Four things the ADS-B mode was missing, and one it was actively getting
wrong.
The band plan lists 1090 MHz because that is where ADS-B is, so choosing
it from the band plan is the obvious thing to do -- and it records the
bursts as clicks in a WAV file and decodes nothing, silently. Both the
scanner and the menus now say so, before the sweep starts, and name the
mode that does decode it. It is not refused: looking at the raw spectrum
is a fair thing to want.
Menu 5, Aircraft (ADS-B), is the whole mode without a command line. Every
option on one screen with a line saying what it does, ?N for the long
version and the flag it corresponds to, l to listen, m to draw a map from
any log, s to keep the options. The listening and the drawing moved into
bandsaunter/aircraft.py so the menus and the command line run the same
code.
While it listens the screen is a live board: one line per aircraft in the
order first heard, the counter climbing as frames arrive, height coloured
low warm to high cold with an arrow for climb or descent, the age of the
last report going green to red, and the line removed once nothing has been
heard for --hold seconds, everything below moving up. The registers are
asked while it runs, so registration, type, operator and route fill
themselves in as the answers arrive.
--speed-unit knots|mph|kph changes the heading of that board, the speed
beside every aircraft on the map and the speeds in the report, and moves
the distances with it so that one picture never carries two different
miles. The log stays in knots, which is what the aircraft broadcast.
And there is a real map under the flight paths: {z}/{x}/{y} tiles fetched
once, cached in ~/.cache/bandsaunter/tiles, reprojected from Web Mercator
pixel by pixel, inverted and dimmed so the aircraft stay the brightest
thing on the picture. The PNGs are decoded here -- zlib and the five row
filters from the specification, checked byte for byte against Pillow on
real tiles -- so nothing new is depended on. Tiles are cached and never
re-fetched, every request says who is asking, and the attribution is drawn
onto the picture, because a GIF travels without its readme.
conftest now fails any test that reaches for a tile server or a register.
It caught four of these on the way in.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016PsWPTweCT6pwxKngvVxcg
The program had no licence file at all, and pyproject claimed MIT into
the void. It is now the GNU General Public License, version 3 or later:
LICENSE holds the text verbatim, pyproject declares it with the OSI
classifier, both .deb builds write /usr/share/doc/<pkg>/copyright in the
machine-readable format Policy requires, both manuals carry a COPYING
section, and --version prints the GNU notice on both programs.
INSTALL.md is the step-by-step: what you need, the Debian package, the
virtual environment for everywhere else, how to check it worked, every
optional dependency with what it buys and what happens without it, and
the errors people actually hit first -- PEP 668 at the top, because on
Debian a plain "pip install ." refuses and reads as a broken program.
Speech transcription gets its own four steps, because it is the only
part with a real download in it: the recogniser into the environment
bandsaunter runs from, checking it took, the model (base.en, 148 MB,
from Hugging Face into ~/.cache/huggingface, fetched deliberately rather
than in the middle of a scan), then turning it on. With the sizes of
every model, the offline routes, and what to do when --engines says no
although pip says yes.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016PsWPTweCT6pwxKngvVxcg
ADS-B was a live table and nothing else: an aircraft was overhead for four
minutes and then gone, with nothing kept. Now everything heard goes into
adsb_<time>.jsonl as it arrives -- one object per frame, the raw hex beside
what was read out of it, flushed per line because a listening session ends
with control-C -- with a readable report beside it.
flights.py asks who the aircraft are: adsbdb for the airframe and the
route, hexdb behind it, cached for a month. What needs no website is
answered without one, because the ICAO address block says which country
registered the aircraft and the first three letters of an airline callsign
are its designator. Nothing but the address and the callsign heard on the
air is ever sent.
bandsaunter flights [LOG...] --out sky.gif
reads a log back and draws the evening as a map with the clock running.
Every frame is a moment: each aircraft is where it actually was then,
interpolated between the position reports either side of it and
dead-reckoned from its last speed and heading between them, and dropped
rather than guessed at once it has not been heard for --stale seconds.
The GIF is written here -- palette, LZW, frame differencing against a
transparent index -- so nothing but numpy is needed; ffmpeg writes an MP4
where it happens to be installed, and .png draws the whole evening at once.
The decoder needed 6.3 s to read a second of sky, so a live capture was
losing six frames in seven. Reading the bits off a running total instead
of summing each window takes that to 0.6 s, with identical output.
--simulate flies six aircraft that are not there past a receiver that is
not there, through the real encoder, the real checksum and the real
decoder, so all of this can be tried without an aerial.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016PsWPTweCT6pwxKngvVxcg
A repeater identifying itself in CW over an FM carrier came back from the
recogniser as "2-2-2-3-3-5-2-7-0-5-9-7-0-8-1-0" -- one digit per tone,
sixteen characters of nothing, which cleared the five-character bar and
cost the capture its waterfall.
