Digital Modes Samples
           
Click on a digital mode below to hear a brief sample of the sound these modes make. Hopefully this page will help you identify a mode you've heard (or help me identify ones others have heard!).  Many folks have submitted excellent quality, lengthy files which are no trouble for me to accept, but I do generally drop the sampling rate and length to make them more reasonable to download over a slower line.  The intent here is more for recognition by ear than for signal analysis. My page focuses on what hams call "Utility" modes or "Utes". Additional amateur radio mode links are at the bottom of the page.
Send me your .wav files of digital modes not featured and I'll happily add it, paying credit where due. High sample rates and large files are encouraged. Please include frequency and user info to help ID your sample. Your comments or clarifications are always welcome. Send mail to garyhahn@wi.rr.com.
Send mail to: garyhahn@wi.rr.com 6/19/2009 Uncompressed files link - good luck
           
Sound Acronym Description Common Freqs Links Special Thanks
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.   More info  
JT65A   Weak signal mode used to make contacts all over the world with 10-15 watts of power. 14075 KHz USB WSJT John KC0BMF, Bob VE2HAR
RTTY 45 baud Radio TeleTYpe Sends text as 5 bit characters with no error correction. 45 baud is the Amateur standard. 14075 KHz USB More info  
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   Unknown
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 More info Van Lanphear
VFT Voice Frequency Telegraphy An older USAF RTTY-like data mode. a.k.a. VFCT - Voice Frequency Carrier Telegraphy HF band   Mike McRoberts
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 More info  
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 More info Pic from Mir on 145.985
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 More info  
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   Scott, Jerry in IL
EMWIN Emergency Managers Weather Information Network 1200bd and 9600bd datastreams. Not sure which one this is. Recording is via microphone, so the hollow tonality is not likely what you'll hear.     Bob W0NXN. Could use a better recording.
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.   Add'l sample from UP Railroad in CA. Steve Donnell, David Curlee
Golay Named after a mathematician Golay is a 300/600 baud paging signal developed by Motorola. Addressing and overhead is 300bd, while data is 600bd. 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.   Gary Gray, Dan Karg
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 More info  
ReFLEX 2-way paging (outbound sample) Reflex 50 on 940.220 Skytel, Reflex 25 on 940.8625 US Mobility. Replies from pagers are on 901-902MHz. 940MHz US. There are 4 10kHz channels embedded at 940.21, .22, .23, .24.   EJ Caylor, Dan Karg, Mike Candell
ERMES European Radio MEssage System 6250 baud paging format used in Europe 169MHz in France, Hungary, Malaysia More info  
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 and 928MHz   Steve D.
BPL Broadband over Power Line As heard on an HF freq. BPL components are scattered about the 1-30MHz band where implemented. (sample from Australia)   Andreas, Borynski
Glenayre Paging Link QAM;Quadrature Amplitude Modulation Links from paging head end to pager transmitter sites. Glenayre C2100/C2000 model control systems are likely in use. As used on what used to be an Ameritech IMTS frequency 152.54   Chuck Huffman, Mike Candell
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   anonymous in CA
MODAT   Used as ANI or status indicator, precedes or follows voice.     Lindsay Blanton
GE-Star   Used as ANI or status indicator, precedes or follows voice. 155.445 WI State Patrol D1   Lindsay Blanton, Jake Guild
MDC1200   Used as ANI or status indicator, precedes or follows voice. 154.130 Milw FD   Jake Guild
MDC1800   Used as ANI or status indicator, precedes or follows voice. Heard here with preamble and post-transmission ID   Kevin H
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   Jon in Australia
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 More info Mike Mannchen
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.     Charles Guerin, Eric Hoefert
Gandalf Mobile Dispatch   Licensed to American United Cab in Milwaukee area, evidence of MDT usage. 152.42 in Milwaukee, WI   Sean Douglas, anonymous
