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| − | ==Why cant I decode this signal?==
| + | '''NOTICE: The rules about listening to signals not intended for you applies here. The contents of many signals might be considered sensitive by the party sending and the reception of such signals may be illegal in your country. The authors neither condone or encourage such acts''' |
| − | Let's be clear at the outset - there are many digital signals that will '''never''' be decoded. Unlike digital signals in the amateur radio service, there are many that are encrypted to prevent casual viewing. Most are assumed to be military in nature. The challenge is to find signals that '''can''' be decoded, or at least identified.
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| | + | This document is designed to give utility listeners a sampling of the kinds of signals and sounds available on shortwave (HF) radio today along with information on the available equipment needed to understand, analyze or identify these signals. Our primary focus is to present the parameters that define the most commonly heard systems as an aid for utility monitors and not an exhaustive discussion of HF |
| | + | digital signaling theory. |
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| − | ==What are all those strange sounds?==
| + | Digital Utility listening is inherently more difficult than regular shortwave listening. The possibility of decoding the signal received adds another level of complexity. This document is an attempt to describe to hobbyists what digital signals can be received and decoded, in addition to providing the more advanced listener with a little more technical data to identify an otherwise unknown signal. |
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| − | The first task is to properly identify the mode. There are numerous digital modes, and a casual examination of the Utility DXers Forum on Yahoo groups would turn these up. | + | Herein lies the basic problem with digital utility listening - lack of information. Many systems are used by Military or Diplomatic Services and information on the specifics of a particular mode are impossible to find, even from the manufacturer. Many are considered proprietary, but that doesn't mean that a signal can not be identified. With the proper tools a given signal can be identified via the way it sounds (aurally) or how it looks (visually). Most of the more expensive decoders that include some kind of signal analysis can ID a signal by bit-pattern or baud rate. Once a signal is identified there are many decoders that can print the traffic for you; however, keep in mind there may be various kinds of encryption in use with these signals. Encryption types include figure group or letter group messages and even random bit-masking or bit stream encryption, which looks like a continuous stream of random characters. You may often read the term "on-line" and "off-line" used in conjunction with various encryption schemes. Generally, off-line encryption is taken to mean groups of letters or numbers (most usually groups of five), whereas on-line schemes just appear as a continuous stream of random characters. |
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| − | * [[ALE]]. This mode is often used to test the propagation path between 2 stations, and to sometimes pass short messages. The link provides more information on this mode as well as compatible software. Note that this one of the newer modes that hams, as well as non-hams, utilize.
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| − | * Digital Selective Calling (DSC). This [http://www.ndblist.info/index.htm website] has a great deal of information, as well as links to software that can read this mode.
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| − | * FAX (Facsimile) - Most often used for weather charts, and on rare occasions, news items. Happily this is one mode that is easy to both recognize and decode.
| + | Keep in mind that you must be able to find a signal before you can apply the power of the decoder on the signal for identification and possible decoding. Most signals found on the airwaves today are obvious with easily distinguishable sounds, from chirping to two tone FSK to musical multitone MFSK, but as communication technology develops this will most likely change. It is safe to say that the more efficient a modulation/coding method is, the more noise like it must become. It has been said in some digital groups that "Any sufficiently advanced communication is indistinguishable from noise". |
| − | ** [http://www.nws.noaa.gov/om/marine/rfax.pdf NOAA Worldwide FAX Schedule] (PDF)
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| | + | This document covers the following areas. Please click on the desired topic; |
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| − | * HF Datalink ([[HFDL]]), also known as HF ACARS. See the linked article for more information.
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| | + | ; Chapter 1. Receivers and PC Connections |
| | + | *[[A Few Words on Receivers]] |
| | + | *[[Making the Connection to the PC]] |
| | + | *[[Connecting Radios to Soundcards]] |
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| − | * Link11 - See the [[Link-11]] article.
