#!/usr/bin/env python3 """Generate the bandsaunter manual page from the settings table. The settings are described in exactly one place -- bandsaunter/settings.py -- so the manual cannot drift from the program. Every setting appears here with its command-line flag, its default, and the plain-language guidance that says what it is and when someone would change it. """ import sys from datetime import date from pathlib import Path sys.path.insert(0, str(Path(__file__).resolve().parent.parent)) import bandsaunter # noqa: E402 from bandsaunter import settings as st # noqa: E402 from bandsaunter.config import ScanConfig # noqa: E402 def esc(text: str) -> str: """Escape for troff: a leading dot or apostrophe is a request.""" out = text.replace("\\", "\\e") return "\n".join(("\\&" + ln if ln[:1] in (".", "'") else ln) for ln in out.split("\n")) def settings_section() -> list[str]: out = [] defaults = ScanConfig() for group in st.GROUPS: out.append(f'.SS {esc(group)}') for s in st.in_group(group): flags = " ".join(s.flags) if s.off_flags: flags += " / " + " ".join(s.off_flags) shown = st.format_value(s, getattr(defaults, s.key)) unit = f" ({s.unit})" if s.unit and s.kind not in ("bool",) else "" out.append('.TP') out.append(f'.B {esc(flags)}') out.append(f'{esc(s.label)} \\[em] {esc(s.help)}{esc(unit)}.') out.append('.br') out.append(f'Setting name \\fB{esc(s.key)}\\fR, ' f'default \\fB{esc(shown)}\\fR.') accepts = s.describe_range() if accepts: out.append('.br') out.append(f'Accepts: {esc(accepts)}.') if s.guidance: # Indented to the entry it belongs to, not back out to the # left margin, so an entry reads as one block. out.append('.RS') out.append('.PP') out.append(esc(s.guidance)) out.append('.RE') out.append('.PP') return out HEAD = r'''.\" Generated by packaging/make-man.py -- do not edit by hand. .TH BANDSAUNTER 1 "{date}" "bandsaunter {version}" "User Commands" .SH NAME bandsaunter \- scan, record and identify radio signals with an RTL-SDR .SH SYNOPSIS .B bandsaunter .RI [ command ] .RI [ options ] .br .B bandsaunter scan .BI \-r " RANGE" .RI [ options ] .br .B bandsaunter .RI "(no arguments: interactive menus)" .SH DESCRIPTION .B bandsaunter sweeps any set of frequency ranges with an RTL-SDR receiver, stops on signals that rise above the background noise, records them, and works out what kind of signal each one was. Morse is decoded to text and speech can be transcribed. .PP Ranges are given by hand or chosen from a built-in US band plan. There is no limit on how many may be scanned at once. .PP Captures that turn out to be noise, static or interference are discarded rather than saved, so what ends up on disk is transmissions rather than hiss. This is the behaviour of .B \-\-require\-signal and it is on by default. .PP Every setting can be given as a command-line option, set in the menus, or saved to a settings file; the three are the same list, described under .B SETTINGS below. .SH COMMANDS .TP .B scan Run a scan. Without .B \-r or .B \-b the interactive menus open instead. .TP .B bands Browse the built-in US band plan: amateur, marine, aviation, public service, business, railroad, GMRS/FRS, CB, ISM, weather, and more. .TP .B config Show or change the saved settings. .B "config KEY=VALUE" sets one and saves it, .B "config \-\-show" prints them all, .B "config \-\-describe KEY" explains one in full, and .B "config \-\-edit" opens the menus. .TP .B transcribe Transcribe existing recordings, or list which speech recognisers are installed with .BR \-\-engines . .TP .B waterfall Draw a waterfall for every recording in a directory that produced no readable words. See .B WATERFALLS below. .TP .B devices List attached receivers. .TP .B profiles List saved profiles. .TP .B adsb Listen to aircraft on 1090 MHz and write down everything they say. See .B AIRCRAFT below. .TP .B flights Read an ADS-B log back: the report, the map for Google Earth and the animation. See .B AIRCRAFT below. .TP .B analyze Identify a signal in an already-recorded file, decode Morse from it, or write out the picture it turns out to be. .SH OPTIONS .TP .BI \-r " RANGE\fR, \fP" \-\-range " RANGE" A frequency range to sweep, such as .IR 144M\-148M . Repeatable, and a comma-separated list is accepted. See .B ENTERING FREQUENCIES below. .TP .BI \-b " KEY\fR, \fP" \-\-band " KEY" A band-plan preset, such as .IR gmrs " or " marine\-vhf . Repeatable. .B bandsaunter bands lists them. .TP .BI \-\-mode " MODE" Force one demodulator for every range: nfm, wfm, am, usb, lsb, cw