The rule now lives in one place, waterfall.is_readable, shared by the
scanner and the waterfall command: voice, no Morse, and more than a
handful of characters.
bandsaunter waterfall --check-morse
runs the CW decoder over the recordings a sidecar calls readable, for
sidecars written before the decoder could hear an ident over an FM
carrier, and draws -- and records the ident in -- the ones that have one.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016PsWPTweCT6pwxKngvVxcg
Every capture that is not voice, or whose voice yields five characters
or fewer of transcript, now gets a PNG of the waterfall it would have
painted on screen: spectrogram from the IQ where it was kept, from the
demodulated audio otherwise, captioned and labelled either way.
The browser shows it in the picture panel, but only when there is no
transcript, Morse or decoded data to show instead.
bandsaunter waterfall [PATH...] [--all] [--redraw] [--min-chars N]
draws them after the fact for recordings already on disk.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016PsWPTweCT6pwxKngvVxcg
A base station identifying itself in CW does not key its carrier. 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. On the land-mobile bands that is nearly all the Morse there is,
and none of it was being read: an ident of KSQ330 sat in the middle of
a 27-second capture on 154.369 MHz, cleanly keyed at 22 WPM, and the
capture was filed as voice with no Morse in it at all.
Three things were in the way, and each was found by measuring rather
than by reading.
The whole-recording decode ran only for captures recorded in cw mode.
An ident over FM is recorded in nfm, so it was never looked for. It
now runs for every capture.
The tone was sought in the first four seconds of the audio and nowhere
else, so a tone that had not started yet could not be found -- on the
capture above it locked onto the harmonic of something else. It is now
averaged over the whole clip.
And the steady tone either side of the ident was read as a character
the window had sliced, which dropped the first and last letter and,
through complete_text, the whole callsign: one word with no gap in it
to survive the drop. A mark far longer than any dash is not a
truncated element, it is the transmission the ident was sent over.
Even fixed, the decoder measures its tone and its key-down threshold
over the whole of whatever it is handed, so a half-minute recording
with five seconds of keying in the middle measures both from the other
twenty-five. So the audio is searched a few seconds at a time, plus
the whole capture -- that one matters for a beacon keying throughout,
where the longest window is the best one and leaving it out lost an
ident the decoder had always read.
Nothing was loosened. Every window is judged by is_morse exactly as a
whole capture is. Across 677 real captures the search claimed Morse in
four: KSQ330 and WNRS309, both FCC land-mobile callsigns and neither
seen before; a 20 WPM burst on 70 cm reading as E7HNN, plausible and
unverified; and noise on 445.5 MHz reading as "T T T E E E E E E E E".
That last one is the new rule -- E and T are the one-element
characters, so a decode of nothing but those can hardly be wrong,
because there is nothing in it to get wrong. With it the count is
three.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016PsWPTweCT6pwxKngvVxcg
Two things, both found by measuring rather than by reading the code.
The voice-activity filter inside the recogniser is off. It was costing
words: across a night of land-mobile captures it dropped 5-15% of what
the same model finds without it -- 491 against 507, 339 against 384,
263 against 310 -- because a single-word over between two
transmissions looks to a VAD exactly like the noise it exists to
remove, and on a scanner those short replies are the ones worth
having.
Turning it off has a cost, and the cost is that Whisper hands back
"You" for five seconds of hiss as confidently as it hands back a
sentence. So the whole capture is now asked once whether anything in
it rises above its own noise. Digital silence measures 0.0 dB of
contrast and hiss at any level 0.7, while the quietest real capture of
that night measures 8.9 and most measure 10-27; the bar sits at 3, an
order of magnitude clear of both. It can veto a capture but never trim
one, which is the whole difference between it and the filter it
replaces.
The second thing: callsigns like WQVF960 were being missed entirely.
The shape being matched was the amateur one -- prefix, district digit,
suffix -- and everything else the FCC licenses is written the other
way round, the letters first and then the digits. On the GMRS and
business channels that is most of what is said: nine callsigns across
five transcripts of one evening went by unrecognised, and now do not.
The shape is written as the three allocations that exist rather than
as "letters then digits", which claims KN95, WD40 and KC135. Its
letters are checked against the word list even when they arrive as a
single token, which the amateur shape does not need -- no English word
has a digit in the middle of it, but "west 120" and "word 100" fit
this one exactly.
Lookups now fall back to hamdb.org when callook has nothing. Not a
spare copy: callook holds United States amateur licences only, so
DL1ABC and VE3ABC are INVALID there and resolve perfectly well from
the other. And a GMRS callsign is not looked up at all -- every
database reachable without an account is an amateur register, so
reporting WQVF960 as "unlisted" would blame the callsign for the
absence of a source.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016PsWPTweCT6pwxKngvVxcg
The listing gave the time and not the date, which is fine for an
evening's scanning and useless for a directory that has been filling
for a fortnight: two recordings a week apart looked like neighbours.
