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Digital Modes and Sounds Heard On The Airways

Mode and Sound

Acronym

Description

Frequency

CW 20 wpm Continuous Wave Continous Wave is technically a modulation scheme, but the term CW is often used interchangeably with Morse Code. This sample is keyed at 20 words per minute. Many repeaters ID in Morse Code.   
RTTY 45 baud Radio TeleTYpe Sends text as 5 bit characters with no error correction. 45 baud is the Amateur standard. 14075 KHz USB
RTTY 75 baud Radio TeleTYpe Same as above, except faster. Commonly used in weather data transfer. 10536 kHz USB
SITOR-A Simplex Telex Over Radio Sends data in a two frequency mode, one for sending and one for receiving an acknowledge. The brief pause you hear in this sample is where the receiving station sends the acknowledge burst.  Automatic Repeat reQuest guarantees delivery.  
AMTOR ARQ Amateur Teletype Over Radio As above.  
SITOR-B Simplex Telex Over Radio In this case using Forward Error Correction mode, minimizing errors. Identical format used in SITOR - SImplex Teletype Over Radio, and NAVTEX - NAVigational TEleX.  14070, 6330, 518 kHz, respectively
AMTOR FEC Amateur Teletype Over Radio As above.  
ROU-FEC 164.5/218.3 bd Roumanian FEC See above for FEC explanation. HF band
SWED-ARQ Swedish ARQ As above. HF band
PSK-31 Phase Shift Keyed Currently, a quite popular amateur mode providing highly readable teletext over great distances on low power on narrow bandwidth. HF band
MFSK Multi-Frequency Shift Keying Sequential multi-tone data mode near 64bps. HF band
VFT Voice Frequency Telegraphy An older USAF RTTY-like data mode HF band
Hyperfix   A military data or sounding mode. HF band
Hyperfix   As above. HF band
ALE Automatic Link Establishment Propagation sounding and messaging used by the military. HF band
SSTV Slow Scan TeleVision Amateur video mode carries images one scan line at a time by using a frequency shift for each pixel. 14230 kHz USB
WeFax Weather Fax Used to send weather maps and photos primarily to ships at sea and operates similarly to SSTV 8080 kHz USB
Packet 300 baud   Amateur Packet radio sends data in bursts at 300 baud, and waits for an acknowledge packet from the other end before sending the next packet. 14105 kHz USB
Packet 1200 baud   As above, but faster. 144.39 NFM, 145.030 NFM
Bell 103 modem 300 baud   Used by WB9AGH weather wire in a Chicago suburb for transmission of weather info.  Can be decoded with a telephone modem. 147.060 NFM
Pactor   A sort of combination of Packet and AMTOR used by ships and Amateur Radio on HF. HF band
5/6 tone paging   Used for simple tone or voice pagers or ANI.  This sample has 2 sequences reading 0-123456 when decoded, the first set use an optional preamble.  
Golay Named after a mathematician Golay is a 600 baud paging signal developed by Motorola. Also, Motorola DPL uses the same protocol format as a subaudible tone set of a 23 bit repeated word sent at a 134.5 Hz rate.  
POCSAG 512 baud Post Office Code Standarisation Advisory Group A paging format originating in the UK, used widely in the US. 152, 454, 929, and 931 MHz US
POCSAG 1200 baud   As above, only faster.  
POCSAG 2400 baud   As above, faster yet.  
FLEX   Another paging format common in the US.  2 or 4 level signalling as 1600, 3200, or 6400bd rates. 929 and 931 MHz US
ERMES European Radio MEssage System 6250 baud paging format used in Europe 169MHz in France, Hungary, Malaysia
AFSK Paging Link Audio Frequency Shift Keyed At the paging Tx site, this AFSK is decoded into the "digital" FSK format (e.g, POCSAG). 72-75 MHz US, also old mobile phone freqs
FLEX Paging Link?   Pretty sure this is a paging link from terminal to transmitter 940MHz US
Speedcall DTMF Dual Tone Multi Frequency Yep, just like telephone dial, but quite rapid.  This particular use is for water utility telemetry.  Also used for other signalling and over the air device activation. About anywhere, as DTMF falls in the passband of most transceivers
MODAT   Used as ANI or status indicator, precedes or follows voice.  
