.\" Generated by packaging/make-man.py -- do not edit by hand.
.TH BANDSAUNTER 1 "2026-08-22" "bandsaunter 2026-08-22_04" "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 devices
List attached receivers.
.TP
.B profiles
List saved profiles.
.TP
.B analyze
Identify a signal in an already-recorded file, or decode Morse from it.
.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.
.SS Dwell and recording
.TP
.B --record --record-seconds
Record for \[em] longest one signal may hold the receiver (0 = no limit) (s).
.br
Setting name \fBrecord_seconds\fR, default \fB30 s\fR.
.br
Accepts: at least 0.
.RS
.PP
How long one signal may keep the receiver before the sweep moves on. Set it to 0 and a transmission is followed until it actually ends, which is what you want for listening to conversations. Give it a number if you would rather sample a busy band widely than sit on the first station that comes up.
.RE
.TP
.B --hang --hang-seconds
Wait for quiet \[em] quiet time before the sweep resumes (s).
.br
Setting name \fBhang_seconds\fR, default \fB2 s\fR.
.br
Accepts: at least 0.
.RS
.PP
How much silence means 'they have finished talking'. People pause between sentences, and two people taking turns leave a gap every time the conversation changes hands; anything shorter than this is recorded straight through, so an exchange stays in one file. Raise it if conversations keep getting split into pieces, lower it if the scanner sits on dead air.
.RE
.TP
.B --max-record
Absolute limit \[em] ceiling on one capture, even when 'Record for' is 0 (s).
.br
Setting name \fBmax_record_seconds\fR, default \fB900 s\fR.
.br
Accepts: at least 0.
.RS
.PP
A safety stop. With no record limit set, a stuck transmitter or a continuously modulated data channel would record until the disk filled, and this is where that stops. Only worth changing if you are deliberately capturing something very long; 0 removes the stop entirely.
.RE
.TP
.B --min-record
Discard shorter than \[em] throw away captures shorter than this (s).
.br
Setting name \fBmin_record_seconds\fR, default \fB0.5 s\fR.
.br
Accepts: at least 0.
.RS
.PP
Recordings shorter than this are deleted instead of kept. A click of static or a passing car's ignition noise can hold the squelch open for a fraction of a second, and this is what keeps those out of the directory. Raise it if you are collecting lots of tiny useless files; lower it if you are chasing very short transmissions such as data bursts or single-word replies.
.RE
.TP
.B --revisit
Ignore again for \[em] hold-off before the same frequency can be recorded again (s).
.br
Setting name \fBrevisit_seconds\fR, default \fB8 s\fR.
.br
Accepts: at least 0.
.RS
.PP
After recording a frequency, ignore it for this long. One busy repeater can otherwise take over the whole scan, recorded again and again while everything else goes unheard. Lower it if you want everything from one channel; raise it if one talkative frequency is drowning out the rest of the band.
.RE
.PP
.SS Detection
.TP
.B -t --threshold
Squelch threshold \[em] margin over the noise before a signal counts as present (dB).
.br
Setting name \fBthreshold_db\fR, default \fB10 dB\fR.
.br
Accepts: at least 0.5.
.RS
.PP
How much louder than the background hiss something must be before the scanner stops on it. This is the squelch knob. Too low and it stops on noise; too high and it walks past quiet stations. If you are getting nothing at all, try lowering it a few dB; if you are recording static, raise it.
.RE
.TP
.B --dwell
Dwell per step \[em] how long the sweep listens at each tuner position (s).
.br
Setting name \fBdwell_seconds\fR, default \fB0.05 s\fR.
.br
Accepts: at least 0.005, at most 5.
.RS
.PP
How long the receiver listens at each tuning position while sweeping. A short dwell sweeps faster but can miss a transmission that starts and ends between visits; a long one hears more of what is there but goes round the band slowly. The default is a good compromise for voice traffic.
