who don't speak CB lingo, or speak a 70's dialect, might be told to take it to channel 41. The assumption is that they haven't yet learned there are only 40 channels.

The official CB channels are:

Channel   Frequency    Common Use 
     
1          26.965 MHz 
2          26.975 
3          26.985  Unofficial Marine Channel 
4          27.005 
5          27.015 
6          27.025 
7          27.035 
8          27.055 
9          27.065  Emergency/Traveler Assistance 
10        27.075 
11        27.085  Old Official Calling Channel 
12        27.105 
13        27.115  Unofficial Marine Channel 
14        27.125  Very Common Walkie-Talkie Channel 
15        27.135 
16        27.155  Old SSB Channel 
17        27.165 
18        27.175  Old SSB Channel 
19        27.185  Truckers Channel 
20        27.205 
21        27.215 
22        27.225 
23        27.255  Shared with Radio Control Devices 
24        27.235 
25        27.245 
26        27.265 
27        27.275 
28        27.285 
29        27.295 
30        27.305 
31        27.315 
32        27.325 
33        27.335 
34        27.345 
35        27.355  SSB 
36        27.365  SSB 
37        27.375  SSB 
38        27.385  SSB 
39        27.395  SSB 
40        27.405  SSB 

There are also the "freeband" channels that run from 26.000 MHz up to CB channel 1, and from channel 40 up to the low end of the 10-meter ham band (28.000 MHz). It is illegal to operate on these frequencies, but FCC enforcment is pretty lax.

Maximum power on the citizens band is 4 watts for amplitude modulation (AM) mode, and 12 watts peak envelope power for single-sideband (SSB) modes. Channels for SSB use are designated by informal agreement. All modes are legal in all channels, but you will get flamed crisper than a slashdot karma-whore for using the "wrong" mode for that channel.