Digital communications methods send information encoded as digital bits (0s and 1s) rather than as an analog waveform such as voice or continuous video. The methods listed in the question are all examples of digital modes:

• Packet radio is a well‑known digital mode that uses a radio modem to allow computers to exchange data over radio links (think of it as a radio version of a network protocol).
• FT8 is a weak‑signal digital protocol from the WSJT family (developed by Joe Taylor, K1JT) designed for reliable, low‑SNR contacts. It uses a small set of tones and short, highly structured transmissions to decode signals that would be too weak for voice or traditional modes.
• PSK31 (Phase Shift Keying, 31 Baud) is a narrow‑band digital system intended for real‑time keyboard‑to‑keyboard text conversation over HF.
• MFSK (Multiple Frequency‑Shift Keying) is a variant of frequency‑shift keying that uses multiple tones and is used by some digital systems, including certain forms of packet and telemetry links.
• IEEE 802.11 is a family of digital wireless LAN standards (often called “Wi‑Fi”) specifying digital data transmission over radio frequencies.

Because each of these is a technique for sending encoded digital information over radio or wireless links, they are all digital communications modes.

Memory aids:

• Think “digital = bits” and remember a few example names: Packet, FT8, PSK31, MFSK, and IEEE 802.11 — all are digital.

Last edited by randylimbach. Register to edit

Tags: none

FT8 is a relatively new digital mode that became popular in 2017. FT8 stands for Franke–Taylor 8‑Frequency‑Shift Keying modulation and was created by Joe Taylor, K1JT, and Steve Franke, K9AN.

FT8 was designed for weak‑signal communications and is much faster than earlier JT modes such as JT65. It is commonly used on HF bands and can decode signals that are well below the noise floor, which makes it ideal for low signal‑to‑noise operation. FT8 contacts are highly structured: transmissions are short (15 seconds) and carry a very small payload (about 75 bits) plus a 12‑bit checksum. Because of the precise timing used by the protocol, both stations must synchronize their computer clocks to a common time source (for example, via the Internet or NTP).

These technical features — 8‑FSK modulation, very short, synchronized transmissions, strong error‑tolerance and minimal information exchanges — are what enable FT8 to work reliably at low signal‑to‑noise ratios.

Last edited by brasda91. Register to edit

Tags: none

APRS (Automatic Packet Reporting System) is a two‑way tactical real‑time digital communications system for sharing information about what’s happening in the local area. Because it’s a general-purpose packet system for short, periodic updates and telemetry, it can carry GPS position reports (to show station location), short text messages between stations, and telemetry such as weather‑station data. See http://aprs.org/ for more details.

Last edited by elnicholson362. Register to edit

Tags: none

NTSC is the name of the standard used to encode colors in an analog fast-scan color TV signal.

If you ask a broadcast engineer, NTSC is sometimes jokingly expanded as Never The Same Color, because his job is to keep all the cameras looking the same. Now that TV is largely digital, the NTSC broadcast standard is much less common, but it is still used by Amateur Radio operators for analog fast-scan ATV.

Actually, NTSC stands for National Television Systems Committee, the group that defined the rules for how the broadcast signal should be encoded so televisions could display the correct picture.

Last edited by patronics. Register to edit

Tags: none

APRS stands for Automatic Packet Reporting System. It is used to transmit a station's position (usually from a GPS receiver) and other short messages so other stations can see the location and status of that station in real time. Typical components are a GPS receiver, a ham radio transmitter, and logic/interface that packages the GPS coordinates into packets for transmission.

Because APRS transmits position and status information, it is used for real-time tactical digital communications combined with maps that show the locations of stations that send APRS data.

It does not perform tasks such as counting the number of packets sent by other digital modes, providing voice over Internet connections between repeaters, or reporting how many stations are signed into a repeater.

Memory aids:

• APRS = Automatic Packet Reporting System (think "reporting" your position)
• Key components: GPS + radio + interface
• Primary use: real-time position/status reports displayed on maps

Last edited by sjvhayden. Register to edit

Tags: none

PSK stands for Phase Shift Keying. It is a method of digitally transmitting data by varying (keying) the phase of a carrier signal.

"Phase" refers to the position within the cycle of a sine wave — essentially where you are in the pattern of peaks and valleys. By changing the phase in discrete steps, different phase states can be used to represent digital information.