.RE
.TP
.B --resolution
Sweep resolution \[em] FFT bin width while sweeping (Hz).
.br
Setting name \fBresolution_hz\fR, default \fB3 kHz\fR.
.br
Accepts: at least 100.
.RS
.PP
How finely the sweep divides the spectrum when looking for signals. Finer resolution separates two stations sitting close together and finds weak narrow ones, but takes longer to compute. Worth making finer if you are scanning a crowded band of narrow channels.
.RE
.TP
.B --detector
Detector \[em] peak-hold catches bursts; averaging is quieter.
.br
Setting name \fBdetector\fR, default \fBpeak\fR.
.br
Accepts: one of: peak, avg.
.RS
.PP
How the sweep decides how strong each part of the band was. Peak-hold remembers the loudest instant, so it catches a transmission that starts and stops during the dwell, which is what you want for scanning. Averaging is quieter and steadier, and is better when you want a clean picture of the band rather than to catch every burst.
.RE
.TP
.B --detector-bias
Detector bias \[em] override the computed noise-peak offset (blank = automatic) (dB).
.br
Setting name \fBdetector_bias_db\fR, default \fBautomatic\fR.
.br
Accepts: at least 0.
.RS
.PP
A correction for the fact that peak-hold makes plain noise look stronger than it is, which would otherwise trigger the squelch on nothing. It is worked out automatically from the detector and the sweep settings, and there is normally no reason to set it by hand.
.RE
.TP
.B --squelch-margin
Squelch hysteresis \[em] how far below the threshold a signal may drop before it counts as gone (dB).
.br
Setting name \fBsquelch_margin_db\fR, default \fB3 dB\fR.
.br
Accepts: at least 0.
.RS
.PP
Once a signal has been found, it may drop this far below the squelch threshold before being counted as gone. Without it a station sitting exactly at the threshold would flicker on and off, chopping the recording into fragments. Raise it if recordings of weak stations keep breaking up.
.RE
.TP
.B --adaptive-floor / --no-adaptive-floor
Smooth the noise floor \[em] average the measured floor across sweeps.
.br
Setting name \fBadaptive_floor\fR, default \fByes\fR.
.RS
.PP
Learns what the background noise looks like across several sweeps rather than judging from one. It makes the squelch steadier, especially where the noise level varies across the band. Turn it off only if you are watching a band where the noise itself changes fast and you want the scanner to react immediately.
.RE
.TP
.B --max-detections
Signals per step \[em] how many separate signals one tuner position may report.
.br
Setting name \fBmax_detections_per_step\fR, default \fB4\fR.
.br
Accepts: at least 1.
.RS
.PP
The sweep can see several stations at once in the chunk of spectrum it is looking at, and this is how many of them it will queue up. Raise it in a crowded band where you are missing simultaneous transmissions; lower it if you would rather the scanner keep moving.
.RE
.TP
.B --probe
Probe length \[em] look at a signal for this long before choosing a demodulator (s).
.br
Setting name \fBprobe_seconds\fR, default \fB0.4 s\fR.
.br
Accepts: at least 0.05, at most 3.
.RS
.PP
Before recording, the scanner listens briefly to work out what kind of signal it is, so it can pick the right way to decode it. Longer is a more reliable guess but delays every recording slightly. The listen is not wasted: it is kept and played into the start of the recording.
.RE
.PP
.SS What counts as a signal
.TP
.B --require-signal / --keep-everything --no-require-signal
Check for content \[em] only keep captures that carry voice, CW or data.
.br
Setting name \fBrequire_signal\fR, default \fByes\fR.
.RS
.PP
Judge each capture and throw away anything that turns out to be noise, static or interference rather than a real transmission. This is the single setting that decides whether the recordings directory is full of things worth listening to or full of hiss. Turn it off only if you want everything that breaks squelch, however empty.
.RE
.TP
.B --accept
Record these \[em] which kinds of content are worth keeping.