or raw. Without this each range is demodulated according to what the signal turns out to be, which is normally what you want. .TP .BI \-p " NAME\fR, \fP" \-\-profile " NAME" Start from a saved profile instead of the saved default settings. .TP .BI \-\-save\-profile " NAME" Save the settings this run would have used, under that name, and exit. .TP .B \-\-save Save the settings this run would have used as the new defaults, and exit. .TP .B \-\-no\-config Ignore the saved settings file and start from the built-in defaults. .TP .B \-\-simulate Use a synthetic receiver instead of real hardware. Everything else behaves normally, so the program can be tried out with no dongle attached. .TP .B \-\-dry\-run Print the sweep plan \[em] every tuner step and how long a pass will take \[em] and exit without receiving anything. .TP .B \-\-keep\-carriers Also record steady unmodulated carriers, which are otherwise discarded as having no content. Useful for beacon hunting or for tracking down a source of interference. .SH SETTINGS Each of these can be given as a command-line option, changed in the menus under .BR "bandsaunter config" , or written into the settings file. The command line wins for one run; the settings file is what every run starts from. ''' TAIL = r'''.SH ENTERING FREQUENCIES Frequencies may be written with a unit or without: .IR 146.52M ", " "146.52 MHz" ", " 146520k ", " 146520000 . A bare number under 10000 is read as megahertz, since that is how people write frequencies. .PP A range is a pair: .IR 144M\-148M ", " 144\-148M " (the unit carries over), " "144M to 148M" ", " .IR 144M..148M . A single frequency on its own is treated as a narrow range around it. .PP A step and a demodulator may be attached: .I 144M\-148M/25k@nfm sweeps in 25 kHz steps and demodulates narrowband FM. .PP Several may be given at once, separated by commas, and .B \-r may be repeated. There is no limit on how many ranges a scan may cover. .SH BAND PLAN .B bandsaunter bands lists over a hundred presets from the US band plan, each carrying the right step size and demodulator for that service, so .B "\-b gmrs" is enough to scan GMRS properly. .PP Presets that stand for several others expand automatically: .I all\-cw sweeps every Morse segment of every amateur band, and .IR 2m\-complete ", " 70cm\-complete and their like sweep a whole amateur band end to end rather than one segment of it. .PP The same plan names what is heard. Beside every frequency on the display, and in the line\-per\-hit output, is the band it falls in: a signal at 421 MHz is labelled .IR "70 cm Amateur" , one at 462.5625 MHz is .IR "GMRS / FRS" , and 162.55 MHz is .IR "NOAA Weather Radio" . Where several allocations overlap, the narrowest wins, because it says the most \[em] 146.52 MHz is named as the 2 m simplex calling channel rather than as the whole 2 m band. The name is written into each recording's sidecar as well, so it stays with the capture. .SH LOCK-OUTS Every receiving setup has a few frequencies not worth stopping on: a pager transmitter down the road, a nearby data link, or a spurious signal the receiver manufactures itself. Locking one out makes the scan skip it. .PP Pressing .B l during a scan locks out whatever is being received. Unless .B \-\-no\-save\-lockouts is given, it is written back to the settings file the run started from, so it stays locked out on later runs. Only the lock-out list is written back \[em] options given on the command line for a single run stay one-off. .PP Lock-outs can also be given directly, several at a time, as single frequencies or as spans: .PP .RS .EX bandsaunter scan \-r 144M\-148M \-\-lockout "162.55M, 450M\-455M" .EE .RE .PP A single frequency is widened by .BR \-\-lockout\-width ; a span is used exactly as written. .PP Two runs never write anything back. .B \-\-no\-config has no settings file to write to, since the point of it is to leave the saved settings alone; and .B \-\-simulate is looking at an invented band, whose frequencies would be nonsense in a real settings file. Both still lock out for the run in hand, and say so. .SH THE LIVE DISPLAY The display is redrawn in place several times a second, so it has to fit the window. On a short terminal the optional parts are given up in order \[em] the spectrum row, then the list of recorded signals, then the key hints, and last of all the receiver panel, which says nothing that changes. What is never given up is the sweep line and, while one is running, the