GE-Star   Used as ANI or status indicator, precedes or follows voice. 155.445 WI State Patrol D1
MDC1200   Used as ANI or status indicator, precedes or follows voice. 154.130 Milw FD
MDC4800   Mobile Data Terminals (MDTs) used in Police squads. 858.2625, 855.7375 in Milwaukee, WI
MDC4800 (ARDIS )   Slightly different in sound, Ardis, now Motient, is a packet switched data network for two-way data transfer. formerly 854.8375 in Milwaukee
MDC4800 (ARDIS at 855.8375)   Somewhat different yet in sound. 855.8375 in Milwaukee
MDC4800?   SAPOL - South Australian Police 868.7625 MHz 
RD-LAP 9600 baud Radio Data - Link Access Protocol ? As used by a power utility in Wisconsin. Not fully verified, note similarity to 19.2k variety. 938.9375 in WI by WEPCo
RD-LAP 19200 baud Radio Data - Link Access Protocol ? Mobile Data Terminals (MDTs) used in Police squads. 856.7375, 857.2625 in Milwaukee, also ARDIS now 854.8375
DataRadioIP   Mobile Data Terminals (MDTs) used in Police squads. Uses IP as addressing system and allows Voice Over IP 857.2625 Sheboygan Co, WI
MMP-4800 (MDI)   Mobile Data Terminals (MDTs) used in Police squads and FedEx. Created by a company called Mobile Data International, which was purchased by Motorola.  
Gandalf Mobile Dispatch   Licensed to American United Cab in Milwaukee area, evidence of MDT usage. 152.42 in Milwaukee, WI
DDS 4800bd QPSK Digital Dispatch Systems Licensed to Yellow Cab in Milwaukee area, evidence of MDT usage, credit, GPS. 152.33 in Milwaukee, but any NFM poss
IP MobileNet   19.2kbps MDT system. TDMA voice capable using INVADR (formerly Electrocom) ( likely 4-level FSK with FEC, native IP communications) 139.375 by the WI State Patrol, 852.6125 Rock Co, WI?
ATCS Spec200 Automatic Train Control System 4800 baud data system somewhat similar to MDC4800. US Nationwide license to American Ass'n of Railroads (AAR) Standard 6 base and 6 mobile freqs allocated nationwide US in 935-940 band.
EOTD End of Train Device Used to monitor and control air pressure, etc on US trains.  AAR standard 1200bd FSK protocol. 457.9375, 452.9375
ARES Railroad Telemetry   Used by the BNSF railroad. Data transmission protocol is same as ACARS, datagrams same as ATCS.  161.325, 160.365 Northern IL
Harmon MCS-1/2 base   As used on the CP railroad in WI on the 952MHz band, base side  for signal and track control 952.28125 in Jefferson Co, WI
Harmon MCS-1/2 wayside   As used on the CP railroad in WI on the 928MHz band, wayside for signal and track indication 928.28125 in Jefferson Co, WI
Mobile Data Systems MDS9710 - RR Base   As used on the CN railroad on the ex-IC Dubuque Sub on the 941MHz band, base side  for signal and track control 932.34375 at Freeport, IL
Mobile Data Systems MDS9710 - RR Wayside   As used on the CN railroad on the ex-IC Dubuque Sub on the 932MHz band, base side  for signal and track control 941.34375 at Freeport, IL
Union Switch & Signal 550 Flexicode base   As used on the UP railroad on the 952MHz band, wayside for signal and track control 952.13125 on the UP at Ellis, IL
Union Switch & Signal 550 Flexicode wayside   As used on the UP railroad on the 928MHz band, wayside for signal and track indication 928.13125 on the UP at Ellis, IL
Harmon HP-1 Railroad Codeline Base   As used on the CN/IC railroad on the 952MHz band, wayside for signal and track control 952.18125 on CN/IC at Tolono, IL
Harmon HP-1 Railroad Codeline Wayside   As used on the CN/IC railroad on the 928MHz band, wayside for signal and track control 928.18125 on CN/IC at Tolono, IL
Mobitex    As used in US by RAM mobile data. 935-940 MHz band US
CDPD Cellular Digital Packet Data Typically uses vacant cellular voice channels to transmit 19200 baud data. FedEx apparently uses a dedicated frequency system in Chicago on 860.8625 and other freqs.  