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 More info Bob Brown
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? More Info Barry W, Jim Korth
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. More info Dave Huoy
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 More info 1200/1800Hz Mark/Space
ARES Railroad Telemetry   Used by the BNSF railroad. Data transmission protocol is same as ACARS, datagrams same as ATCS. 2400bd 161.325, 160.365 Northern IL More info Dave Huoy
Harmon MCS-1/2 base   As used on the CP railroad in WI on the 952MHz band, base side for signal and track control. 300bd 952.28125 in Jefferson Co, WI   Erik Coleman
Harmon MCS-1/2 wayside   As used on the CP railroad in WI on the 928MHz band, wayside for signal and track indication. 300bd 928.28125 in Jefferson Co, WI 1186 Mark, 970 space, 300 baud, 8, E, 1. Erik Coleman
Mobile Data Systems MDS9710 - RR Base Encoded with Harmon HP-1 As used on the CN railroad on the ex-IC Dubuque Sub on the 941MHz band, base side for signal and track control. 9600bd 932.34375 at Freeport, IL    
Mobile Data Systems MDS9710 - RR Wayside Encoded with Harmon HP-1 As used on the CN railroad on the ex-IC Dubuque Sub on the 932MHz band, base side for signal and track control. 9600bd 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. 150bd 952.13125 on the UP at Ellis, IL   Doug Nipper (sample) Anonymous (ID)
Union Switch & Signal 550 Flexicode wayside   As used on the UP railroad on the 928MHz band, wayside for signal and track indication. 50 bd 928.13125 on the UP at Ellis, IL   Doug Nipper (sample) Anonymous (ID)
Harmon HP-1 Railroad Codeline Base 201C 2400bd 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   Doug Nipper
Harmon HP-1 Railroad Codeline Wayside 201C 2400bd 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   Doug Nipper
Meteor BNSF RR HLCS(HyRail Limits Compliance System) and ETMS (Electronic Train Management System) As used on the BNSF railroad nearly system-wide for vehicle location reporting, detectors, and other statuses. Also used for the West Texas MesoNet weather sensors on 44.48MHz FM. 9600bd 44.58 FM (recording is from open-squelch USB and compressed)   KC9DRX
FEC RR Telemetry unknown protocol As used by Florida East Coast railroad for signal and track control. Said to sound like Motorola Intrac. 600bd. 160.455 and 161.190 FM    
SEAR   Used by various US railroads for grade crossing status reporting. 1200bd protocol. Some packets demodulate to ASCII printable messages. US AAR railroad VHF band    
LLWAS Windshear telemetry Low Level Windshear Alert System As used at the Madison airport for a type of weather conditions monitoring system.  6 bursts from different transmitters, with about a 20 second pause between cycles. 162.275 in Madison, WI Description Chris Carter
Mobitex   As used in US by RAM mobile data. 935-940 MHz band US   anonymous from UK
CDPD Cellular Digital Packet Data Typically uses vacant cellular voice channels to transmit 19200 baud data.     Steve Donnell
Paknet   This is another British commercial data system. It uses an X.25 access system. 164 MHz UK   anonymous from 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   Alex Skafidas, John Kristian Snekvik, anonymous
LoJack downlink   Not sure what protocol this is, but it is used to direction find stolen vehicles and/or disable ignition. 1200bd, Binary 0 = 1.5 cycles @ 1800Hz, Binary 1 = 1 cycle @ 1200Hz 173.075 nationwide US    
Cognito   This is another British commercial data system 178 MHz UK   anonymous from UK
IMTS idle tone Improved Mobile Telephone System Heard from a distance, a constant tone. Last system in North America decommissioned in 2002. IMTS was the predecessor to the modern cell phone. VHF and UHF allocation in the US More info Robert Johnson
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? More info  
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 More info  
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 More info  
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 More info  
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 More info  
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 P25 makes it industry standards compliant for smooth interaction with neighboring systems. 851-869 MHz band US, others More info  
Motorola IMBE (ASTRO APCO-P25 Trunked) Digital Voice Improved Multi-Band Excitation - Project 25 This is to be the Common Air Interface (CAI) specified by the APCO Project 25 or P25 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.   More info  
