Signal Identification
From HFUnderground
Contents |
Why is this Guide here?
The goal of this Wiki is to help people ID sounds and signals they might come across on the radio, primarily in the HF (3000 to 30000 kHz) and MW (300 to 3000 kHz) bands. Of course not all possible signals can be identified, and certainly they cannot all be presented here. So the IDs will start with the most common modes and move forward from those. As signals to be IDed are presented and hopefully identified on the HFUnderground HF Mystery Signals board they will be added to these lists, assuming they were not already here.
With the advent and proliferation of SDRs to the hobby of shortwave listening, and the often associated wideband waterfall / spectrum displays, hobbyist are now more likely to notice short duration, transient, signals. Signals are now visually presented that in the past would not have been noticed at all unless the listener just happened to be tuned to the right random frequency when the short duration signal occurred. This has had the affect of raising the probability of reception of any given signal type, regardless of duration. Further, these waterfalls and spectrum images can be used to ID specific modes of operation, as different techniques often have very different visual signatures.
Today's online receiver nodes (from services like Globaltuner.com, SDR-Radio.com, and websdr.org) mean that more people than ever potentially have access to monitor the HF spectrum. Often people with no prior exposure to HF radio or shortwave listening first gravitate to these kinds of services, as they take no investment in equipment to start using.
In general the use of analogue voice and manual communications modes on the HF and MW bands is on the decline, replaced with digital and data modes. The use of other than communications modes, such as ionospheric sounders and HF radars, seems to be at an all-time high. For the new listener, or for more experienced listeners without the proper tools, identifying some of these modes and signals can be a challenge.
How to submit a signal for ID?
Go to the HFUnderground HF Mystery Signal board and follow the guidelines presented there for posting. Assuming the signal is IDed there, and it is not already on the list here, it will likely be added to this list.
How to use this Identification Guide?
If you look at each segment of the guide you will see it is divided into two types of signals, "Non DATA Signals" and "DATA Signals". Each section is further broken down into sub categories.
Non DATA Signals are modes that do not carry what is traditionally thought of as digital data. This will be analogue voice modes, traditional Morse Code transmissions, and signals along those basic lines. Radars and Ionosondes have also been included in this segment, as they are not typically DATA transmissions.
DATA Signals are pretty much everything else. If it goes through a modem or is computer generated before being transmitted to the open air it will probably be included in the DATA Signals section. This includes digital voice modes, including many encrypted modes. The DATA Signals section is loosely broken down into the type of modulation used for the data, FSK, MFSK, PSK, etc.
Various image modes, such as HFFAX, SSTV, etc, are included in the DATA Signals, even when they are not digital in nature. Despite many of these types having analogue backgrounds most are generated by computer today.
Basic information shown
"Mode" is simply a generally accepted name of the technique. This may not be the only designator used for that specific technique. For example, traditional "AM" can also be described as "Double sideband with full carrier", and "A3E". In such a case these other designations may be included on the Mode Specific page. If a Mode Specific page exist for a mode you can access it by clicking on the name in the Mode column. The Mode Specific page will generally contain more detailed information than can be included in this initial chart.
"Frequency Range (kHz)" is the range of frequencies where one might find this specific mode in use. For many modes this can be a very wide range, but other modes might be very limited in range. Remember this guide is MW and HF specific and may not consider usage in other frequency ranges.
"Bandwidth (kHz)" is the normally occupied bandwidth of the signal, as might be seen on a waterfall or spectrum display. Unless you include the power point for the measurement (3 dB, 6 dB, 10 dB, 20 dB, etc) this is an approximate value only. Because of this very strong signals can appear wider than very weak signals, even if both signals are actually using the same bandwidth. The goal here is to provide something that might help identification, not to define a technical specification for the mode.
"Shift (kHz)" is something that only applies to certain types of DATA or digital transmissions. It will be used to define the spacing for visually definable tones or data channels in a transmission.