.br
Setting name \fBaccept\fR, default \fBvoice, cw, digital\fR.
.br
Accepts: one of: voice, cw, digital, trunk, carrier, noise.
.RS
.PP
Which kinds of transmission are worth keeping: speech, Morse, data, trunking control channels, plain unmodulated carriers, and noise. Most people want voice, cw and digital. Add carrier if you are hunting beacons or interference sources, trunk if you are collecting control channels for a decoder, and noise only for diagnosing why nothing is being recorded.
.RE
.TP
.B --min-signal-score
Minimum confidence \[em] confidence needed to keep a capture.
.br
Setting name \fBmin_signal_score\fR, default \fB0.45\fR.
.br
Accepts: at least 0, at most 1.
.RS
.PP
How certain the content check must be before a recording is kept, from 0 to 1. Lower it if real transmissions are being discarded, since weak or noisy signals score lower. Raise it if borderline rubbish is still getting through.
.RE
.TP
.B --min-voice-score
Minimum speech score \[em] how speech-like audio must be to count as voice.
.br
Setting name \fBmin_voice_score\fR, default \fB0.45\fR.
.br
Accepts: at least 0, at most 1.
.RS
.PP
How speech-like audio has to sound before it is called voice. Speech has a pitch that moves and a rhythm of syllables; a steady tone or a hum does not. Lower it if quiet or distorted speech is being missed, raise it if music, hum or engine noise is being recorded as if it were someone talking.
.RE
.TP
.B --verify-every
Re-check every \[em] how often a live capture is re-examined (s).
.br
Setting name \fBverify_seconds\fR, default \fB1.5 s\fR.
.br
Accepts: at least 0.2.
.RS
.PP
How often a recording in progress is re-examined to see whether it is still carrying anything. Checking often releases the receiver quickly when a channel turns out to be holding static; checking rarely costs less processing.
.RE
.TP
.B --verify-max
Give up after \[em] how long a capture has to show any content (s).
.br
Setting name \fBverify_max_seconds\fR, default \fB6 s\fR.
.br
Accepts: at least 0.5.
.RS
.PP
How long a recording gets to prove it contains something. If nothing recognisable has appeared by then it is abandoned and deleted, and the sweep moves on rather than sitting on an open but empty channel.
.RE
.PP
.SS Trunking
.TP
.B --skip-control / --keep-control --no-skip-control
Skip trunk control channels \[em] spot a trunked system's control channel and move straight on.
.br
Setting name \fBskip_control\fR, default \fByes\fR.
.RS
.PP
Trunked radio systems -- the kind police, fire and large businesses use -- keep one frequency transmitting a data stream around the clock. It tells the radios which channel to jump to for each conversation; it carries no speech and it never goes quiet. To a scanner it looks like a very strong, very interesting signal, so without this setting the receiver parks on it, records the whole record limit of buzzing, and finds it again on the next sweep. With this on it is recognised within a second or two, named on screen, and skipped. Leave it on unless you are deliberately collecting control channel data to feed to a decoder.
.RE
.TP
.B --control-seconds
Control channel patience \[em] unbroken carrier a digital-voice look-alike must hold (s).
.br
Setting name \fBcontrol_seconds\fR, default \fB20 s\fR.
.br
Accepts: at least 1.
.RS
.PP
Only matters for P25, DMR and NXDN. On those systems the control channel and an ordinary digital conversation look identical for the first few seconds, and the only thing that tells them apart is that the conversation eventually pauses and the control channel never does. This is how long a signal has to keep going without a break before it is judged to be a control channel. Raise it if digital voice calls are being skipped by mistake; lower it if you are tired of waiting out control channels. It has no effect on the older Motorola and EDACS systems, which are recognised immediately from their symbol rate.
.RE
.TP
.B --lockout-control / --no-lockout-control
Lock out control channels \[em] add every control channel found to the lock-out list.
.br
Setting name \fBlockout_control\fR, default \fBno\fR.
