Field guide
What is that sound?
Plain-English plates for 78 kinds of radio signal: what each one sounds like, who sends it, where to hear it, and what it's easily confused with.
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Morse, teletype and text
Plate 07ContestiaLike Olivia: many tones hopping, a little…
Plate 13DominoEXA gentle, flowing sequence of tones, like a slow ripple of…
Plate 17FSK HellA buzzy, rhythmic rasp with a two-tone…Plate 18FSQ (Fast Simple QSO)A soft, stepping sequence of…
Plate 24Hellschreiber (Feld Hell)A rough, rasping buzz with a steady…
Plate 26IFKPA gentle, stepping sequence of…
Plate 35MFSK (MFSK16/32)A rapid, bubbling series of pure…
Plate 36Morse code (CW)A clean, steady beep turning on and off in a rhythm, like a very fast…
Plate 38MT63A dense, steady rushing sound, like wind with a musical…
Plate 40NAVTEX (maritime safety text)A rhythmic, chirpy two-tone chatter at a steady…
Plate 43OliviaA choir of tones hopping up and down, like a slow, busy music…
Plate 51PSK31A soft, steady warbling tone, often several side by…
Plate 52PSK63 / PSK125Like PSK31 but a slightly rougher, faster…
Plate 54Radioteletype (RTTY)A fast, two-note warble or 'diddle', like a rapid bird…
Plate 56SCAMPA plain two-tone or on-off keying pattern, slower than…
Plate 67ThorSimilar to DominoEX: flowing, stepping…
Plate 68ThrobA slow, pulsing, throbbing…Weak-signal digital (FT8 and friends)
Plate 19FST4 / FST4WSlow, faint tones over long turns, similar to…Plate 20FT2Short, warbling bursts like FT4, but quicker, repeating every few…
Plate 21FT4Like FT8 but slightly wider and rougher, with turns switching every 7.5…
Plate 22FT8Many soft, quiet musical warbles side by side, starting and stopping together…
Plate 28JS8CallLike FT8: soft warbling tones in timed…
Plate 29JT4Slow, steady tones over nearly a…
Plate 30JT65A slow, burbling series of tones lasting most of a minute, starting at the top…Plate 31JTTYA steady four-tone warble, similar to FT4 but without the regular on-off rhythm…
Plate 37MSK144 (meteor scatter)Mostly silence with sudden short 'pings' when a meteor trail reflects the…
Plate 79WSPR (propagation beacons)A faint, very slow, steady tone that shifts pitch slightly, lasting almost two…Pictures
Voice
Plate 04AM voiceNormal-sounding speech or music, often with background hiss and fading on…Plate 08D-STAR digital voiceA smooth, hissy digital…Plate 09Digital Radio Mondiale (DRM)A flat, steady block of hiss about 10 kHz wide, with no…Plate 12DMR digital voiceA raspy, buzzing sound with a pulsing edge, like angry…Plate 15FM broadcastHigh-quality music or speech, often…Plate 16FreeDV digital voiceA steady rushing hiss about as wide as a voice signal, with no speech you can…
Plate 33M17 digital voiceA buzzing digital sound similar to other digital voice…
Plate 39Narrow FM voiceClear, quiet speech that cuts in and out as people press and release the talk…Plate 42NXDN digital voiceA tight, buzzing digital…Plate 45P25 digital voiceA steady, gravelly digital…Plate 58Single-sideband voice (SSB)Clear speech when tuned exactly; slightly off-tune it sounds high-pitched or…Plate 65System Fusion (C4FM) digital voiceA harsh, buzzing digital…Plate 66TETRAA continuous, dense digital…
Plate 33M17 digital voiceA buzzing digital sound similar to other digital voice…Plate 39Narrow FM voiceClear, quiet speech that cuts in and out as people press and release the talk…Plate 42NXDN digital voiceA tight, buzzing digital…Plate 45P25 digital voiceA steady, gravelly digital…Plate 58Single-sideband voice (SSB)Clear speech when tuned exactly; slightly off-tune it sounds high-pitched or…Plate 65System Fusion (C4FM) digital voiceA harsh, buzzing digital…Plate 66TETRAA continuous, dense digital…Aircraft, ships and utility