"Number of Tones" is applicable to certain types of DATA or digital transmissions. It will be used to indicate the number of visually definable tones or data channels in a transmission.
"Key Features" will be selected features that can help identify the signal, or at least narrow down the candidate pool. Ideally it will be one or two visually distinctive features that can be seen on a waterfall or spectrum display, but these might also be auditory features.
"Sources" are the most likely source for this transmission mode, if known.
"Recording" will link to an audio recording of the mode. Further recordings, both audio and video, may be present on the Mode Specific page.
"Spectrum Image" is a 200 pixel wide expandable thumbnail image of the signal, typically either the spectrum or a waterfall / histogram of some kind. Typically the full size version of this images is at least 640 x 480.
Signals
Non DATA Signals
Communications Modes
Mode | Frequency Range (kHz) | Bandwidth (kHz) | Shift (Hz) | Number of Tones | Key Features | Sources | Recording | Spectrum Image |
---|---|---|---|---|---|---|---|---|
AM | All Frequencies in the HF Range | Typically 2.6 to 10.0 kHz, can be wider or narrower | Not Applicable | Not Applicable | Carrier present in center of signal, audio typically mirrored left and right of the carrier | World wide | AM recording link here | |
CW
(Morse Code) | All Frequencies in the HF Range | Very narrow, potentially less than 50 Hz | Not Applicable | Not Applicable | Line or broken line on the waterfall, no sidebands, may show wider "key clicks" at the start and stop of each dot and dash | World wide | CW recording link here | |
LSB | All Frequencies in the HF Range | Typically 2.4 to 3.0 kHz, can be wider or narrower | Not Applicable | Not Applicable | No carrier present in Spectrum, audio typically bunched to towards the right (low audio frequency) | World wide | LSB recording link here | |
USB | All Frequencies in the HF Range | Typically 2.4 to 3.0 kHz, can be wider or narrower | Not Applicable | Not Applicable | No carrier present in Spectrum, audio typically bunched to towards the left (low audio frequency) | World wide | USB recording link here |
Non Communications Modes
Mode | Frequency Range (kHz) | Bandwidth (kHz) | Shift (Hz) | Number of Tones | Key Features | Sources | Recording | Spectrum Image |
---|---|---|---|---|---|---|---|---|
16 x 64 Sounder (nickname, official name or designation not known) | Below 4000 to above 30000 observed | 2.5 kHz | Not Applicable | Not Applicable | FMCW transmission, changes sweep rates in 16 steps, resulting in 16 different sounds per transmission, a pilot tone may precede each rate change but is not always present | Unknown | Media:16x64_sounder.mp3
16 x 64 sounder recording | |
PLUTO radar (possible offical name, PLUTO II, suggested by open source documents) | 8000 to 38000 | 3 to 40 kHz, depending on specific operating conditions | Not Applicable | Not Applicable | FMCW transmission, presenting a wide signal equal to the swept (chirped) width, sweep rate creates a pulsed sound affect | British Sovereing base of Akrotiri, Island of Cyprus | PLUTO recording link here |
Need to put some kind of break here, a line or something, to sep out the Non DATA from DATA
Probably need to put a desription of what is meant by DATA Signals in this area.
DATA Signals
FSK Modes
MFSK Modes
Mode | Frequency Range (kHz) | Bandwidth (kHz) | Shift (Hz) | Number of Tones | Key Features | Sources | Recording | Spectrum Image |
---|
PSK Modes
Mode | Frequency Range (kHz) | Bandwidth (kHz) | Shift (Hz) | Number of Tones | Key Features | Sources | Recording | Spectrum Image |
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SELCAL Modes
Mode | Frequency Range (kHz) | Bandwidth (kHz) | Shift (Hz) | Number of Tones | Key Features | Sources | Recording | Spectrum Image |
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Image Modes
Mode | Frequency Range (kHz) | Bandwidth (kHz) | Shift (Hz) | Number of Tones | Key Features | Sources | Recording | Spectrum Image |
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