.RS
.PP
Write each control channel into the lock-out list as it is found, so the scanner stops even looking at it. Skipping one already costs only a second or two, so this is worth turning on mainly if you scan the same band constantly and want the list built for you. With 'Remember lock-outs' also on, the entries are saved to your settings file and survive a restart.
.RE
.PP
.SS Receiver
.TP
.B -d --device
Device index \[em] which dongle to use when more than one is attached.
.br
Setting name \fBdevice_index\fR, default \fB0\fR.
.br
Accepts: at least 0.
.RS
.PP
Which receiver to use when more than one is plugged in. Run 'bandsaunter devices' to see the list and their numbers. With a single dongle this can be ignored.
.RE
.TP
.B --sample-rate
Sample rate \[em] capture rate; sets how much spectrum one step covers (Hz).
.br
Setting name \fBsample_rate\fR, default \fB2.048 MHz\fR.
.RS
.PP
How much spectrum the receiver takes in at once, which sets how much ground each step of the sweep covers. Higher covers the band in fewer steps but makes the computer work harder, and cheap dongles start dropping samples. 2.048 MS/s suits most machines; drop it if recordings sound wrong or the program warns about dropped samples.
.RE
.TP
.B -g --gain
Tuner gain \[em] gain in dB, or 'auto' for the tuner's own control (dB).
.br
Setting name \fBgain\fR, default \fBauto\fR.
.RS
.PP
How much the receiver amplifies. Automatic gain sounds convenient but tends to wind itself up during quiet moments and amplify noise until it breaks squelch. A fixed value is usually better for scanning: start around 30 and lower it if strong stations sound distorted, raise it if everything is too weak to hear.
.RE
.TP
.B --ppm
Frequency correction \[em] crystal error correction (ppm).
.br
Setting name \fBppm\fR, default \fB0 ppm\fR.
.RS
.PP
Cheap receivers are tuned by a crystal that is never exactly right, so every frequency reads slightly off, possibly by a few kilohertz at UHF. If stations consistently appear a little above or below where they should be, this corrects it. Leave at 0 unless you have measured the error.
.RE
.TP
.B --agc / --no-agc
RTL2832 AGC \[em] the demodulator chip's own automatic gain.
.br
Setting name \fBagc\fR, default \fBno\fR.
.RS
.PP
A second, separate automatic gain control inside the receiver chip, on top of the tuner gain. It is usually best left off, since two automatic gain controls fighting each other makes the squelch behave unpredictably.
.RE
.TP
.B --bias-tee / --no-bias-tee
Bias tee \[em] put DC on the antenna port to power an external amplifier.
.br
Setting name \fBbias_tee\fR, default \fBno\fR.
.RS
.PP
Sends power up the antenna cable, which is how mast-mounted amplifiers and some active antennas are fed. Leave it off unless you have such a device: switching it on with ordinary equipment attached can damage it.
.RE
.TP
.B --offset-tuning / --no-offset-tuning
Offset tuning \[em] shift the tuner's own local oscillator (E4000 tuners only).
.br
Setting name \fBoffset_tuning\fR, default \fBno\fR.
.RS
.PP
A trick for one older tuner chip, the E4000, that moves an artefact away from the middle of the picture. Modern dongles, including every R820T, ignore it. Leave it off unless you know you have that tuner.
.RE
.TP
.B --direct-sampling
Direct sampling \[em] HF reception below 24 MHz: auto, 0 off, 1 I branch, 2 Q branch.
.br
Setting name \fBdirect_sampling\fR, default \fBauto\fR.
.br
Accepts: one of: auto, 0, 1, 2.
.RS
.PP
How the receiver hears shortwave. These dongles cannot normally tune below about 24 MHz, but they can be persuaded to sample the antenna directly, which opens up everything beneath it: shortwave broadcast, amateur HF, marine. Automatic switches it on when you scan below 24 MHz and off again above. The Q branch is what almost all hardware uses.