recording. .PP Resizing the window redraws everything from a blank screen. The frame that was on it was drawn for a window that no longer exists, and the text above it has been reflowed by the terminal in any case, so what was printed before the scan started \[em] the sweep plan and the settings summary \[em] scrolls away at that point. .PP .B \-\-plain prints one line per hit instead and needs none of this, which is what to use when the output is going into a pipe or a log. .SH KEYS DURING A SCAN .TP .B q Stop. .TP .B p Pause and resume. .TP .B s Abandon this recording and resume sweeping. .TP .B l Lock out this frequency, now and in future runs. .TP .B "+ \fRand\fB \-" Raise or lower the squelch threshold by 1 dB. .SH OUTPUT Recordings are named .IR frequency \-\- date _ time \- modulation .wav , with the frequency padded to four digits so that an ordinary directory listing sorts by frequency. Beside them are the run log, as JSON lines and as CSV, and optionally a transcript per recording and the raw samples. .PP With .B \-\-combine every transmission on one frequency is appended to a single growing file for that frequency, with a spoken date and time before each one, so a scan can be played back as a recording of that channel rather than clicked through as hundreds of fragments. .SH TRUNKED SYSTEMS Police, fire and large business radio in the US mostly runs on .IR trunked systems. Instead of giving each department its own frequency, the system owns a pool of channels and hands one out for each conversation as it happens. To make that work, one frequency in the pool is given over entirely to a data stream that runs day and night, telling every radio in the fleet where to go next. That frequency is the .IR "control channel" . .PP A control channel is the worst thing a scanner can find. It is loud, it is perfectly steady, it never stops, and there is nothing on it to listen to \[em] just a harsh buzz. A scanner without special handling parks on it for the whole record limit, saves the file, and then finds it again on the next sweep, for as long as it is left running. .PP bandsaunter recognises one from the shape of the signal, names the system on screen, deletes what it captured and moves on, usually within a second or two. What it looks for is a constant\-envelope data stream that never pauses, at a symbol rate belonging to a known trunking standard: .RS .PP 3600 baud two\-level \[em] Motorola SMARTNET / SmartZone (Type I and II). .br 9600 baud two\-level \[em] EDACS and ProVoice. .br 1200 baud two\-level \[em] MPT\-1327. .br 4800 baud four\-level \[em] P25 or DMR Tier III. .br 2400 baud four\-level \[em] NXDN and NEXEDGE. .RE .PP The first two are recognised at once: nothing else transmits at those rates without pausing. The others share their shape with an ordinary digital voice call on the same system, so they are only called a control channel once the carrier has run unbroken for .B \-\-control\-seconds (20 s by default) \[em] long enough that a real conversation would have taken a breath. Raise that figure if digital voice calls are being skipped by mistake. .PP Being inside a band where trunking is common raises confidence but is never required: trunking is licensed on business pairs all over the spectrum. .PP Use .B \-\-keep\-control to record control channels anyway, which is what you want if you are feeding them to a decoder. Use .B \-\-lockout\-control to have each one written into the lock\-out list as it is found, so the scanner stops looking at it at all; with .B \-\-save\-lockouts on, that list survives a restart. .SH TRANSCRIPTS Anything the content check identifies as voice is passed to a speech recogniser, and the words are written to a .I _transcription.txt beside the recording. Only voice: running a recogniser over Morse or a data burst costs seconds and produces nothing. .PP One transcript per transmission, and none is ever overwritten \[em] the timestamp is part of the name, so two overs on one frequency cannot land on the same file. .PP With .B \-\-combine there is one recording per frequency, so there is one transcript per frequency, and each over is appended to it with the time it was heard. An unattended receiver keeps adding to that file night after night rather than starting it over. .PP A capture with nothing recognisable in it produces no file at all, rather than a directory of placeholders. No voice-activity filter runs inside the recogniser \[em] one throws away the single-word overs between