Memory aids:

• PSK = Phase Shift Keying (think: P for Phase)

Last edited by epicmaxi. Register to edit

Tags: none

DMR (Digital Mobile Radio) is a digital voice standard that uses time-division multiple access (TDMA) to carry two separate voice channels within a single 12.5 kHz repeater channel. Each call occupies one of two time slots, so two users can be repeated simultaneously on the same frequency without interfering with each other.

DMR is not a position-tracking system or an automatic logging technique, and it does not work by transmitting on two repeater inputs at once for error correction. Its defining feature is the time-multiplexing (TDMA) of two digital voice streams on a single 12.5 kHz channel.

Memory aids:

• DMR = Digital Mobile Radio
• Think "two slots in one channel" — DMR uses 2-slot TDMA on a 12.5 kHz channel

Last edited by blackbird. Register to edit

Tags: none

Packet radio frames include several features to support reliable, addressed data communication. A checksum (or frame check value) is included so the receiver can detect transmission errors: the sender computes a value from the message bytes and sends it along; the receiver computes the same value and compares it to the received value to detect corruption.

If the error check fails, the protocol supports automatic repeat request (ARQ) so the receiver can request retransmission of the corrupt frame. Packet protocols also include a header that carries addressing information (such as the callsign of the destination and often the source) so the packet is routed to the correct station and so stations can identify the sender.

Because packet radio provides addressing, error detection, and retransmission mechanisms, all of these features are included in packet radio transmissions.

Last edited by bud 357. Register to edit

Tags: none

CW stands for "Continuous Wave." Originally the term distinguished an unmodulated carrier that is turned on and off (keyed) from other types of emissions. In amateur radio usage CW is the name given to Morse code transmissions — i.e., Morse code sent by keying a carrier on and off (short and long pulses represent dots and dashes). The historical origin of the name is less important than remembering that CW means Morse code.

Memory aids:

• Take the 'W' in CW and flip it. Now it is an 'M'. Switch the C and M around. Now you have M.C. (morse code).

Last edited by nickatnyt. Register to edit

Tags: none

WSJT is software designed to facilitate short, quick digital transmissions optimized for very weak signals. Because only a small fraction of the transmitted power is received in paths such as Earth–Moon–Earth (moonbounce), weak-signal beacons, and meteor-scatter reflections, the signal-processing and error-correction techniques in WSJT-X make communication possible under those conditions. In other words, WSJT-X supports operation modes used for moonbounce, weak-signal beacons, and meteor scatter.

Memory aids:

• WSJT = Weak Signal JT (JT after Joe Taylor, the program's original author)
• Think “weak-signal” whenever you see WSJT — moonbounce (EME), beacons, and meteor scatter all involve very weak received signals

Last edited by sympathique. Register to edit

Tags: none

ARQ stands for Automatic Repeat reQuest.

Its role is error control: when the receiving station detects that a received block of data is corrupted (for example via a checksum or CRC), it automatically requests the sender to retransmit that block. This provides reliable data delivery over noisy links by allowing corrupted frames to be resent until received correctly. ARQ is not an encryption method, not limited to video, and not a data compression technique.

Memory aids:

• ARQ = Automatic Repeat reQuest
• Think "Repeat Request" = ask sender to resend corrupted data
• Often implemented with ACK/NACK, sequence numbers, and timeouts

Last edited by rprokup. Register to edit

Tags: none

What an amateur radio mesh network is

An amateur radio mesh network is a data network that uses commercial Wi‑Fi equipment (often with modified firmware) to create a many‑to‑many, self‑routing local network. Mesh nodes connect directly and dynamically to other nearby nodes so data can hop from node to node without a central coordinator.

Other items listed in the question are different technologies: digital voice modes such as DMR are voice protocols rather than a general-purpose meshed data network; satellite systems are point‑to‑point or store‑and‑forward links rather than a local Wi‑Fi mesh; and repeater linking is often hierarchical or uses internet linking rather than the decentralized, multi‑path topology that defines a mesh.

Memory aids:

• Mesh = many‑to‑many (not hierarchical)
• Think Wi‑Fi hardware + modified firmware = flexible local mesh routing

Last edited by ferrick_connor. Register to edit

Tags: none