.RE
.TP
.B --usable-fraction
Usable bandwidth \[em] fraction of the sample rate each step covers.
.br
Setting name \fBusable_fraction\fR, default \fB0.75\fR.
.br
Accepts: at least 0.1, at most 0.95.
.RS
.PP
The edges of what the receiver takes in are distorted by its own filtering, so only the middle portion is trusted. Lowering this uses less of each step and sweeps more slowly but avoids the poor edges; raising it covers ground faster at the cost of missing or mismeasuring signals near the edges.
.RE
.TP
.B --dc-guard
DC guard \[em] how far the local oscillator is parked below each step (Hz).
.br
Setting name \fBdc_guard_hz\fR, default \fB8 kHz\fR.
.br
Accepts: at least 0.
.RS
.PP
Every receiver of this type produces a spurious spike at the exact centre of where it is tuned, which would otherwise look like a station. The receiver is therefore deliberately parked slightly to one side. There is rarely a reason to change this.
.RE
.PP
.SS Output
.TP
.B -o --output
Output directory \[em] where recordings and logs are written.
.br
Setting name \fBoutput_dir\fR, default \fB~/bandsaunter\fR.
.RS
.PP
Where recordings, transcripts and logs are written. Everything the program produces goes here, so put it somewhere with room: audio adds up quickly, and raw IQ adds up very quickly.
.RE
.TP
.B --audio / --no-audio
Save audio \[em] write a WAV of the demodulated audio.
.br
Setting name \fBsave_audio\fR, default \fByes\fR.
.RS
.PP
Write the listenable audio file for each transmission. This is almost certainly what you want; turning it off leaves only the log and whatever other outputs are enabled, which is useful when you only care about what was active and when.
.RE
.TP
.B --iq --save-iq / --no-iq
Save raw IQ \[em] also write the raw complex samples and a SigMF sidecar.
.br
Setting name \fBsave_iq\fR, default \fBno\fR.
.RS
.PP
Also keep the raw radio samples, exactly as they came off the receiver, alongside the audio. These can be re-analysed or decoded later with other software, but they are enormous, many megabytes per second, so leave this off unless you have a specific use for them.
.RE
.TP
.B --iq-format
IQ format \[em] sample format for raw IQ files.
.br
Setting name \fBiq_format\fR, default \fBcf32\fR.
.br
Accepts: one of: cf32, cs16.
.RS
.PP
The number format for those raw files. cf32 is the easiest for other programs to read; cs16 is half the size for the same samples. Only matters if raw IQ is being saved.
.RE
.TP
.B --audio-rate
Audio rate \[em] preferred audio sample rate (Hz).
.br
Setting name \fBaudio_rate\fR, default \fB16 kHz\fR.
.br
Accepts: at least 4000.
.RS
.PP
The sample rate of the saved audio. Higher preserves more of the original sound at the cost of file size; the default is well matched to what a radio channel can actually carry, and to what speech recognisers expect.
.RE
.TP
.B --classify / --no-classify
Identify signals \[em] work out what kind of signal each capture is.
.br
Setting name \fBclassify\fR, default \fByes\fR.
.RS
.PP
Work out what each recording actually is, whether FM voice, AM, single sideband, Morse, a paging system or a digital voice mode, and write it into the log and the filename. Turning it off saves a little processing and leaves you to identify things by ear.
.RE
.TP
.B --morse / --no-morse
Decode CW to text \[em] decode keyed carriers as Morse.
.br
Setting name \fBdecode_morse\fR, default \fByes\fR.
.RS
.PP
Turn keyed carriers into readable text, with the sending speed. Morse is still in daily use by amateurs and by beacons, and this saves you learning to read it by ear. It costs almost nothing when there is no Morse about.
.RE
.TP
.B --log-file
Log file \[em] name of the run log inside the output directory.
