Say how strongly each sensor is being heard, and how much of it arrives

Two numbers rather than one, because "how well is this sensor coming in" is
two questions and they can disagree in a way that is worth seeing.

The first is strength: how far the sensor's burst stood above the noise of the
second it arrived in, in decibels, on every reading and in the log and the
spreadsheet.  The burst detector already worked this out and threw it away --
it is the ratio the per-burst threshold is set from -- so this is carrying a
number through rather than measuring a new one.

What it is not is a power at the aerial, and the docstring says so where
somebody will read it.  A dongle has no reference level and, with the tuner
left on automatic, no fixed gain either; anything in dBm would be invention.
A ratio of two amplitudes off the same receiver in the same second is the
honest quantity, and it is enough for the three things anybody wants a signal
reading for: comparing two sensors now, watching one over an evening, and
pointing an aerial.  A fixed --gain makes it comparable between runs as well,
which the help now says.

It is coloured red, amber or green, it is on the live display as well as the
report, and it is kept on a narrow terminal when other columns are dropped --
because somebody moving a whip about while a number climbs is not doing it on
a wide window, and that is the most useful thing this does.

The second is the share of what a sensor sent that actually arrives, which
comes out of the timing for nothing.  These transmit on a fixed cycle, so the
shortest wait ever seen between two of a sensor's messages is that cycle, and
the average wait is the cycle divided by the fraction getting through: one
over the other is the fraction, with no need to know the model or how often it
is meant to speak.

Read together they say more than either does alone.  A strong signal with a
low share is interference or a collision rather than distance.  A weak signal
at a hundred per cent is a sensor at the edge that is getting through anyway
and is best left alone.

The strongest of the three copies of a message is the one reported, not the
first: they go out milliseconds apart and arrive at whatever the fading does
to each.  A reading with no strength -- an older log, a block with no
measurable noise floor to be a ratio to -- leaves the last known figure alone
rather than overwriting it with a zero.

Full suite 2369 passed, checked against five deliberately broken builds
including the one that reports decibels as a power ratio, which is off by a
factor of two and looks entirely reasonable.  Built as 2026-09-07_06.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016PsWPTweCT6pwxKngvVxcg

README.md

@@ -2048,11 +2048,40 @@ mast        wind         14.2 km/h   3.1 km/h   0.0 km/h  38.6 km/h
 ```
 
 The two tables are split on purpose. The first is about reception — who, how
-often, how well — and is the one to look at when something is missing; `every`
-is the honest measure of an aerial, because these transmit on a fixed cycle,
-so thirty seconds from a sensor that sends every sixteen means half of them
-are being missed. The second is about the weather, and is the one to look at
-when nothing is.
+often, how well — and is the one to look at when something is missing. The
+second is about the weather, and is the one to look at when nothing is.
+
+### How well each sensor is heard
+
+Three columns of the first table answer that, and they answer different halves
+of it.
+
+**`signal`** is how far the sensor's burst stood above the noise, in decibels,
+coloured red below 14 dB, amber below 22, green above. It is a ratio of two
+amplitudes off the same receiver in the same second and nothing more — *not* a
+power at the aerial, which an RTL-SDR cannot give: it has no reference level,
+and on automatic gain it does not have a fixed gain either. What a ratio is
+good for is comparing one sensor with another at the same moment, watching one
+sensor over an evening, and pointing an aerial. Set `--gain 40` (or any fixed
+figure) if you want the numbers comparable between one run and the next;
+on automatic they drift with whatever the tuner decided.
+
+It is on the live display too, and kept there even on a narrow terminal,
+because moving a whip around while watching a number go up is the single most
+useful thing it does.
+
+**`every`** is the average wait between messages, and **`heard`** turns that
+into a share. These transmit on a fixed cycle, so the shortest wait ever seen
+between two of a sensor's messages *is* that cycle, and the average wait is
+the cycle divided by the fraction getting through — one over the other is
+therefore the share, without ever needing to know what model it is or how
+often it is supposed to speak.
+
+The two are worth reading together, and they can disagree usefully. A strong
+signal with a low share is interference or a collision with another
+transmitter rather than a range problem. A weak signal at a hundred per cent
+is a sensor at the edge that is nonetheless getting through, and is worth
+leaving alone.
 
 There is no average. These arrive every sixteen seconds when the sensor is in
 range and not at all when it is not, and rain and cold both shorten the range
@@ -2140,6 +2169,8 @@ aerial. These are a few milliwatts: a quarter-wave whip for 433.92 MHz is 17 cm
 of wire, which is the stock telescopic aerial collapsed to about that, and
 indoors behind a wall with the dongle in the back of a machine is usually the
 problem. Try `--gain 40` if the automatic gain control is not finding them.
+Once anything at all is being heard, the `signal` column on the live display
+is the thing to watch while moving the aerial about.
 
 **`peak` is well above `noise` and there are no bursts.** Something is there
 and did not group — usually a continuous transmitter rather than a keyed one,