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| | + | ; Chapter 2. How Do I Decode A Signal I Find on HF? |
| | + | *[[Decoders|A Discussion About Decoders]] |
| | + | *[[HF Hardware Decoders]] |
| | + | *[[HF Software Decoders]] |
| | + | *[[Utility Monitoring Central Links]] |
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| − | * SITOR-B - Also known as AMTOR Mode B, FEC or NAVTEX, this mode is often used for maritime weather and warnings from various organizations. This [http://www.ndblist.info/index.htm website] also has a great deal of information on this mode. While not used by the amateur community much anymore (apart from W1AW broadcasts), it still enjoys wide popularity in the maritime community.
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| − | ** [http://www.nws.noaa.gov/om/marine/hfsitor.htm USCG HF Sitor schedules]
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| | + | ; Chapter 3. Modes and Sounds |
| | + | *[[HF Modes List]] |
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| − | * STANAG 4285 - Most often used by the French and NATO forces. See this [http://www.udxf.nl/Some%20Notes%20on%20STANAG%204285.pdf article (PDF)] from the Utility DXers Forum homepage on identifying and decoding this mode. Often the traffic is encrypted, but the IDs are not, making it easy to at least identify the users. Occasionally you will get lucky and catch the stations running test loops (in French: Voyez Le Brick) which identifies the station.
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| − | | + | ; Chapter 4. Articles |
| − | While there are many digital signals that are easy to identify, many are not. There are just as many modes that most people have never heard of. This [http://www.udxf.nl/list%20of%20digital%20systems.pdf article (PDF)] is a list of those modes that have been identified, but there are likely more that have never been identified or classified. It's quite possible that these modes are military in nature. These modes could be encrypted and very difficult, if not outright impossible, to read.
| + | *[[Selected Articles from the WUN Archives]] |
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| − | ==So how can we identify the users of these modes?==
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| − | In some cases, the frequencies used by these modes are well known and widely published (such as HFDL). This is, of course, but one clue in identifying a user. We need another tool to help narrow the field.
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| − | Some older modems and TNCs (for example the Universal M-7000) had the ability to attempt to guess what mode a particular signal was sending (some very expensive
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| − | soundcard decoders also have this ability). Unfortunatly these classifiers can be fooled by a poor signal level or noise - so it's not always the best choice for determining the mode of a signal
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| − | Many digital decoding packages have the ability to display an audio representation of the signal being received. This ability comes by many names; sonogram, waterfall display or audio spectrum display, just to name a few. This [http://www.udxf.nl/Living%20Sonagram.pdf article (PDF)] describes in some detail how to use a sonogram and how to record the signal. Both are important - you may need to play the signal back several times before you get a clear picture of what the signal looks like. The accuracy of the sonogram is going to be greatly influences by many factors; the quality of the signal being received, your receiving setup and the PC you are using will all play a role here.
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| − | It should be noted that new modes show up from time to time that take considerable knowledge and skill to properly analyze.
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| − | Now what about identifying the patterns shown in the sonogram?
