Modes of communication
Amateurs use a variety of voice, text, image, and data communications modes over radio. Generally new modes can be tested in the amateur radio service, although national regulations may require disclosure of a new mode to permit radio licensing authorities to monitor the transmissions. Encryption, for example, is not generally permitted in the Amateur Radio service except for the special purpose of satellite vehicle control uplinks. The following is a partial list of the modes of communication used, where the mode includes both modulation types and operating protocols.
Morse code is the original digital data mode. Radio telegraphy which is the direct on/off keying of a continuous wave carrier by Morse code symbols, often called amplitude-shift keying or ASK, may be considered to be an amplitude modulated mode of communications. Although more than 140 years old, bandwidth efficient Morse code, originally developed by Samuel Morse and Alfred Vail in the 1840s, uses techniques that were not more fully understood until much later under the modern rubrics of source coding or data compression. The bandwidth efficiency of Morse code arises because the most used source symbols were accorded the shortest Morse code symbols and the least used were accorded the longest symbols by Vail and Morse. Vail and Morse intuitively understood bandwidth efficiency in code design. It was not until one hundred years later that Claude Shannon’s modern information theory (1948) put Morse and Vail’s Morse code technology on a firm theoretical mathematical footing, that then resulted in similar Morse code-like bandwidth efficient data encoding technologies such as the modern Huffman, Arithmetic and Lempel-Ziv codes. Morse code is still used by amateur radio operators. Operators may either key the code manually using a telegraph key and decode by ear, or they may use computers to send and receive the code.
- Continuous wave (CW)
- Modulated continuous wave (MCW) is most often used by repeaters for identification.
- Frequency shifting continuous wave (FSCW) dots and dashes are transmitted at different frequencies for easier reception in noisy conditions.
- Prosigns for Morse code (prosigns)
Decades after the advent of digital amplitude-shift keying (ASK) of radio carriers by Morse symbols, radio technology evolved several methods of analog modulating radio carriers such as: amplitude, frequency and phase modulation by analog waveforms. The first such analog modulating waveforms applied to radio carriers were human voice signals picked up by microphone sensors and applied to the carrier waveforms. The resulting analog voice modes are known today as:
- Amplitude modulation (AM)
- Double Sideband Suppressed Carrier (DSB-SC)
- Independent Sideband (ISB)
- Single Sideband (SSB)
- Amplitude Modulation Equivalent (AME)
- Frequency modulation (FM)
- Phase modulation (PM)
Digital voice modes encode speech into a data stream before transmitting it.
- APCO P25 – Found in repurposed public safety equipment from multiple vendors. Uses IMBE or AMBE CODEC over C4FM.
- D-STAR – Open specification with proprietary vocoder system available from Icom, Kenwood, and FlexRadio Systems. Uses AMBE over GMSK with VoIP capabilities.
- DMR – Found in both commercial and public safety equipment from multiple vendors. Uses AMBE codec over a C4FM modulation variant with TDMA.
- System Fusion – Open specification with proprietary vocoder system available from Yaesu. Uses AMBE CODEC with C4FM modulation.
- NXDN Used by Kenwood (Nexedge) and Icom (IDAS)
Image modes consist of sending either video or still images.
Text and data
Most amateur digital modes are transmitted by inserting audio into the microphone input of a radio and using an analog scheme, such as amplitude modulation (AM), frequency modulation (FM), or single-sideband modulation (SSB).
- Amateur teleprinting over radio (AMTOR)
- D-STAR (Digital Data) a high speed (128 kbit/s), data-only mode.
- Hellschreiber, also referred to as either Feld-Hell, or Hell
- Discrete multi-tone modulation modes such as Multi Tone 63 (MT63)
- Multiple frequency-shift keying (MFSK) modes such as
- Packet radio (AX25)
- Phase-shift keying:
- Frequency Shift Keying:
- Spread spectrum, which may be analog or digital in nature, is the spreading of a signal over a wide Bandwidth.
- High-speed multimedia radio, networking using 802.11 protocols.
- ROS is a new Weak Signal sound card digital mode.
Activities known as modes
Certain activities in amateur radio are also commonly referred to as “modes”, even though no one specific modulation scheme is used.
- Automatic link establishment (ALE) is a method of automatically finding a sustainable communications channel on HF.
- Earth-Moon-Earth (EME) uses the Moon to communicate over long distances.
- Echolink connects amateurs and amateur stations via the internet.
- Internet Radio Linking Project (IRLP) connects repeaters via the internet.
- Satellite (OSCAR – Orbiting Satellite Carrying Amateur Radio)
- Low Transmitter Power (QRP)