Motorola IMBE APCO P25 (non-trunked) Digital Voice   Another variation of the CAI, like in trunked systems, but apparently the pre/post-amble is handled a bit differently.     Todd Hartzel
MOTOTRBO AMBE++ ETSI-TS 102 361-1, -2, -3 Motorola's foray into digital voice for the commercial market?   More info Terry Green
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 More info  
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 More info  
ProVoice (EDACS)   Digital voice format incorporated into EDACS trunked systems.     Warren Whitby, Peter Laws
Aegis Digital Voice (Ericsson)   Digital voice format incorporated into EDACS trunked systems.   More info Charles Guerin
VSLEP Digital Voice   Digital voice format as used by Motorola radios prior to IMBE format.     Rich Carlson
OTAR Over The Air Re-key Transmitted to DES capable radios to update encryption key. 160MHz Fed Band US   Lindsay Blanton
DES Encryption Digital Encryption System? Probably the most common encrypted digital voice format. Commonly heard on same freqs as analog voice. Most prominent feature is the high pitch end of transmission tone. 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   Mike Hein, others
Racal Cougar Voice Encryption   Voice Encryption used by military and special law enforement units. Mostly UK.   Bob
Voice Inversion Scrambling   Simple voice inversion scrambling. Not digital, per se, but interesting.   F1 Scanner Group Bob
TETRA Control Channel Trans-European Trunked RAdio Digital trunked radio, primarily European 390.2375 NFM in Spain; TETRA Emergency Services
380-383 MHz and 390-393 MHz
383-385 MHz and 393-395 MHz (if required)

TETRA Civil Systems
410-430 MHz
870-876 MHz / 915-921 MHz
450-470 MHz
385-390 MHz / 395-400 MHz
  Miquel in Spain, Rickey Stein, Charles Guerin, and anonymous. Need TETRA voice sample
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   Bruce in Colorado
M/A-Com - OpenSky   Voice is a 2 slot TDMA AMBE CODEC from DVSI. Recorded from the PA state system. FedEx uses OpenSky nationwide - in Chicago it's on 860.8625 and other freqs. 851-869 MHz band Pennsylvania state system More info Ben Russell
M/A-Com - P25/IP control channel   M/A-COM's P25 trunked radio system control channel. Sounds different from Motorola's breed, but apparently P25 scanners can track the control channel. as recorded from the 2008 democratic convention temporary system in Denver, CO More info thanks, anonymous!
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.   More info Isidoro Hernandez, Carolina, Puerto Rico. Also Matthew Sadler.
Midland CMS Trunking Control   In Jasper, IN area, also in Ottawa, Ont. David confirmed the type. 857.0875Mhz in Jasper, IN   Chris in IN, David Harris in Ont
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 More info anonymous from UK
MPT1317   A data format found in the UK. It is a variant of MPT1327. Said to be 1200bd MPT1327 in time share mode with other sites on same freq. 86.5875 MHz UK   anonymous from UK, Adam Willis
Motorola iDen (Nextel)   A digital modulation scheme used by the Nextel digital cellular system. 851-869 MHz band US More info  
Kenwood Nexedge Kenwood Nexedge A trunking system control channel proprietary to Kenwood. (Supports the NXDN digital voice mode.) Sounds similar to Motorola Type 2 control channel. NFM modulated bands More info anonymous from Wisconsin.
Kenwood NXDN Kenwood NXDN A digital voice modulation proprietary to Kenwood. 6.25kHz wide using DVSI AMBE++ vocoder. NFM modulated bands Analog/digital comparison using NXDN Rich Dunajewski, by David Sterrett, N1DAS
Rolling Code Inversion   Voice scrambling. Possibly called "Midian". Radios by Transcrypt International? Data burst at the start is the scrambling sync required to descramble. 410-420Mhz in Quebec.   Thierry Juan, anonymous
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 More info  
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   anonymous local
110bd ASCII Utility Telemetry   Similar in use to the power/water utility stuff above, on the same freq. This one from Ridgeland, MS water system. 154.45635, 154.46375, 154.47135, 154.47885 US allocations Decodes in 110bd ASCII inverted as: WL8B14ETH*- <brk> WL8B14ETH*- <brk> !00512700000018WL7CTH*- <brk> WL8B14ETH*- <brk>
!00512700000018WL7CTH*- <brk> !D00B37007E00000099TH7B- <brk> !B701TJ99- <brk> !7A03TK9B-B
<brk> !F003TL9A- <brk> !D203TQ9F <brk> TR02038TS ...etc....