Every moment in the browser is now written YY-mm-dd hh:mm:ss am/pm --
date first so a column of them reads down in order, twelve-hour so it
reads the way it would be said. Midnight is 12 am and noon is 12 pm,
which is the pair a twelve-hour clock gets wrong when it is done by
subtraction, so both are tested.
The sort is named "date/time" rather than "time" and orders by the
whole moment, with the filename breaking a tie so that the list does
not shuffle itself between one reload and the next. --sort time still
works; it is the sort of thing that lives in a shell alias.
The date costs twelve columns, so the frequency column is now only as
wide as the widest frequency in the list rather than always wide
enough for 1090.000001 MHz. It is fixed for the whole list, not the
screenful, because a column that resizes as the list scrolls under it
makes the whole listing appear to twitch.
--list is left in ISO and twenty-four hours: it is there to be piped
into grep and sort, and those want the format that sorts as text.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016PsWPTweCT6pwxKngvVxcg
Hexadecimal is a true answer to "what did that say" and not a useful one.
This is the work of turning the rest of what a receiver hears into
something a person can read, and most of it is pictures.
PICTURES
Three of the things on the air are images rather than sounds, and all three
arrive as the audio a scan already records:
SSTV 14.230 and 144.5 MHz Martin M1/M2, Scottie S1/S2/DX, Robot 36/72
APT 137-138 MHz the NOAA weather satellites
HF fax 2-20 MHz, sideband the marine weather charts
Each is written from its published specification, and the generators used to
test them are written from the same specification without reference to the
decoders -- so a picture that comes back matching the one that went in is
evidence about the format. Every SSTV mode reproduces its published line
time exactly, which is worth failing a test over: a line a few milliseconds
long walks the picture off the screen inside ten lines. Against synthetic
transmissions at 30 dB SNR, SSTV is 96-98% of pixels exact, APT correlates
at 0.97 and fax at 0.998; all three still read at 6-12 dB.
None of the three is guessed at, and that is what makes it safe to try them
on every recording. SSTV needs its VIS header, APT needs both line syncs at
the right distance from each other, fax needs the phasing signal. No false
pictures in 295 attempts over noise, tones, speech and swept whistles.
Two things had to be got right beyond the arithmetic. A band-pass does not
switch between two tones, it slides between them, so every edge is measured
at the midpoint of the slide rather than at the first sample past a
threshold -- the earlier version was reading the coarse search stride back
as the edge and shifting Martin M1 sideways by a whole colour bar. And a
picture now keeps its capture whatever the content check made of it: a
satellite is a steady tone with a wobble on it and SSTV is a whistle, so
both were being discarded as "no signal content" having already been
recognised.
PNG is written here rather than pulled in from Pillow. A scanner that
cannot start because an imaging library is missing is worse than one that
cannot draw.
saunterbrowse marks a picture in the list, gives its path in full -- wrapped
rather than cut off, because half a path opens nothing -- and moves or
deletes the PNGs with the recording. o prints the picture's path, not the
audio's.
GRIB is not a modulation and is not pretended to be one. It is the format
weather models are published in and it travels by satellite link and by
e-mail; where a decoded byte stream begins with its magic number it is
named, and that is all.
AIRCRAFT
`bandsaunter adsb` parks the receiver on 1090 MHz and reads Mode S extended
squitter: address, callsign, altitude, position, speed. A command of its
own because a megabit a second will not go through a channel twelve and a
half kilohertz wide. Every frame carries a 24-bit checksum so there is no
threshold anywhere in it -- with one trap, which is that a frame of all
zeros satisfies that checksum and silence is exactly that. Positions round
trip exactly through compact position reporting, and a pair straddling a
longitude-zone boundary is refused rather than resolved against two grids.
METERS AND SENSORS
Itron ERT utility meters on 900 MHz and AcuRite weather sensors on 433 MHz
are named rather than reported as hex, and neither is believed without its
own checksum -- BCH(255,239) for the meter, a checksum and four parity bits
for the sensor. Both are implemented from published descriptions and
checked against frames built from the same descriptions, which proves the
framing and the arithmetic and is not the same as having held a meter.
HEX INTO WORDS
Everything else that decodes to bits now gets its fields named where the
shape is standard, its text read out where there is text, and its bytes laid
out in groups with the printable characters beside them.
The text search is where the care went, because printability is not
evidence. Forty framings of each packet, and seven-bit values printable
three in four, meant a bar set on printability called 64% of random payloads
text. Real text is nearly all one case where random letters are half and
half, two fifths vowels where random is a fifth, and mostly alphanumeric
where random draws punctuation one time in four. Together: under 0.5%,
measured in the suite.