transmissions, which on a scanner are the replies worth having. Instead the whole capture is asked once whether anything in it rises above its own noise, and refused before a recogniser sees it if nothing does. That check can veto a capture but never trim one, so a short reply in the middle of a quiet channel survives it. .PP .BR saunterbrowse (1) reads these back, and lists any callsigns it finds in them with the licence they belong to. .PP A callsign in a transcript is not written the way it is printed. A recogniser has never heard of the phonetic alphabet: it writes what the words sounded like, breaks the callsign wherever the speaker paused, joins the words back up, hyphenates them, or drops a hesitation into the middle of the run. So "KU 0W", "kilo uniform zero whiskey", "Whiskey\-One\-Alpha\-Whiskey", "WhiskeyOneAlphaWhiskey" and "whiskey one alpha, uh, whiskey" are all read back as the callsigns they are, and "alfa", "juliett" and "whisky" count alongside the official spellings. .PP Two shapes are recognised. An amateur callsign is a prefix, a district digit and a suffix; everything else the FCC licenses is written the other way round, the letters first and then the digits, so WQVF960 and WXG204 are read as the GMRS and business licences they are. .PP Nothing is joined across a slash: a suffix says where the station is, not what it is called, so .I W1AW/B is W1AW. .SH WATERFALLS Most of what a scanner records cannot be turned into words: a data burst, a keyed carrier, a pager, a control channel, a stretch of something unidentified. A waterfall says something about every signal there is, because it shows the shape of the thing rather than its meaning \[em] how wide it is, how long it lasted, whether it was keyed, swept, hopping or steady, and whether it was one signal or three side by side. .PP So every capture that produced no readable words is drawn beside the audio as a PNG: no voice, or voice the recogniser came back from with fewer than .B \-\-waterfall\-min\-chars characters, which is what a recogniser handed something that is not speech reliably does. Time runs down the picture and frequency across it, with the frequency scale on top, the seconds down the left and a caption underneath saying what the capture was. .PP A capture with Morse in it is never counted as readable, however long the transcript. A station identifying itself in CW over an FM carrier is transcribed as a string of digits, one per tone, which clears any bar and says nothing; the ident is in the Morse text and the signal is only visible as a picture. .PP The caption also says what the picture is *of*, and that matters. Where the raw IQ was kept this draws the radio spectrum around the tuned frequency, which is the waterfall an operator would have been watching. Where only the audio was kept \[em] the usual case, since IQ is off by default \[em] it draws the demodulated audio instead: after an FM detector the frequency axis is no longer radio frequency, and a picture that did not say so would be a lie told in a convincing font. .PP .B bandsaunter waterfall does the same for a directory already recorded, drawing only what cannot be read unless .B \-\-all is given, and skipping what it has already drawn unless .B \-\-redraw is. .B \-\-check\-morse runs the CW decoder over the recordings it was about to skip, for sidecars written before the decoder could hear an ident over an FM carrier, and draws \[em] and records the ident in \[em] the ones that have one. .SH CW AND IDENTIFICATION Every capture is offered to a CW decoder once it has finished, whatever the classifier made of it. Most of the Morse on the air is not a conversation: it is a repeater, a beacon or an unattended transmitter saying who it is and stopping, which is four to six characters and over in a second or two. That burst is a fraction of a capture named after whatever filled the rest of it, so waiting for the label to say "CW" missed it. .PP Nor does that station key its carrier. On the land-mobile bands the carrier stays up and the ident is an audio tone keyed inside it, which a detector looking for a keyed carrier sees as a carrier that never stops. So the recorded audio is searched as well, a few seconds at a time, because the decoder takes its tone and its key-down threshold from the whole of whatever it is handed: a half-minute recording with five seconds of keying in the middle measures both from the other twenty-five. A mark far longer than any dash is read as the transmission