Paknet   This is another British commercial data system. It uses an X.25 access system. 164 MHz UK
NMT-450 Nordic Mobile Telephones control channel It is a very primitive network (first generation) and uses analog FM with 25 KHz spacing. Similar is NMT-900. 463-470 in Sweden
LoJack   Not sure what protocol this is, but it is used to direction find stolen vehicles and/or disable ignition. 173.075 nationwide US
Cognito    This is another British commercial data system 178 MHz UK
GSM digital cellular Global System for Mobile This form of digital voice transmission is very common in North America, Europe, and the Middle East 890-915 MHz EU?
D-AMPS Cellular voice Digital-Advanced Mobile Phone Service The TDMA based digital standard for the legacy 800MHz cellular system in the US, allowing for 3 conversations per 30kHz channel. 879-881 MHz US
AMPS Cellular Control Channel Advanced Mobile Phone Service This channel tells cell phones what channel to use for voice, and other information. 879-881 MHz US
Motorola Type 1 (old) Trunking Control Channel   This 3600 baud channel is used to tell mobile radios which voice frequency to use. 851-869 MHz band US, others
Motorola Type 1 (newer) or  Type 2 Trunking Control Channel   As above, but the sound here is nearly the same for newer Type 1, and all flavors of Type 2, except networked systems. 851-869 MHz band US, others
Motorola Networked Trunking Control Channel   As above, Networked, or "Smartzone" systems use Type 2 style IDs, which can span across many distinct transmitter sites over a wide area. 851-869 MHz band US, others
Motorola ASTRO APCO-25 Trunking Control Channel   This 9600 baud channel is used to tell mobile radios which voice frequency to use. ASTRO is a digital/analog voice trunked radio system.  APCO-25 makes it industry standards compliant for smooth interaction with neighboring systems. 851-869 MHz band US, others
Motorola IMBE (ASTRO APCO-25 Trunked) Digital Voice Improved Multi-Band Excitation This is to be the Common Air Interface (CAI) specified by the APCO-25 standard.  State of MI State Police, also on a 400 MHz military TRS.  The military system is not using a 9600bd control channel, but seems to be using the same voice format.  
EDACS (Ericsson) Trunking Control Channel   This 9600 baud channel is used to tell mobile radios which voice frequency to use. 851-869 MHz band US, others
EDACS (Ericsson) Narrowband Trunking Control Channel   This 4800 baud channel is used to tell mobile radios which voice frequency to use. NIPSCO, the northern Indiana power utility has a multi-site networked system. 935-940 MHz band US
Aegis Digital Voice (Ericsson)   Digital voice format incorporated into EDACS trunked systems.  
VSLEP Digital Voice   Digital voice format as used by Motorola radios prior to IMBE format.  
OTAR Over The Air Re-key Transmitted to DES capable radios to update encryption key. 160MHz Fed Band US
DES Encryption Digital Encryption System? Probably the most common encrypted digital voice format.  Commonly heard on same freqs as analog voice. 160MHz Fed Band US, various PDs
DES Encryption - Trunked   Same as DES, but on a Motorola trunked system. Note lack of high pitch at end of transmission Motorola TRS
KY57/58 Encryption   Military Voice encryption standard, heard on aircraft/base comms here UHF air band 376.1 AM
Racal Cougar Voice Encryption   Voice Encryption used by military and special law enforement units. Mostly UK.
Voice Inversion Scrambling   Simple voice inversion scrambling.  Not digital, per se, but interesting.  
TETRA Trans-European Trunked RAdio Digital trunked radio, primarily European 390.2375 NFM in Spain
EFJ LTR Trunking Control subaudible Logic Trunked Radio EF Johnson trunking format. This subaudible tone sequence is used to tell mobile radios which voice frequency to use. You will need a set of HEADPHONES or speakers/amplifier with plenty of bass response to hear anything as these tones are "SUBAUDIBLE". The audible tones you hear is just a telephone ring.  851-869 MHz band US, others
M/A-Com - OpenSky Data Network See CDPD, above Apparently uses private CDPD for data.  Voice is a 2 slot TDMA AMBE CODEC from DVSI and likely sounds different from this. 851-869 MHz band Pennsylvania state system
220 MHz SEA LTR Trunking Control pilot tone Logic Trunked Radio As heard in NFM, but actually uses ACSB (similar to SSB) for voice comms. The pilot tone is transmitted about every 10 seconds.  In Milwaukee, 220.0125 is one frequency, but you may have to tune up or down a bit to hear it.  Sorry for the scratchy copy, I'll work on a better sample. 220-222 MHz ACSB
GE MARC-V Trunking   A trunking system which does not use a control channel.  No longer implemented in the US, some systems linger.  