CALLSIGNS
The licensed address is recorded in full -- the street, not merely the town
-- and goes into the KML with everything else. US amateur records are
public by law and carry it; holding it and not saying so is worse than
either showing it or not asking, and --no-lookup asks for none of it.
Also here: Morse is decoded again from the whole recording where the capture
was made in cw mode. The first pass works from the classifier's buffer,
which holds a few seconds -- enough to say "this is Morse", not enough to
catch a callsign whole between two word gaps, so a beacon repeating every
eight seconds through an eight-second window was never identified.
And classify._psk_order took the logarithm of zero on a silent block.
1318 tests, up from 1161.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016PsWPTweCT6pwxKngvVxcg
Most of what identifies itself on the air identifies itself in Morse. A
repeater, a beacon, an unattended transmitter: four to six characters, over
in a second or two, and no speech anywhere in the capture. Every one of
those was being thrown away, in three separate places.
The callsign book and the map were built inside the transcription branch,
on the reasoning that callsigns come out of transcripts. They also come out
of Morse and out of APRS headers, neither of which involves a speech
recogniser -- so a receiver with none installed found none of them, and a CW
ident reached the sidecar and stopped there. Both are now built whenever
classification is on, and all three sources go through one place.
The CW decoder only ran where the classifier had already said cw, ook or
carrier. A two-second ident is a fraction of a capture named after whatever
filled the rest of it. Every capture is offered to it now, once it has
finished; a decode does not relabel a capture that plainly holds speech.
And the decoder's own gates were written for a paragraph. Three characters,
eight elements, and any repeated character refused -- which read VVV, DE, AR
and K correctly and then discarded them. Short is the normal case now, on a
second bar: perfect timing, nothing undecoded, and the keyed tone at least
20 dB over its band. That last is not decoration. With four elements the
dot length is fitted to those very elements, so noise lands on the grid as
neatly as keying does; a third of a second of white noise decodes as a
perfectly timed V. Over 200 noise blocks the loudest bin never rose 13 dB
above the median while keying at 3 dB SNR sits above 40. One keyed element
is still refused: a single pulse is an E or a T whether a person sent it or
the squelch opened on a click. 288 non-Morse cases, no false positives.
Feeding that text to a callsign lookup made truncation matter. A capture
opens when the squelch does, halfway through an element as often as not, and
half a character is not a smaller reading -- a K missing its first dash is
an A. So the sliced character is dropped, and so is the rest of its word,
because what is left can read as a whole one: K1AA caught halfway through is
K1A, which is somebody else. Across 1805 truncated captures that is 107
invented callsigns down to none, with 550 correct ones still found.
Phonetics, which is the other half of the ask. A recogniser has never heard
of the alphabet -- it writes what the words sounded like:
Whiskey-One-Alpha-Whiskey hyphenated
WhiskeyOneAlphaWhiskey run together
Whiskey1AlphaWhiskey and half in digits
wiskey one alfa whisky spelled the way it sounded
whiskey one alpha, uh, whiskey with the hesitation written down
All read back to W1AW now. A word is only taken apart when it is phonetic
all the way through, which is what keeps it off "kilometre" and "victorious".
Two bugs found on the way, both of which invented a callsign:
- Nothing is joined across a slash any more. The beacon W1AW/B came back
as W1AWB, which belongs to nobody, and W1AW-4 came back as nothing at all.
- Nor across a gap the sender chose. A transcript's spacing is the
recogniser's guess and may be closed up; a word gap in Morse is seven dot
units, so "KU0W K" is a station signing off, not a longer callsign.
Also here:
- saunterbrowse gives Morse a panel of its own, with the licence under it,
searchable with / and readable with t.
- --simulate no longer looks anything up or writes a map. The demo band is
invented but W1AW is the ARRL's own station, and it would have been
pinned to the same map a real scan writes.
- classify._psk_order took the logarithm of zero on a silent block.
- The demo band has a repeater ident in it, and its Morse no longer runs
one repeat into the next.
- conftest refuses a real licence lookup from any test.
1161 tests, up from 1014.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016PsWPTweCT6pwxKngvVxcg
A night's scan leaves hundreds of files, most worth nothing and a few of
them the reason it was left running. Sorting that out meant leaving the
browser and going at the directory with mv and rm.
Five keys, meant to be pressed once each going down the list:
S I N file it into saved/, investigate/ or noise/
u put the last one filed back
d delete it and its sidecars, for good -- asks first
m lock the frequency out, so no later scan stops on it
Each of these acts on the whole capture -- the .wav, the JSON sidecar, the
IQ, the transcript and the decoded data -- because a recording in one
directory and its transcript in another is a pair nothing will ever put
back together. A move that cannot be finished puts back whatever already
moved. The cursor stays on the row it was on, which is now the next
recording, since a cursor that jumped would make one-key-per-recording
impossible.
m writes to the lock-out list in the settings file, the same one the
scanner's own l key maintains, so a birdie found while reading last night's
recordings is gone from tonight's. It says "the next scan": one already
running read its settings when it started.