the ident was sent over rather than as a character the window sliced, which is what used to take the first and last letter of every such ident \[em] and with them the callsign, one word with no gap in it to survive the drop. .PP A reading made only of one-element characters is refused. E and T are the only two, so a decode of nothing but those can hardly be wrong \[em] there is nothing in it to get wrong \[em] and no station has ever identified itself that way. .PP Short is therefore the normal case rather than the awkward one. A decode of two or three characters is believed on its timing alone \[em] every element within a third of a unit of one or three, every character resolving to something in the table, and the keyed tone standing at least 20 dB above the rest of its band. That last one is what separates an ident from a blip: with four elements the dot length is fitted to those very elements, so noise lands on the grid as neatly as keying does, and only the tone tells them apart. One keyed element is refused, because a single pulse is an E or a T whether a person sent it or the squelch opened on a click. .PP The other half of a short decode is knowing what was cut off. A capture opens when the squelch does, which is in the middle of an element as often as not, and half a character is not a smaller reading of what was sent \[em] it is a different one, and a K with its first dash missing is an A. So the character at a sliced end is dropped, and so is the rest of the word it was in, because what is left of that word can read as a whole one: .I K1AA caught halfway through is .IR K1A , which belongs to somebody else. The full text is still reported; it is the identification that is held to the stricter standard. .PP What survives goes to the same callsign lookup and the same map as a spoken one. Word gaps in Morse are not joined across, because the sender chose them: .I "KU0W K" is a station signing off, not a callsign one letter longer. .SH DECODING DATA A great deal of what a scanner finds is not speech. Doorbells, tyre\-pressure sensors, weather stations, remote controls, paging and packet radio all carry words or numbers that a receiver can read, and .B bandsaunter reads them. .PP Whatever the modulation, a data signal comes down to the same shape once it has been sliced: a train of alternating runs whose lengths carry the information. On\-off keying gives that directly \[em] the carrier is up or it is down \[em] and two\-level FSK gives the same thing from the discriminator, one tone or the other. So both are reduced to runs and everything after that is shared. .PP What the runs mean is the line code, and it is worked out from the runs alone rather than being configured: .TP .B PWM The pulse carries the bit and the gap or the period holds still. Nearly every cheap 433 MHz remote, and everything built on an EV1527 or PT2262. .TP .B PPM The pulse holds still and the gap carries the bit. The other half of the same market. .TP .B Manchester Every bit is a transition in the middle of its own period, so runs come in only two lengths. .TP .B NRZ The level is held for as many symbol periods as there are bits. What a framed protocol sits on top of. .PP Four\-level FSK \[em] C4FM, as P25, DMR and NXDN use it \[em] is recognised as such and read as symbols rather than being sliced down the middle, which would give bits that mean nothing. Where a frame sync word appears the system is named outright. .SH PROTOCOLS THAT CAN BE READ IN FULL Two carry their own framing and checksums, so a frame either passes or it does not, and one that passes is not a guess. .TP .B POCSAG Paging, at 512, 1200 or 2400 baud. The rate is not announced anywhere in the signal, so all three are tried and the one whose sync word appears is the right one. Each codeword is checked, and a single bit error is corrected, against the BCH code the standard puts there for the purpose. The address, the function letter and the message text are all reported. .TP .B "AX.25 / APRS" Amateur packet on 1200 baud AFSK. The frame check has to come out right before a frame is reported at all. The sender's callsign, the digipeater path and the payload are shown \[em] and the callsign goes onto the map with the rest. .SH BELIEVING A DECODE A decoder that always returns something is worse than useless: noise sliced at a threshold produces runs, and runs produce bits. Three things guard against that. .PP The runs have to quantise to the line code's own grid, and a decode