.br
Setting name \fBlog_file\fR, default \fBscan_log.jsonl\fR.
.RS
.PP
The name of the run log inside the output directory. It records every recording with its time, frequency, duration and identification, as JSON lines with a spreadsheet-friendly .csv alongside.
.RE
.PP
.SS Combining
.TP
.B --combine / --no-combine
Combine by frequency \[em] collect every transmission on one frequency into a single file.
.br
Setting name \fBcombine_by_frequency\fR, default \fBno\fR.
.RS
.PP
Instead of one file per transmission, keep one growing file per frequency, with each new transmission appended to it. This turns a scanner run into something you can play like a recording of that channel, rather than hundreds of fragments to click through.
.RE
.TP
.B --announce / --no-announce
Speak the time \[em] insert a spoken date and time before each transmission.
.br
Setting name \fBannounce_timestamps\fR, default \fByes\fR.
.RS
.PP
Speaks the date and time before each transmission in a combined file, so you can hear when something happened without watching a clock or reading filenames. It works with no extra software installed; installing espeak-ng makes the voice clearer.
.RE
.TP
.B --announce-frequency / --no-announce-frequency
Speak the frequency \[em] also read the frequency out with the timestamp.
.br
Setting name \fBannounce_frequency\fR, default \fBno\fR.
.RS
.PP
Also read out the frequency with the time. Useful when several nearby frequencies end up in the same combined file, or when you want a spoken record of what you were listening to.
.RE
.TP
.B --announce-engine
Speech engine \[em] which text-to-speech to use: auto, builtin, or a program name.
.br
Setting name \fBannounce_engine\fR, default \fBauto\fR.
.RS
.PP
Which voice does the speaking. Automatic uses the best available: espeak-ng if it is installed, otherwise a small built-in synthesiser that needs nothing at all. Set it to builtin to force the internal voice, or name another program.
.RE
.TP
.B --combine-tolerance
Same-frequency tolerance \[em] how far apart two receptions may be and still count as one frequency (Hz).
.br
Setting name \fBcombine_tolerance_hz\fR, default \fB6.25 kHz\fR.
.br
Accepts: at least 0.
.RS
.PP
How far apart two receptions may be and still be treated as the same frequency for combining. Transmitters drift and the measurement is never exact, so a little tolerance keeps one repeater in one file. Widen it if a single channel is being split across several files.
.RE
.TP
.B --keep-individual / --no-keep-individual
Keep separate files too \[em] also keep the one-file-per-transmission recordings.
.br
Setting name \fBcombine_keep_individual\fR, default \fBno\fR.
.RS
.PP
Keep the per-transmission files as well as the combined one. It costs twice the disk space, but means you can still pick out a single transmission without seeking through a long file.
.RE
.PP
.SS Transcription
.TP
.B --transcribe / --no-transcribe
Transcribe speech \[em] write out what was said in each voice transmission.
.br
Setting name \fBtranscribe\fR, default \fBno\fR.
.RS
.PP
Write out what was said in each voice transmission as a text file beside the recording, so a scan can be read rather than listened to, and searched with ordinary text tools. It needs a speech recogniser installed; the program says so plainly if none is present.
.RE
.TP
.B --transcribe-engine
Recogniser \[em] which speech recogniser to use, or auto.
.br
Setting name \fBtranscribe_engine\fR, default \fBauto\fR.
.RS
.PP
Which speech recogniser to use when more than one is installed. Automatic picks the best available. Radio audio is hard for these programs, and the whisper-based ones are noticeably better at it than the smaller alternatives.
.RE
.TP
.B --transcribe-model
Model \[em] model the recogniser should load.
.br
Setting name \fBtranscribe_model\fR, default \fBbase.en\fR.
.RS
.PP
How large a recognition model to load. Bigger models are more accurate and slower, and take more memory: tiny.en and base.en keep up comfortably on an ordinary machine, small.en and medium.en are better but heavier.