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| − | These links have pictures of sonograms (and in some cases audio samples) of numerous kinds of digital signals. You can use these as a guide, but remember, it's another clue as to the mode (and by extension, sometimes the potential user) of the signal
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| − | * [http://www.bartg.org.uk/modesamples.asp British Amateur Radio Teledata Group Mode Samples] | |
| − | * [http://www.w1hkj.com/FldigiHelp-3.21/Modes/index.htm Digital Modes - Sight & Sound]
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| − | * [http://www.bcar.us/digsig.htm Digital Signal Audio Reference]
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| − | * [http://det.bi.ehu.es/~jtpjatae/sound.html Eduardo Jacob's Home Page- Sound Files]
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| − | * [http://www.w1hkj.com/FldigiHelp-3.21/Modes/index.htm fldigi samples of decodeable modes]
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| − | * [http://hfradio.org.uk/html/digital_modes.html G4UCJ's Radio Website]
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| − | * [http://sferix.myweb.hinet.net/hfasia/ HF Asia Sound Files]
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| − | * [http://www.iarums-r1.org/iarums/sound/main.html IARU Monitoring System Region 1 Sound Files]
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| − | * [http://www.jvcomm.de/soundframee.html JVCOMM32 Sound Samples]
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| − | * [http://www.kb9ukd.com/digital/ KB9UKD Digital Modes Samples]
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| − | * [http://www.qsl.net/lu8mbr/digimodos.htm LU8MBR Digimodos (Spanish)]
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| − | * [http://www.mixw.net/index.php?j=signals MixW digital signal examples]
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| − | * [http://f1ult.free.fr/DIGIMODES/MULTIPSK/digimodesF6CTE_en.htm MultiPSK - Digital Mode Samples]
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| − | * [http://www.nonstopsystems.com/radio/radio-sounds.html NonStop Systems Radio Sound Samples]
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| − | * [http://signals.radioscanner.ru/base/ Signals RadioScanner RU Signal Samples] (page partially in Russian)
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| − | * [http://signals-analysis.blogspot.com/ Signals Analysis Blog]
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| − | * [http://www.sigidwiki.com/wiki/Signal_Identification_Guide Signal Identification Guide (wiki)]
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| − | * [https://www.youtube.com/user/FirstToken/videos Token's Audio Samples] includes several digital signals
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| − | * [http://www.udxf.nl/modes.html UDXF Audio Samples]
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| − | * [http://wb8nut.com/digital/ WB8NUT Digital Information Page]
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| − | * [http://www.qsl.net/zl1bpu/ ZL1BPU Fuzzy Modes]
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| − | ==What about decoding?==
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| − | There are numerous packages that can decode many of the non-encrypted modes that you will find on HF. The [http://www.chace-ortiz.org/umc/software.html Utility Monitoring Central] website lists packages for PCs, Macs and even a few for IPADs. Some are free, some not. Msst require a simple connection between your PC and your receiver. Marius Rensen's popular [http://www.hffax.de HF FAX] site has more information on FAX software and schedules
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| − | In the case of connecting a receiver to the PC soundcard, a clean connection is a must. This [[Connecting Radios to Soundcards|article]] from our wiki describes some pitfalls and solutions. It's strongly encouraged to make the connection with shielded audio cable to restrict the possibility of stray noise pickup. However, you will need to experiment with the soundcard settings on the PC to see which works for you. There's no way to present a guide for each and every instance, as there is wide variation in models and quality, depending on the soundcard installed on the PC.
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| − | Connecting a PC soundcard to your Software Defined Radio (SDR) may require the use of some Dynamic Link Libraries (DLLs) that must be installed. With others you can use software like Virtual Audio Cable (VAC) to route the audio from the SDR to the PC. Those packages that can directly interface with SDRs are shown in {{color|green|green}} on the Utility Monitoring Central website.
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| − | ==YouTube Videos==
| + | ; Chapter 5. Scheduled and Easy to Hear Stations |
| − | * These are YouTube links to videos that mention the following software packages. Note that due to the broad nature of the search, other links could also be here. If the software is not linked in any of the above sections, then see the Utility Monitoring Central [http://www.chace-ortiz.org/umc/software.html Software page] for links to the software itself.
