Read the Morse a station sends over its own carrier

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

packaging/bandsaunter.1

@@ -1,5 +1,5 @@
 .\" Generated by packaging/make-man.py -- do not edit by hand.
-.TH BANDSAUNTER 1 "2026-09-02" "bandsaunter 2026-09-01_01" "User Commands"
+.TH BANDSAUNTER 1 "2026-09-02" "bandsaunter 2026-09-01_02" "User Commands"
 .SH NAME
 bandsaunter \- scan, record and identify radio signals with an RTL-SDR
 .SH SYNOPSIS
@@ -1007,6 +1007,23 @@ 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