.RE
.TP
.B --transcribe-language
Language \[em] language to expect, or blank to detect it.
.br
Setting name \fBtranscribe_language\fR, default \fBen\fR.
.RS
.PP
The language to expect. Setting it is worth the trouble: on a short, noisy clip automatic detection often guesses wrong and returns confident nonsense in a language nobody was speaking. Leave it blank only if you genuinely do not know.
.RE
.TP
.B --transcribe-min
Skip clips shorter than \[em] do not bother transcribing very short captures (s).
.br
Setting name \fBtranscribe_min_seconds\fR, default \fB1 s\fR.
.br
Accepts: at least 0.
.RS
.PP
Do not bother transcribing captures shorter than this. Very short clips rarely contain a whole word and mostly produce noise or nothing, while still costing the processing.
.RE
.PP
.SS Run control
.TP
.B --cycles
Stop after sweeps \[em] stop after this many full passes (0 = run until stopped).
.br
Setting name \fBmax_cycles\fR, default \fBno limit\fR.
.br
Accepts: at least 0.
.RS
.PP
Stop after this many complete passes through all the frequencies. Useful for a quick survey of what is active, or for a scripted run that must finish. 0 means keep going until you stop it.
.RE
.TP
.B --duration
Stop after time \[em] stop after this long (0 = run until stopped) (s).
.br
Setting name \fBmax_runtime_seconds\fR, default \fBno limit\fR.
.br
Accepts: at least 0.
.RS
.PP
Stop after this long, whatever the scan is doing. Handy for an unattended run, or for keeping a test short. 0 means no limit.
.RE
.TP
.B --lockout
Locked-out frequencies \[em] never stop on these frequencies.
.br
Setting name \fBlockout\fR, default \fB(none)\fR.
.RS
.PP
Frequencies the scan must never stop on. Every receiving setup has a few: a pager transmitter down the road, a nearby data link, or a spurious signal the receiver manufactures itself. Give several separated by commas, and a whole stretch of spectrum as a pair, such as 162.55M, 450M-455M.
.RE
.TP
.B --lockout-width
Lock-out width \[em] how wide a locked-out frequency is (Hz).
.br
Setting name \fBlockout_width\fR, default \fB12.5 kHz\fR.
.br
Accepts: at least 1.
.RS
.PP
How wide a single locked-out frequency is. A transmitter is never exactly on its nominal frequency, so the block covers a little either side. A lock-out written as a span ignores this and uses exactly the width you gave.
.RE
.TP
.B --quiet / --no-quiet
Quiet output \[em] print errors only.
.br
Setting name \fBquiet\fR, default \fBno\fR.
.RS
.PP
Print only errors. For running from a script or a scheduled job where the usual progress reporting would just fill a log file.
.RE
.TP
.B --save-lockouts / --no-save-lockouts
Remember lock-outs \[em] keep frequencies locked out during a scan.
.br
Setting name \fBsave_lockouts\fR, default \fByes\fR.
.RS
.PP
When you lock a frequency out during a scan, remember it for later runs instead of only the current one. Only the lock-out list is written back, so options you passed for one run stay one-off. Turn it off if you would rather the program never modified your settings file.
.RE
.TP
.B --plain / --no-plain
Plain display \[em] print one line per hit instead of the live display.
.br
Setting name \fBplain\fR, default \fBno\fR.
.RS
.PP
Print one line per recording instead of the live updating display. The live display needs a real terminal; plain output is what you want over a remote connection, when saving output to a file, or when feeding another program. It is chosen automatically when output is not going to a terminal.
.RE
.PP
.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.
.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 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.
.PP
.BR saunterbrowse (1)
reads these back, and lists any callsigns it finds in them with the licence
they belong to.
.SH HF RECEPTION
These receivers cannot normally tune below about 24 MHz. Below that they can
sample the antenna directly instead, which opens up shortwave: broadcast,
amateur HF, marine, aviation. It is switched on automatically when a scan
goes below 24 MHz. A direct connection to a suitable antenna is needed; the
whip supplied with most dongles will hear very little.