The subdirectories sit under the recordings directory, so a scan writing
there never looks in them, and saunterbrowse ~/bandsaunter/saved reads one
back.
Also here, because this is the first part of the browser that writes:
- The help screen is back inside eighty by twenty-four. It had grown past
the bottom of an ordinary window, which puts "q quit" off the screen.
- The footer drops keys in a deliberate order when the window is narrow,
rather than ellipsising whichever happened to be at the end.
- Moving or deleting what is playing stops the player first.
- The pty harness accepted an env and ignored it, so a test aimed at a
throwaway settings directory wrote to the real one. It honours it now,
and conftest redirects the settings directory for every test besides.
1014 tests.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016PsWPTweCT6pwxKngvVxcg
Resizing the terminal during a scan left the screen full of wreckage:
box corners in the middle of a line, borders twice the width of the
window, a "receiver" header printed eight times down the left edge. Four
separate defects, which is why it looked so bad.
Live rendering works by moving the cursor back over the frame it drew
last time and overwriting it. That is only correct while the frame is
still where it was put, and none of these programs noticed when it was
not.
1. Nothing detected a resize. Both the scan display and saunterbrowse
now compare the console size on every frame and clear the screen when
it changes -- polled rather than handled as a signal, because the
display is redrawn several times a second anyway and a signal handler
that runs in the middle of a write has to be right about far more than
this does. Anything printed before the scan started scrolls away at
that point, which the manual now says.
2. The layout's model of its own height was wrong, in two places that
cancelled. The sweep panel was counted as one line shorter than it
is, the hit list as one line taller. The sum came out right whenever
both were drawn and wrong on a terminal too short for the hit list --
where the frame then overflowed by one line on every refresh and the
top of it marched down the screen. That is what the eight headers
were. Each panel height is a named constant now, and a test checks
every one of them against what is actually rendered.
3. Lines inside the panels could wrap. A band name, a long status line
or a decoded message made a panel a row taller than the arithmetic
allowed for, with the same result. Every one is drawn on a single
line and ellipsised now. The receiver panel drops its optional parts
instead, keeping the tuner and the flags: "SIMULATED" disappearing off
the end of a narrow line is how somebody comes to believe they are
listening to the air.
4. saunterbrowse's full-screen views did not fill the screen. Nothing
erases the alternate screen between frames -- the cursor is sent home
and the new frame written over the old one -- so pressing t or ? on a
tall window left most of the recording list visible underneath. Both
are wrapped in a layout now, which fills the terminal exactly.
The layout also gives up the receiver panel on a very short terminal,
which it previously had no way to do: on eight rows the smallest frame it
could describe was nine lines.
Testing this by rendering to a wide Console and reading the text back
cannot work -- whether the cursor lands where it should is a property of
the terminal, not of the renderable. So tests/terminal.py runs the
program in a pty, resizes the window underneath it the way a window
manager does, and feeds what it writes to a terminal emulator whose
screen is then read. Every fix above has a test that fails without it,
checked by reverting each one in turn. pyte is a dev dependency and
those tests skip without it; the arithmetic ones need nothing.
Also: t now opens the reader for a capture that carries decoded data
rather than speech, because the decoded panel already told the reader to
press it.
869 -> 949 tests.
Much of what a scanner finds is not speech. Doorbells, tyre-pressure
sensors, weather stations, remote controls, paging and packet radio all
carry something a receiver can read, and until now the answer was "OOK /
ASK data burst" and a WAV file. Now the bits come out.
The observation the whole thing is built on is that whatever the
modulation, a data signal is the same shape once it has been sliced: a
train of alternating runs whose lengths carry the information. On-off
keying gives that directly -- the carrier is up or it is down -- and
two-level FSK gives exactly the same thing from the discriminator, one
tone or the other. So both reduce to a run-length train and everything
after that is shared.
What the runs mean is the line code, and it is worked out from the runs
alone rather than configured, because each code makes a different
prediction about which of the two histograms is the bimodal one: PWM
(EV1527, PT2262, and nearly every 433 MHz remote), PPM, Manchester, and
plain NRZ. Four-level FSK is recognised as such and read as symbols
rather than sliced down the middle, which produces bits that mean
nothing; where a frame sync word appears the system is named outright.
Two protocols carry their own framing and checksums and so are read in
full. POCSAG paging: all three rates tried because nothing in the signal
says which it is, every codeword checked and single-bit errors corrected
against the BCH code, and the address, function letter and message text
reported. AX.25 as APRS uses it: the frame check has to come out right
before a frame is reported at all, and the sender's callsign goes onto
the map with everyone else's.