| + | *[[Testing Your New Setup]] |
| − | * [https://www.youtube.com/results?search_query=Radiocom+6 Bonito Radiocom 6]
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| − | * [https://www.youtube.com/results?search_query=fldigi FLDigi]
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| − | * [https://www.youtube.com/results?search_query=code300-32 Hoka Code 300-32] | |
| − | * [https://www.youtube.com/results?search_query=JVComm JVComm32]
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| − | * [https://www.youtube.com/results?search_query=krypto500 Krypto500]
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| − | * [https://www.youtube.com/results?search_query=MixW MixW]
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| − | * [https://www.youtube.com/results?search_query=multipsk MultiPSK]
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| − | * [https://www.youtube.com/results?search_query=PC-ALE PC-ALE]
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| − | * [https://www.youtube.com/results?search_query=PC-HFDL PC-HFDL]
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| − | * [https://www.youtube.com/results?search_query=Rivet+java+software Rivet]
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| − | * [https://www.youtube.com/results?search_query=Seatty SeaTTY]
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| − | * [https://www.youtube.com/results?search_query=Sigmira Sigmira]
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| − | * [https://www.youtube.com/results?search_query=W-Code Wavecom W-Code]
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| − | == Are there other resources?==
| + | ; Chapter 6. References |
| | + | *[[HF Appendix]] |
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| − | Print magazines are not always the best place to go for this kind of information. Their long lead times (sometimes as much as 30-45 days) means that the data gets stale very quickly.
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| − | The [https://groups.yahoo.com/neo/groups/UDXF/info Utility DXers Forum] (UDXF) Yahoo group is an excellent place to help identify the mode and user of a particular signal. There are also specialized Yahoo groups (such as the one for [https://groups.yahoo.com/neo/groups/hfdl/info HFDL]) that can supply updated software or active frequencies. There are also ircchat sites (see <nowiki>irc://irc.starchat.net/wunclub </nowiki>) where you can ask questions, and get nearly immediate responses. These are often your best sources of information.
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| | [[Category:HF Topics]] | | [[Category:HF Topics]] |
| | + | [[Category:HF Signal Analysis and Decoding]] |
NOTICE: The rules about listening to signals not intended for you applies here. The contents of many signals might be considered sensitive by the party sending and the reception of such signals may be illegal in your country. The authors neither condone or encourage such acts
This document is designed to give utility listeners a sampling of the kinds of signals and sounds available on shortwave (HF) radio today along with information on the available equipment needed to understand, analyze or identify these signals. Our primary focus is to present the parameters that define the most commonly heard systems as an aid for utility monitors and not an exhaustive discussion of HF
digital signaling theory.
Digital Utility listening is inherently more difficult than regular shortwave listening. The possibility of decoding the signal received adds another level of complexity. This document is an attempt to describe to hobbyists what digital signals can be received and decoded, in addition to providing the more advanced listener with a little more technical data to identify an otherwise unknown signal.
Herein lies the basic problem with digital utility listening - lack of information. Many systems are used by Military or Diplomatic Services and information on the specifics of a particular mode are impossible to find, even from the manufacturer. Many are considered proprietary, but that doesn't mean that a signal can not be identified. With the proper tools a given signal can be identified via the way it sounds (aurally) or how it looks (visually). Most of the more expensive decoders that include some kind of signal analysis can ID a signal by bit-pattern or baud rate. Once a signal is identified there are many decoders that can print the traffic for you; however, keep in mind there may be various kinds of encryption in use with these signals. Encryption types include figure group or letter group messages and even random bit-masking or bit stream encryption, which looks like a continuous stream of random characters. You may often read the term "on-line" and "off-line" used in conjunction with various encryption schemes. Generally, off-line encryption is taken to mean groups of letters or numbers (most usually groups of five), whereas on-line schemes just appear as a continuous stream of random characters.
Keep in mind that you must be able to find a signal before you can apply the power of the decoder on the signal for identification and possible decoding. Most signals found on the airwaves today are obvious with easily distinguishable sounds, from chirping to two tone FSK to musical multitone MFSK, but as communication technology develops this will most likely change. It is safe to say that the more efficient a modulation/coding method is, the more noise like it must become. It has been said in some digital groups that "Any sufficiently advanced communication is indistinguishable from noise".
This document covers the following areas. Please click on the desired topic;
- Chapter 1. Receivers and PC Connections
- Chapter 2. How Do I Decode A Signal I Find on HF?
- Chapter 3. Modes and Sounds
- Chapter 4. Articles
- Chapter 5. Scheduled and Easy to Hear Stations
- Chapter 6. References