.SH SINGLE SIDEBAND
Single sideband is the one mode where tuning must be exact: its demodulator
is a filter that opens at the suppressed carrier, so tuning to the middle of
the voice discards its lower half and shifts the rest. bandsaunter measures
where the carrier is rather than assuming, and identifies upper from lower
sideband by which way the signal's energy leans, so
.B \-\-mode usb
is not needed. The frequency in the filename is the carrier \[em] the
frequency to dial into a radio.
.SH FILES
.TP
.I ~/.config/bandsaunter/config.yaml
The settings every run starts from.
.TP
.I ~/.config/bandsaunter/*.yaml
Named profiles.
.TP
.I ~/bandsaunter/
Where recordings, transcripts and logs are written, unless
.B \-\-output
says otherwise. Chosen on first run.
.TP
.I /etc/modprobe.d/blacklist-rtlsdr.conf
Written by the package to keep the DVB-T television driver from claiming the
receiver.
.SH ENVIRONMENT
.TP
.B BANDSAUNTER_CONFIG_DIR
Where settings and profiles live, instead of
.IR ~/.config/bandsaunter .
.TP
.B BANDSAUNTER_LIBRTLSDR
Path to a particular librtlsdr shared library, when the system one is not the
one wanted.
.TP
.B BANDSAUNTER_DRIVER_MESSAGES
Set to 1 to let the receiver driver print its own chatter, which is
suppressed by default because it draws over the live display.
.TP
.B BANDSAUNTER_VENDOR_DIR
Where a packaged speech recogniser is installed. Default
.IR /usr/lib/bandsaunter/vendor .
.TP
.B BANDSAUNTER_MODEL_DIR
Where packaged recognition models are installed. Default
.IR /usr/share/bandsaunter/models .
.TP
.B BANDSAUNTER_ENGINE_OUTPUT
Set to 1 to let the speech recogniser print its own progress.
.SH EXAMPLES
.TP
.B bandsaunter
Interactive menus: pick bands, change settings, start scanning.
.TP
.B bandsaunter scan \-b 2m \-b 70cm \-\-record 0 \-\-hang 6
Scan two amateur bands, following each conversation to its end and allowing
six seconds of silence between overs.
.TP
.B bandsaunter scan \-b marine\-vhf \-\-combine \-\-transcribe
Scan marine VHF, keeping one growing file per channel with spoken timestamps,
and write out what was said.
.TP
.B bandsaunter scan \-r 14.0M\-14.35M
Scan the 20 metre amateur band. Direct sampling switches on by itself.
.TP
.B bandsaunter scan \-b all\-cw \-\-decode\-morse
Sweep every Morse segment of every amateur band and decode what is heard.
.TP
.B bandsaunter scan \-b gmrs \-\-plain \-\-duration 3600
Scan GMRS for an hour with line-per-hit output, suitable for a log file or a
remote session.
.TP
.B bandsaunter config threshold_db=12
Raise the squelch threshold and save it as the new default.
.SH EXIT STATUS
0 on success, 1 for a bad option or an unusable configuration, 2 when the
receiver could not be opened.
.SH SEE ALSO
.BR saunterbrowse (1)
\[em] browse and play back what a scan collected: the recordings list, their
transcripts and their identifications, on one screen.
.PP
.BR rtl_test (1),
.BR rtl_sdr (1),
.BR espeak-ng (1)
.PP
The README shipped with the package covers the same ground at greater length,
including why the detection thresholds are what they are.
.SH BUGS
The DVB-T television driver claims these dongles on sight. If the receiver
cannot be opened, that is almost always why: the package blacklists the
driver on install, but the module must be unloaded once with
.B "rmmod dvb_usb_rtl28xxu"
or the dongle replugged.