Plate 01ACARS (aircraft messages)A short, shrill burst, like a squeaky modem, heard in…Plate 02AIS (ship positions)Short, harsh data…Plate 03ALE (automatic link establishment)A brief, chirpy, bubbling warble, from about a second to several seconds long,…Plate 10Digital Selective Calling (DSC)A brief, fast two-tone warble lasting a few…Plate 25HFDL (aircraft data over shortwave)Short bursts of dense digital noise, plus regular 'squitter' announcements from…
Plate 47PACTORShort chirping bursts that alternate between two stations, back and…
Plate 61STANAG 4285 (NATO modem)A steady, rough hiss about 3 kHz wide, like a waterfall of…Plate 74VDL Mode 2 (aircraft data link)A short, dense burst of digital…
Plate 47PACTORShort chirping bursts that alternate between two stations, back and…Plate 61STANAG 4285 (NATO modem)A steady, rough hiss about 3 kHz wide, like a waterfall of…Plate 74VDL Mode 2 (aircraft data link)A short, dense burst of digital…Packet, paging and tones
Plate 05APRS (position and messaging)A short 'brrrap' data burst every so often, like an old…Plate 11Digital squelch code (DCS)Usually inaudible; sometimes a faint low…Plate 34MDC-1200 radio ID burstA quick 'brrrp' at the beginning or end of someone…
Plate 46Packet radio (AX.25)A short, harsh 'brrrap' buzz, like an old dial-up…Plate 48Pager signal (FLEX)A continuous, rough digital buzz or…
Plate 49Pager signal (POCSAG)A harsh, buzzing 'brrrrt' burst, like a fast fax or…Plate 57Selective calling tonesA quick run of musical notes, like…Plate 63Sub-audible tone (CTCSS / PL)Usually filtered out, so you often can't hear it at all; sometimes a faint low…
Plate 70Touch-tone (DTMF)Short beeps that sound exactly like pressing phone…Plate 71Trunked-radio control channelA constant, never-ending digital buzz or…Satellites, radar and time
Plate 41Numbers stationA synthetic or recorded voice reading numbers, sometimes with a tune or tone…Plate 44Over-the-horizon radarA rapid, harsh tapping or 'woodpecker' sound, or a fast sweeping…
Plate 53Radar pulses and soundersA quick 'zip' or chirp as a sweep passes by, or regular clicks and…
Plate 55Satellite telemetry beaconShort data bursts (like packet radio's buzz) or a steady tone, sliding in pitch…Plate 69Time signal stationRegular clock-like ticks, one per second, with a voice announcing the time each…
Plate 76Weather satellite pictures (APT)A distinctive 'tick-tock' sound, two ticks per second (APT ended in…
Plate 53Radar pulses and soundersA quick 'zip' or chirp as a sweep passes by, or regular clicks and…Plate 55Satellite telemetry beaconShort data bursts (like packet radio's buzz) or a steady tone, sliding in pitch…Plate 69Time signal stationRegular clock-like ticks, one per second, with a voice announcing the time each…Plate 76Weather satellite pictures (APT)A distinctive 'tick-tock' sound, two ticks per second (APT ended in…Sensors (433 / 868 / 915 MHz)
Interference and noise
Plate 06Broadband internet or powerline network noiseA steady, hissing roar, like rushing water, over whole sections of the…Plate 14Electric fence ticksA sharp tick or pop about once a second, like a slow…Plate 27Interference or noiseBuzzing, hissing, crackling, whining or…Plate 50Power-line noiseA harsh, raspy buzz, often with a 120-times-a-second rhythm (100 in 50 Hz…Plate 60Solar inverter or motor-drive noiseA buzz, whine or rough 'comb' of tones that comes and goes with the…Plate 62Steady carrierOne constant whistle or tone that doesn't…Plate 64Switching power supply / LED noiseA whine, buzz or rough carrier that may drift, repeating every few tens of…Plate 72TV or display buzzA buzzy hash with a steady low rhythm, starting and stopping when the screen is…
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Also see Mystery and famous signals.