Brian Williams, Matt in France
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 More info  
Zetron Model 6/26   1200 baud FSK telemetry for fire station alerting. 154.175 Waukesha, WI More info Frank Monaco
Radionics Safecom   Alarm system telemetry. ?   Jon in Australia
LaCrosse Technology Weather Sensor FSK Used by consumer remote weather sensors to indoor displays. 433.92MHz from a RR3-433 hybrid board.   "Bit Four" requests additional protocol info
Tone Controlled Remote Base Station   Signals a transmitter to unkey. Audible residue of wired direct connection to repeater/transmitter site. (listen to the end of this sample to hear it)   Dan Morley, thanks to Mike I for info, John Bacon
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 More Info  
TAG CTX330 F1 Telemetry   Formula 1 Grand Prix car to pit   F1 Scanner Group Bob
Magneti Marelli F1 Telemetry   Formula 1 Grand Prix car to pit   F1 Scanner Group Bob
Magneti Marelli F1 Telemetry   Formula 1 Grand Prix car to pit   F1 Scanner Group Bob
Magneti Marelli F1 Telemetry   Formula 1 Grand Prix car to pit   F1 Scanner Group Bob
Pi Research Pi96 Fq Telemetry   Formula 1 Grand Prix car to pit   F1 Scanner Group Bob
Pi Research Pi96 Fq Telemetry   Formula 1 Grand Prix car to pit   F1 Scanner Group Bob
Pi Research Pi96 Fq Telemetry   Formula 1 Grand Prix car to pit   F1 Scanner Group Bob
TAG CTX400 F1 Telemetry   Formula 1 Grand Prix car to pit   F1 Scanner Group Bob
TAG CTX400 F1 Telemetry   Formula 1 Grand Prix car to pit   F1 Scanner Group Bob
Magneti Marelli Step 9 ECU Engine Control Unit Formula 1 Grand Prix car to pit 400.825 in Canada   Charles in Montreal, Bob
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Mysteries!   Heard from home or as noted.      
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Mystery MDT   Denmark national rescue service As used in Denmark   Martin in Denmark
Mystery USAF     As heard on 294.8MHz normally used by USAF for air refueling over Europe.   Tigger in UK
Mystery     As used by West Midlands Fire Service (UK)   Paul in Birmingham
Mystery Yellow Cab     As heard in Memphis, TN 152.3MHz in 2004   Adam Myrow
Mystery Inmarsat Digi   Inmarsat is a commercial satellite phone provider primarily created for ship use. This was heard on one of the channels in 2004, very continuous. AOR-East 1537.8690 MHz USB   Barney Hamlin
Mystery Telemetry     866.0625 in Montreal   Patrice Coulombe
Mystery HF 3606 kHz sounds like MIL STD 188-141 ALE   3605.82 kHz   Justin KJ4EPQ , Matt from France
Mystery HF 3644 kHz sounds like LINK-11 As heard from NW Ohio. .     Mike WW8MM, Matt from France
Mystery HF 3831 kHz sounds like LINK-11 As heard from France.     Bob Brown, Matt from France
Mystery Railroad Codeline   As formerly used on the P&L RR in Kentucy for signal and track control. 4800bd 160.455 on the P&L   Chris Dees
Mystery 864.0875 - Probably MPT13?7   As used on an LTR trunked system in Milwaukee, probably an MDT of sorts.      
Mystery Telemetry   Possibly siren activation telemetry in Suffolk Co, NY. Possibly 46.46 MHz   David Morgan
Mystery Telemetry   Probably utility telemetry/SCADA on a 6.25kHz offset channel near 941.275 in NE TX.     Grady Whitney
Mystery 466.175 Australia   Used by United Water International Pty in Adelaide, Australia with emissions desi 16K0F1D. 466.175 AU License Mark Jessop
Mystery 154.46375   Power/water utility telemetry, at least in Northern IL, is used to control "power line caps (capacitors)" which compensate for load varitions in the power grid. 154.45635, 154.46375, 154.47135, 154.47885 US allocations   anonymous in IL, please remind me what the "name" of the protocol or mode is.
