A Citizens Band (CB) radio is a type of two-way radio that allows for communication between individuals over short distances, typically within a range of a few miles. CB radios operate on a specific frequency band, which in the United States is the 11-meter band (26.965 MHz to 27.405 MHz).
CB radios use Amplitude Modulation (AM) to transmit and receive signals. In AM, the amplitude (or strength) of the radio wave is varied to carry the information (voice, data, etc) being transmitted. The signal is received by a CB radio’s antenna, which converts the radio waves into an electrical current. The electrical current is then passed through a tuner and a demodulator, which separate the information from the carrier wave. The signal is then amplified and sent to the speaker, allowing the user to hear the transmission.
FM (Frequency Modulation) is a method of transmitting and receiving signals that is different from the traditional AM (Amplitude Modulation) used by most CB (Citizens Band) radios. In FM, the frequency of the radio wave is varied to carry the information (voice, data, etc) being transmitted.
One of the main advantages of FM over AM is that FM is less affected by noise and interference. In AM, any noise or interference that is present on the same frequency as the signal will be amplified along with the signal, making it more difficult to understand. In contrast, in FM, noise and interference are less likely to affect the signal because they do not cause changes in the amplitude of the carrier wave, but only in its frequency.
Another advantage of FM is that it is more efficient in the use of the available bandwidth. This is because the FM signal can be transmitted using a narrower bandwidth, which allows for more information to be transmitted over the same frequency range.
Despite the advantages of FM, most CB radios use AM due to its simplicity and lower cost. FM CB radios are available, but they are less common and typically more expensive.
It’s also important to note that FM is not allowed for CB radio usage in the United States and other countries, as the FCC only permits the use of AM for CB transmissions.
In other countries, the regulations regarding the use of FM for CB radio transmissions may vary. For example, In Australia, the use of FM is permitted on the CB radio band, and in fact, most of the radios that are sold there are FM. In the UK and Europe, the use of FM is also allowed for CB radio transmissions.
The process is reversed when transmitting, where the microphone converts the user’s voice into an electrical current, which is then modulated onto a carrier wave at the appropriate frequency. The modulated signal is then sent out through the antenna, allowing it to be received by other CB radios tuned to the same frequency.
In CB radio there is also SSB mode – user can transmit and receive on the upper and lower sidebands. SSB mode is also known as “12 watts SSB” or “Sideband” mode. It is important to note that SSB radios require a more accurate tuning to properly receive a signal, and the received audio may sound different from what you’re accustomed to hearing from an AM radio.
CB radios have a simple push-to-talk (PTT) mechanism, which allows users to transmit and receive messages. When the PTT button is depressed, the radio transmits a signal on the designated frequency, allowing the user to speak and be heard by other CB radios on the same frequency. When the PTT button is released, the radio switches to receive mode, allowing the user to hear messages from other users on the same frequency.
It’s worth noting that CB radios are limited in power output, which affects the range of communication, and that certain channels or frequencies may be restricted for certain types of use. It’s important to check with the Federal Communications Commission (FCC) or a local authority to ensure that you are operating within the legal limits and regulations in your area.