A radio frequency (RF) transceiver is a device that can both send and receive radio signals. An RF transceiver combines the functions of both a transmitter and a receiver. Common devices that contain RF transceivers include citizens' band (CB) radios, walkie-talkies, cordless phones, cellphones and computers that are capable of using a wireless network.
In an RF transceiver, the tasks of both receiving and transmitting radio waves are accomplished by common circuitry and components. When functioning as a receiver, an antenna captures the radio waves, a tuner isolates the wave of the desired frequency, and a detector or demodulator extracts the information from the wave. When functioning as a transmitter, the circuits of the transceiver generate a continuously varying current. The current is then modulated to include the information signal. The modulated sine wave is then passed along the antenna and transmitted as a radio wave.
The type of transceiver varies depending on the type of modulation that will be used to communicate information. Pulse modulation (PM) is the simplest way to communicate using radio frequencies. To achieve PM, the electric circuit is opened and closed, turning the sine wave on and off. PM is the basis for communicating by Morse code.
Amplitude modulation (AM) modulates the amplitude of the sine wave to carry information. AM radio was the first to be developed by broadcasting stations. It can be detected by simple equipment and has a greater range of transmission, but it does suffer from interference. AM radio is broadcast over the part of the radio spectrum called medium frequency (MF).
Frequency modulation (FM) modulates that frequency of the sine wave to carry information. FM radio is higher fidelity, suffers less from interference than AM radio and became the dominant broadcast medium during the 20th century. There is more bandwidth required by FM radio, so it is broadcast in the part of the radio spectrum called very high frequency (VHF).
Frequency-shift keying (FSK) is an example of a modulation for digital data. It translates the 1s and 0s of binary code into radio waves. Other types of digital modulation include phase-shift keying (PSK), amplitude-shift keying (ASK) and quadrature amplitude modulation (QAM).
Beyond modulation type, RF transceivers vary according to their operating frequency, such as MF, VHF, high frequency (HF) and ultra high frequency (UHF). Other relevant technical specifications that are useful when comparing RF transceivers include transmission distance, output power and data rate. Finally, a major difference in RF transceivers is whether they are designed to be mobile and handheld.
A great way for a person to learn more about RF transceivers is to become an amateur radio operator, or ham. An amateur radio license allows hams to operate on designated amateur radio bands. Many countries have a standard amateur radio licensing procedure that usually involves some coursework and a licensing exam.
Many hams enjoy building their own radio rigs, including RF transceivers. An RF transceiver can be built from scratch or from a kit. Purchasing a pre-assembled, low-end RF transceiver is also a good way to learn before one moves on to more expensive and advanced equipment.