Midland CMS Trunking Control   In Jasper, IN area, also in Ottawa, Ont.  David confirmed the type. 857.0875Mhz in Jasper, IN
MPT 1327 Trunking Control Channel Ministry of Post and Telecom  This format is very common in European countries, Australia, and South Africa.  Might be commonly referred to as TaitNet. This channel is used to tell mobile radios which voice frequency to use. More info
MPT1317   A data format found in the UK. It is a variant of MPT1327. 86.5875 MHz UK
Motorola iDen (Nextel)   A digital modulation scheme used by the Nextel digital cellular system. 851-869 MHz band US
ACARS Aircraft Communications And Reporting System Used to transmit aircraft waypoint, temperature, performance, and other data between to and from the ground station. 131.55 MHz AM
SCADA telemetry Supervisory Control And Data Acquisition Technically this isn't a mode, but a generic term for a data acquistion means. Some of possible data protocols are SC-1801, Harris 5000/6000/XA-21, Telegyr 8979, TRW-9550, and PERT 26/31. This particular signal is heard in the Milwaukee, Wisconsin area. It is a wide signal spanning 952.250 thru 952.750 MHz with this audio being recorded from the center of 952.500 MHz WFM. I have observed directional 900MHz antennas in use at various utility shacks, so I suppose it could be monitoring or control telemetry from these. 952.50625 MHz WEPCo
SSR Secondary Surveillance Radar used to transmit an aircraft's ID number and altitude to ground controllers. It is otherwise known as a transponder and the transmissions are referred to as "squawks". Aircraft squawk on 1090 MHz when interrogated by ground radar. Listen in SSB or AM mode. 1030, 1090 MHz
DMB Data Marker Buoy US Coast Guard drops these beacons to pinpoint Search And Rescue positions and monitor drift of wreckage.  Continuous tones. This one was set to 242.65 MHz. I'm told ELT's on 121.5 sound the same. 243, 121.5 MHz AM
EAS Emergency Alert System tone sequence which has replaced the old EBS annoying tone. These new tones will be used on commercial and National Weather Service radio stations and carry location-specific emergency messages (SAME). 162.4-162.55 MHz FM, bcast radio
CompuLert FSK-FM Frequency Shift Keying Low speed FSK telemetry to monitor and sound warning sirens.  Milw. Co. Emergency Management uses it for tornado siren telemetry.  Voice is also on this freq. 453.375 Milwaukee, WI
Zetron Model 6/26   1200 baud FSK telemetry for fire station alerting.  154.175 Waukesha, WI
Radionics Safecom   Alarm system telemetry. ?
GPS RTK Global Positioning Satellite Real-Time Kinematics Not sure if this is a standard protocol, but the signal is definitely being transmitted from a GPS survey unit to improve accuracy, as close as 1 cm various
TAG CTX330 F1 Telemetry   Formula 1 Grand Prix car to pit  
Magneti Marelli F1 Telemetry   Formula 1 Grand Prix car to pit  
Magneti Marelli F1 Telemetry   Formula 1 Grand Prix car to pit  
Magneti Marelli F1 Telemetry   Formula 1 Grand Prix car to pit  
Pi Research Pi96 Fq Telemetry   Formula 1 Grand Prix car to pit  
Pi Research Pi96 Fq Telemetry   Formula 1 Grand Prix car to pit  
Pi Research Pi96 Fq Telemetry   Formula 1 Grand Prix car to pit  
TAG CTX400 F1 Telemetry   Formula 1 Grand Prix car to pit  
TAG CTX400 F1 Telemetry   Formula 1 Grand Prix car to pit  
Magneti Marelli Step 9 ECU Engine Control Unit Formula 1 Grand Prix car to pit 400.825 in Canada