Mystery 467.9    Data from survey equipment as used by Edgerton Contractors levelling a grade, hand-held style radio visible attached to portable unit      
Mystery QuickSilver   QuickSilver Couriers MDTs on 864.7375 and others on an LTR trunked system in Milwaukee.      
Mystery MCTS   Milwaukee County Transit System uses this data for AVL fixes and misc MDT stuff.      
Mystery VSELP?   Pretty sure this is VSELP (Vector Sum Excited Linear Prediction) digital voice.  Used in conventional mode on a MI gas utility on 451.075 and reported as used by the Secret Service in PA.     Michael in PA
Mystery MDT   Licensed and confirmed to Wisconsin Gas in Milwaukee area, evidence of MDT usage.      
Mystery RD-LAP?   Licensed to MI Gas in Grand Rapids area. Sounds like RD-LAP at an odd bit rate.      
Mystery MDT   Licensed to John Aegerter in Milwaukee area, evidence of MDT usage, possibly Butler, WI PD. Possibly Cerulean brand Packet-Cluster MDT service, maybe transported by a DataRadio RF modem. 152.69 in Milwaukee, WI, others More info Bob Brown
Mystery MDT   Believed to be a Motorola MDT format. 453.1 in Hidalgo Co, TX   T. in TX
Mystery   Telemetry? In Jasper, IN area.     Chris in IN
Mystery digital voice   Formula 1 Grand Prix car to pit 414.175 in Canada   Charles in Montreal
Mystery telem/voice   Formula 1 Grand Prix car to pit, possibly scrambled, possible interspersed telemetry 457.275 in Canada   Charles in Montreal
Mystery telemetry   Possible survey data from local municipality. 452.825 in Milwaukee, WI    
Mystery status box   As used by a cement truck firm. 452.25 in Milwaukee, WI    
Ontario Provincial Police Trunking VHF Modat trunking based on MDC1200 As heard in Canada. Marker channel. System phasing out in favor of ASTRO trunked. 141.450 in Canada recording in AM? Paulo Lima in Canada, David Harris
Mystery telemetry   BC Forest Service weather telemetry 402.0375 in Salmo, BC   Neil Walker in BC
Mystery Utility telemetry   Utilicorp Canada 155.325 in Trail, BC   Neil Walker in BC
Mystery telemetry   Teck-Cominco 457.0125 in Trail, BC   Neil Walker in BC
Mystery MDT   Used by police in Netherlands     Huub Roem
Mystery   Possible hospital paging, sent every minute 29.9 NFM in Norway   John Kristian Snekvik
Mystery   Possible security company freq 142.425 NFM in Norway   John Kristian Snekvik
Mystery (ISS?)   Possible xmission from International Space Station's Russian Zvezda module 143.625 NFM in Norway   John Kristian Snekvik
Mystery telemetry   Possible power plant telem (Trondheim?) 166.250 NFM in Norway   John Kristian Snekvik
Mystery Trunked Radio System   Norwegian Railways - Possible trunked system? 467.700 NFM in Norway   John Kristian Snekvik, Martin Kristiansen
Mystery Skytrain   Skytrain in Vancouver uses this 410.7875 possibly MPT13?7, sync only Jason in Vancouver, Matt from France
Mystery Skytrain   Skytrain in Vancouver uses this 410.9375 possibly MPT13?7 Jason in Vancouver, Matt from France
Mystery   Possible trunked system 834.025 NFM in Norway   John Kristian Snekvik
Mystery   Military in Netherlands? 455 MHz band in Netherlands   Hans
Mystery   Something in Canada? 424.3125 heard from Niagara Falls area   Mike Trank
Mystery Fire Dispatch   Used over an EDACS trunked talkgroup for FD station dispatch data. Sounds like AX.25 but does not decode. Hartford, CT EDACS system   Chris Gordon
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Links!   Yep, other folks are warped enough to do this too!
Amateur Radio Modes   WB8NUT      
Amateur Radio Modes   G4UCJ      
MT Utility World   Brought to you Monitoring Times      
UXDF Requires membership. A Yahoo group dedicated to Utility stations monitoring. With digi modes sound files.      
Class C Telemetry Requires membership. A Yahoo group dedicated to CB band gadgets. With digi modes sound files.