The hard half is refusing what is not data. Noise sliced at a threshold
produces runs and runs produce bits, so three things guard against it:
the runs have to quantise to the line code's own grid; most of the bursts
in a capture have to decode the same way, because one lucky window in
eight is a coincidence and that is exactly what SSB voice produced; and,
much the strongest, the packet has to repeat, because bits that come back
identical six times did not come from noise. A reading with none of that
behind it is reported as nothing at all rather than as a bit string with
a low number beside it that somebody will read anyway. Across 27
recordings of speech, music, static, a bare carrier, Morse and PSK it
returns nothing 27 times.
A firm decode also outranks the content check, which is statistical: 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. Such a capture is kept and filed as data, not as voice.
What comes out is written to a _data.txt beside the recording, shown on
the live display and in the line-per-hit output, and takes the place of
the transcript at the top of saunterbrowse -- where it is searchable, so
"which page mentioned engine 4" is a question that can be asked.
`bandsaunter analyze` decodes a file you already have.
The simulator gained two honest transmitters to test against: a
pulse-width remote that repeats a real payload, and a pager that sends
real POCSAG batches with real BCH check bits. Random keying exercises
the classifier but leaves a decoder nothing to get right. The POCSAG
encoder lives next to the decoder rather than in the test helpers, so a
bug shared by both cannot hide.
Fixed along the way:
- Rich reads a square bracket as markup, and a decoded page is arbitrary
text off the air. "[/x]" in a message ended the live display with a
MarkupError; so did typing "[/" at saunterbrowse's search prompt.
Everything that did not come from this program is escaped now.
- Otsu returned the first bin of a plateau. Two populations with nothing
between them -- silence and full carrier, which is what on-off keying
is -- make every threshold in the gap equally good, and taking the
first put it hard against the lower population with the hysteresis band
outside the data entirely, so nothing sliced at all.
- Estimating the symbol clock by counting along a cumulative grid is a
fixed point: a unit two per cent small produces two per cent more
symbols and reproduces itself exactly. Rounding each run on its own
converges instead, because every run votes independently. The grid is
then the right way to extract the bits, where rounding runs one at a
time drifts.
- A clipped first repeat used to truncate every other repeat to its
length. The consensus is taken over the commonest length now.
761 -> 869 tests.
Two additions, both about turning a number into something meaningful.
A band column. Next to every frequency -- on the live display, in the
line-per-hit output, in saunterbrowse's list and details -- is the name of
the band it falls in. 421 MHz is the 70 cm amateur band, and being told
so is quicker than remembering where the edges are.
The names come from the existing preset table, so there is one band plan
to keep right rather than two, but naming is not the job that table was
shaped for: several presets cover any frequency, some of them whole-tuner
sweeps that say nothing. So the candidates are ranked. Sweeps and the
"-complete" duplicates are dropped outright. The narrowest of what is
left wins, because it says the most -- 146.52 MHz comes back as the 2 m
simplex calling channel rather than as the whole 2 m band. Two exceptions
where the narrowest would be the wrong answer: ISM yields to the
allocation it shares (433.92 is 70 cm first, 915 is 33 cm first), and
shortwave broadcast yields to amateur where the two overlap, because
3.9-4.0 and 7.2-7.3 MHz are Region 1 and 3 broadcast but Region 2 amateur,
and this plan is documented as Region 2. 6 MHz really is 49 m shortwave
and is left alone.
The name is written into each capture's sidecar, so it travels with the
recording and an edit to the plan later cannot rewrite history, and
saunterbrowse searches on it: /70 cm finds the band without anyone having
to remember 420-450 MHz.
A map. A licence says where its holder is, so a list of callsigns is also
a map. Callsigns heard during a scan are now looked up as the transcripts
come in, announced on the display, and written to callsigns.kml in the
output directory; saunterbrowse --kml builds the same file from recordings
already on disk, and the two continue one map rather than starting two.
One placemark per station, not one per transmission: the same repeater
heard twenty times in an evening is one operator, and twenty pins on one
rooftop would say less than one. Each pin carries the callsign, the
licensee, the town, the grid square, and every frequency and time it was
heard on. The file is read back on open and added to, so later scans
build it up rather than replacing it.
Where a licence has no coordinates the grid square's centre is used and
the placemark says so -- a square is kilometres across where an address is
a street. A callsign with no licence at all is still recorded, in a
folder that starts switched off, because that a station was heard is worth
keeping even when nothing says where. A file already there that is not
readable as KML is never overwritten.
Also fixed along the way:
- The hit list's "no signals recorded yet" placeholder was one cell short
of its row, so it landed in the SNR column and wrapped, making the panel
taller than the layout had budgeted for and scrolling the display off a
short terminal. The identification column can no longer wrap either,
which is what _hit_capacity has always assumed.
- Licence lookups now record coordinates. The cache is versioned so that
entries written before this are asked about again, rather than pinning
every station to its grid square for good.