whose runs are scattered is thrown away. Most of the bursts in a capture have to decode the same way, because a data signal is data all the way through and one lucky window among eight is a coincidence. And, much the strongest, the packet has to repeat \[em] these transmitters send the same thing three to ten times over, and bits that come back identical every time did not come from noise. .PP A bare reading with none of that behind it, where the runs merely happened to land on a grid, is reported as nothing at all rather than as a bit string with a low number beside it that somebody will read anyway. .PP A decode that does have repeats or a checksum behind it outranks the content check: a burst of keying demodulated as FM audio is a buzz, and the speech detector likes a buzz, but a frame whose own checksum came out right is not a statistic. .SH PICTURES Three of the things a receiver can hear are images rather than sounds. All three are analogue, all three encode brightness as a frequency, and all three arrive as the audio the scanner already records \[em] so they are looked for in every recording and written out as PNG beside it. .TP .B SSTV Slow-scan television, on 14.230 MHz and 144.5 MHz and wherever else amateurs send it. A transmission opens with a VIS header that says which mode follows, and that header is what is looked for: no header, no picture. Martin M1 and M2, Scottie S1, S2 and DX, and Robot 36 and 72 are decoded, in colour. .TP .B "APT" The NOAA weather satellites on 137 MHz, which spend a fifteen-minute pass sending one continuous picture. A 2400 Hz tone carries the brightness, two lines a second, 2080 words to a line, with both of the satellite's sensors in every line. The whole frame is written, and each sensor again on its own. .TP .B "HF fax" The weather charts the shortwave stations have sent for decades, in single sideband between 2 and 20 MHz. A transmission opens with a phasing signal \[em] twenty or so lines that are black but for a pulse at the start of each \[em] and that is what says where a line begins and how long one is. .PP None of the three is guessed at, which is what makes it safe to try them on every recording: each is recognised by a header or a phasing signal that nothing else on the air sends. A decoder without one draws static beautifully, and a directory of beautifully rendered static is worse than an empty one. .PP A picture keeps its capture whatever the content check made of it. A satellite is a steady tone with a wobble on it and an SSTV transmission is a whistle: neither is speech and neither has symbol structure, so both were being thrown away as "no signal content" having already been recognised. .PP Pictures take minutes rather than seconds \[em] two minutes for SSTV, fifteen for a satellite pass \[em] so .B \-\-record has to be long enough or what arrives is the top of one. A partial picture is kept and labelled as partial rather than discarded. .PP .BR saunterbrowse (1) marks these in the list and gives the path of the file. .PP GRIB, which is sometimes asked about in the same breath, is not a modulation: it is the binary format the weather models are published in, and it travels by satellite data link and by e-mail rather than as something a receiver can demodulate. Where a decoded byte stream begins with its magic number it is named as such; nothing here fetches or renders one. .SH AIRCRAFT .B bandsaunter adsb parks the receiver on 1090 MHz and reads the Mode S extended squitter that every airliner overhead broadcasts twice a second: the aircraft's address, its callsign, its altitude, its position and its speed, unencrypted, to nobody in particular. .PP It is a command of its own because ADS-B does not fit through the scanner. The signalling is a megabit a second, which needs at least two megasamples a second of raw receiver output; the scan path decimates everything to a channel twelve and a half kilohertz wide long before any decoder sees it. .PP Every frame carries a 24-bit checksum, so there is no threshold here and nothing to disbelieve: a frame either passes or is dropped. A position takes two frames \[em] the encoding sends a fraction of a zone, and one frame alone is ambiguous by hundreds of miles \[em] so an aircraft is placed once an even and an odd frame have both arrived, about a second apart. .PP An aircraft is overhead for four minutes and then gone, so everything heard is written down as it arrives: a JSON Lines log, one object per frame, in .I adsb_