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- Continuous wave (CW) - an electromagnetic wave of constant amplitude and frequency, typically a sine wave.
- Modulated continuous wave (MCW) - most often used by repeaters for identification. Morse code telegraphy, transmitted using an audio tone to modulate a carrier wave. MCW is commonly used by RDF beacons to transmit the station identifier.
- Frequency-shift keying (FSK) - a frequency modulation scheme in which digital information is encoded on a carrier signal by periodically shifting the frequency of the carrier between several discrete frequencies. The technology is used for communication systems such as telemetry, weather balloon radiosondes, caller ID, garage door openers, and low frequency radio transmission in the VLF and ELF bands. Dots and dashes are transmitted as different frequency continuous waves, for easier reception in noisy conditions. The simplest FSK is binary FSK (BFSK, which is also commonly referred to as 2FSK or 2-FSK), in which the carrier is shifted between two discrete frequencies to transmit binary (0s and 1s) information.
- Amplitude modulation (AM) - a modulation technique used in electronic communication, most commonly for transmitting messages with a radio wave. In amplitude modulation, the amplitude (signal strength) of the wave is varied in proportion to that of the message signal, such as an audio signal. This technique contrasts with angle modulation, in which either the frequency of the carrier wave is varied, as in frequency modulation, or its phase, as in phase modulation.
- Double-sideband suppressed carrier (DSB-SC) - transmission in which frequencies produced by amplitude modulation (AM) are symmetrically spaced above and below the carrier frequency and the carrier level is reduced to the lowest practical level, ideally being completely suppressed.
- Independent sideband (ISB) - an AM single sideband mode which is used with some AM radio transmissions. Normally each sideband carries identical information, but ISB modulates two different input signals — one on the upper sideband, the other on the lower sideband. This is used in some kinds of AM stereo (sometimes known as the Kahn system).
- Single sideband (SSB) - or single-sideband suppressed-carrier modulation (SSB-SC) is a type of modulation used to transmit information, such as an audio signal, by radio waves. A refinement of amplitude modulation, it uses transmitter power and bandwidth more efficiently. Amplitude modulation produces an output signal the bandwidth of which is twice the maximum frequency of the original baseband signal. Single-sideband modulation avoids this bandwidth increase, and the power wasted on a carrier, at the cost of increased device complexity and more difficult tuning at the receiver. It comes as an upper sideband (USB) or lower sideband (LSB).
- Compatible sideband transmission - also called amplitude modulation equivalent (AME) or Single sideband reduced-carrier (SSB-RC), is a type of single sideband RF modulation in which the carrier is deliberately reinserted at a lower level after its normal suppression to permit reception by conventional AM receivers. The general convention is to filter the lower-sideband, and communicate using only the upper-sideband and a partial carrier.
- Frequency modulation (FM) - the encoding of information in a carrier wave by varying the instantaneous frequency of the wave. The technology is used in telecommunications, radio broadcasting, signal processing, and computing.
- Phase modulation (PM) - a modulation pattern for conditioning communication signals for transmission. It encodes a message signal as variations in the instantaneous phase of a carrier wave. Phase modulation is one of the two principal forms of angle modulation, together with frequency modulation.
- Radiofax - an analogue mode for transmitting monochrome images via high frequency (HF) radio waves. It was the predecessor to slow-scan television (SSTV). It was the primary method of sending photographs from remote sites (especially islands) from the 1930s to the early 1970s. It is still in limited use for transmitting weather charts and information to ships at sea.
- Amateur teleprinting over radio (AMTOR) - a type of telecommunications system that consists of two or more electromechanical teleprinters in different locations that send and receive messages to one another. AMTOR is a specialized form of RTTY protocol.
- D-STAR (Digital Smart Technologies for Amateur Radio) - a high speed (128 kbit/s), data-only mode; a digital voice and data protocol specification for amateur radio. The system was developed in the late 1990s by the Japan Amateur Radio League and uses minimum-shift keying in its packet-based standard. There are other digital modes that have been adapted for use by amateurs, but D-STAR was the first that was designed specifically for amateur radio.
- Hellschreiber - also referred to as either Feld-Hell, or Hell a facsimile-based teleprinter; a facsimile-based teleprinter.
- Discrete multi-tone modulation modes such as Multi Tone 63 (MT63) - also known as orthogonal frequency-division multiplexing (OFDM); a type of digital transmission used in digital modulation for encoding digital (binary) data on multiple carrier frequencies. OFDM has developed into a popular scheme for wideband digital communication, used in applications such as digital television and audio broadcasting, DSL internet access, wireless networks, power line networks, and 4G/5G mobile communications.
- Multiple frequency-shift keying (MFSK) - modes such as FSK441, JT6M, JT65, and FT8; a variation of frequency-shift keying (FSK) that uses more than two frequencies.
- Olivia MFSK - an amateur radioteletype protocol, using multiple frequency-shift keying (MFSK) and designed to work in difficult (low signal-to-noise ratio plus multipath propagation) conditions on shortwave bands. The signal can be accurately received even if the surrounding noise is 10 dB stronger. It is commonly used by amateur radio operators to reliably transmit ASCII characters over noisy channels using the high frequency (3–30 MHz) spectrum. The effective data rate of the Olivia MFSK protocol is 150 characters/minute. A digital mode that is directly derived from Olivia is called Contestia.
- JS8 - an amateur radio QSO communication mode based on FT8.
- Packet radio (AX25) - the application of packet switching techniques to digital radio communications. Packet radio uses a packet switching protocol as opposed to circuit switching or message switching protocols to transmit digital data via a radio communication link.
- Amateur Packet Radio Network (AMPRNet)
- Automatic Packet Reporting System (APRS)
- PACTOR (AMTOR + packet radio) - a radio modulation mode used by amateur radio operators, marine radio stations, military or government users such as the US Department of Homeland Security, and radio stations in isolated areas to send and receive digital information via radio. PACTOR is an evolution of both AMTOR and packet radio.
- Phase-shift keying (PSK) - a digital modulation process which conveys data by changing (modulating) the phase of a constant frequency carrier wave. The modulation is accomplished by varying the sine and cosine inputs at a precise time. It is widely used for wireless LANs, RFID and Bluetooth communication; examples include 31-baud binary phase shift keying (PSK31), 31-baud quadrature phase shift keying (QPSK31), 63-baud binary phase shift keying (PSK63), 63-baud quadrature phase shift keying (QPSK63).
- Radioteletype (RTTY) Frequency-shift keying - a telecommunications system consisting originally of two or more electromechanical teleprinters in different locations connected by radio rather than a wired link. Radioteletype evolved from earlier landline teleprinter operations that began in the mid-1800s. In some applications, notably military and government, radioteletype is known by the acronym RATT (Radio Automatic Teletype).
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