- CallsignBook.wait dropped joined threads; an all-night scan calls it
after every transcript and the list only ever grew.
- Tests redirect XDG_CACHE_HOME, so a run no longer reads or writes the
real lookup cache.
676 -> 761 tests.
Under the transcript, headed DETECTED CALLSIGNS:, every callsign heard in
it with the name and location on its licence.
Finding them is not one regular expression over the text as written. A
speech recogniser is poor at callsigns -- they are not words, they are
said one character at a time -- so it breaks them wherever the speaker
paused and writes the phonetic alphabet down verbatim. The recording that
prompted this has "Alright, KU 0W" in it, with a space; spelled out it
would have been "kilo uniform zero whiskey". All three forms read back to
KU0W.
Not inventing them matters more. A run of words is accepted only when
none of its parts is an ordinary English word: "or 3. Can you open 4" and
"CC1 boy", both from real transcripts here, fit the shape once the
punctuation is gone and are not callsigns. A single token said in one
breath is still trusted, because W1BOY is a perfectly good callsign, and a
lone "a" or "i" cannot start a join or "a B4U player" becomes AB4U.
Across the 126 transcripts in the recordings directory that turns three
candidates into the one that was actually said.
Lookups use the FCC's own licence data at callook.info -- no account, no
key, the callsign the only thing sent. They never delay the display: the
entry reads "looking up" and fills itself in, and results are cached under
~/.cache so a net recorded night after night is looked up once.
--no-lookup contacts nothing and still describes a callsign from its own
structure, the ITU prefix giving the country and the digit the US
district, which is also all there is to say for callsigns outside the US.
--callsigns prints everyone who identified themselves and where they were
heard.
Also asked: are transcripts appended to, or overwritten, when another
transmission arrives on the same frequency? Neither could be shown from
reading the code alone, so there are now three tests that run real scans
and look at the files. By default each transmission has a transcript of
its own -- the timestamp is in the name, so two overs cannot land on one
file. With --combine there is one recording per frequency and therefore
one transcript, opened for append with the time of each over; a second
scan into the same directory adds to it rather than starting it over,
which is the case the last of the three tests covers.
The browser and callsign tests refuse to reach the network at all. One
test did, quietly, and passed -- visible only because the assertion it
failed printed a real operator's address.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016PsWPTweCT6pwxKngvVxcg
A long scan leaves hundreds of recordings, each with a JSON sidecar of
measurements and, where a recogniser heard speech, a transcript. Reading
that meant opening files one at a time and guessing which were worth
playing.
saunterbrowse is a second executable in the same package. Arrow keys move
through the recordings; the transcript of whichever is highlighted fills
the top of the screen, because that is the part anyone actually wants to
read. Enter plays it, handing the file to whichever player is installed
-- the recordings are ordinary WAVs, every desktop already has something
that plays them, and a browser that cannot start would be worse than one
that cannot play. t opens the whole transcript full screen when it is
longer than the panel, and says so rather than cutting the end off
silently. / filters on the frequency, the name, the identification, or
anything that was said, which is the point of it: "was the repeater
mentioned" is a question about content.
Sidecars are read only for the rows on screen, so a directory of ten
thousand recordings opens instantly. Where there is no transcript the
panel says which of the reasons applies -- Morse (decoded, and shown),
data, a bare carrier, or speech never offered to a recogniser -- because
those want different things done about them. It only ever reads.
Two things were only found by driving it through a real terminal.
sys.stdin.read(1) goes through a buffered text wrapper, which in cbreak
mode waits for more bytes than one keypress provides: the program drew its
first frame and then hung, while tests against a stand-in stream object
passed. It reads the file descriptor now, and the tests drive a pty. And
stopping playback signalled only the direct child, so a player that is a
wrapper script kept the sound going with nothing on screen to stop it; the
whole process group is signalled instead, which is what start_new_session
was there for.
man saunterbrowse ships beside man bandsaunter, and the two point at each
other.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016PsWPTweCT6pwxKngvVxcg
A trunked system keeps one frequency transmitting a data stream around
the clock so its radios know where each conversation has been put. There
is no speech on it and it never stops, which makes it the strongest and
most useless signal in the band: the scanner parked on 856.561 MHz for
the full record limit, saved four minutes of buzzing, and found it again
on the next sweep.
Five signatures, matched against a constant-envelope stream that never
pauses: 3600 baud two-level (Motorola SMARTNET/SmartZone), 9600 (EDACS),
1200 (MPT-1327), 4800 four-level (P25 or DMR Tier III), 2400 (NXDN).
The first two are believed at once -- nothing else sends at those rates
without pausing. The rest share their shape with a digital voice call on
the same system, so they wait for the carrier to run unbroken past
--control-seconds, longer than a conversation goes without a breath.
Being in a trunked allocation raises confidence but is never required;
trunking is licensed on business pairs all over the spectrum.
One is named on screen, abandoned within a second or so, and its capture
deleted. --keep-control records them for a decoder; --lockout-control
writes them into the lock-out list.
Three things had to be fixed to get there.
The simulator's "pseudo-random" symbols were a counter: multiplying the
symbol index by an odd constant and taking it modulo the level count
returns the low bits, so two-level FSK came out 0,1,0,1. Every FSK test
in the suite was measuring a tone. Its FSK is now shaped the way GFSK
and C4FM shape a stream, too, square-edged keying being a signal no
licensed transmitter would radiate.
The symbol-rate estimator locked onto harmonics -- 3600 baud read as
18000 -- because a transition impulse train is a comb of equal lines; it
now walks down to the fundamental. The squared envelope is no longer a
candidate: it is not a transition signal, and its DC lobe made every
random OOK signal measure ninety baud. The search starts at 200 Hz
rather than 40, below which it was reading drift, which is how a bare
carrier was awarded a symbol rate. And a clean two-level signal counted
zero discriminator levels, because its modes land in the first and last
histogram bin, where find_peaks cannot see them.
Separately: locking out a frequency wrote to the settings file even under
--no-config, which has no settings file by definition. It now writes
only where it read from, and --simulate never writes at all -- an
invented frequency would sit in a real config for ever, skipping whatever
genuine signal happened to land near it.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016PsWPTweCT6pwxKngvVxcg
Every setting now carries a paragraph saying what it is in everyday terms
and why someone who does not already speak radio would turn it up, down,
on or off: what the squelch knob actually is, why automatic gain is a bad
idea for scanning, why a bias tee can damage equipment, why setting the
transcription language matters on noisy audio. The menus and
`config --describe` show it alongside the existing technical detail.
packaging/make-man.py generates bandsaunter(1) from that same table, so the
manual cannot document a setting the program lacks or miss one it has --
tests check both, that the page renders through groff without a single
warning, and that the guidance survives into the rendered output. Around
it are hand-written sections on the commands, entering frequencies, the
band plan, lock-outs, the keys during a scan, HF, single sideband, files,
environment variables and worked examples.
The .deb regenerates and installs it rather than shipping a copy, so an
installed manual always matches the installed program.
The README picks up what the last few commits added: the plain display as
a saved setting, what the settings tests now guarantee, and where to read
the manual before installing.
Version is the day's build: 2026-08-22_01.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
No speech recogniser is in Debian, so installing bandsaunter from a .deb
left transcription to a manual pip step on every machine. A repository of
one's own is not bound by archive policy, so build-repo.sh now packages
faster-whisper and the base.en model alongside the application:
bandsaunter the application (Architecture: all)
bandsaunter-transcribe faster-whisper, vendored (amd64)
bandsaunter-model-base-en the model, so nothing reaches the network
The wheels land in /usr/lib/bandsaunter/vendor rather than dist-packages,
and transcribe.py appends that directory to sys.path -- appends, so an
apt-managed numpy or PyYAML still wins and the vendor copy only fills the
gap. Duplicates of what Debian already ships are stripped from the tree.
resolve_model() turns a bare "base.en" into the packaged copy when one is
installed, and leaves it alone to be downloaded when none is.
The app package recommends the other two, so "apt install bandsaunter"
brings the lot and --no-install-recommends still gets just the scanner.
Its postinst explains how to add a recogniser only when there genuinely
is not one -- including the case where apt has already unpacked the
recogniser package but not yet configured it.
Verified with the source tree hidden and no home directory: the packaged
CLI runs, and a real recording transcribes offline from the vendored
engine and packaged model while numpy still resolves to the system one.
apt itself resolves the repository over HTTP and plans all three.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Versions are now the release date and a revision within that day, padded to
two digits so they sort as text: 2026-08-21_01.
Neither packaging system accepts that form, so it is converted at the edge
rather than kept as a second version string that could drift out of step:
PEP 440 forbids dashes and underscores in a release segment, and a Debian
version may not contain an underscore at all. The date and revision in
__init__.py are the single source; pyproject reads the converted form, and
the tests check that pip and dpkg both order releases correctly.
packaging/build-deb.sh builds a .deb with plain dpkg-deb. Every dependency
is already in Debian, so apt resolves the lot; the package also blacklists
the DVB-T driver that would otherwise claim the receiver. Deliberately not
debhelper: the payload is pure Python with nothing to compile, and this way
the build needs nothing installed beyond dpkg.
The speech recognisers are not packaged for Debian and can only come from
pip, so they are suggested rather than depended on -- transcription is off
by default and reports plainly when no recogniser is present.
README now documents every dependency with its package name on Debian,
Fedora and Arch, how to let a user reach the receiver, and how to check the
install worked.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
The Dust Council