Listening

Press Start scanning. The receivers sweep the bands you chose; whenever a channel is louder than the squelch (the dashed line on the chart), it opens and you hear it. Up to three channels can be open on one receiver at once; they are placed apart in your headphones, left to right.

The chart ↑

One bar per channel, and each bar is the spectrum inside its channel: what the receiver sees there, with a bright edge along the top. A voice fills its channel, a bare carrier stands up as one narrow spike, a signal leaning to one side of its channel may be off frequency. The white mark across a channel is its level as a whole, the number the squelch decides on. A bar with a label above it is being heard now. Dashed bars are channels the scanner passes over: locked out, muted, or skipped for a while. Not scanned marks the part of a band that no receiver covers, and a dim tuning is one its receiver is not looking at right now, because it is holding a channel on another tuning. Show the waterfall puts the waterfall under the chart: the spectrum over the last half minute, newest on top: every transmission a bright streak under its bar, as long as it lasted. Drag the bar under the waterfall to make it taller (up to a few minutes of history) or shorter; a double click on the bar brings the usual height back. The Chart page of Settings lets you choose whether the chart is drawn 10, 30 or 60 times a second (10 is the least work, 30 spares the battery), and how finely the receiver looks inside each channel: Normal, Fine or Finest. Finer steps show more of a signal's shape, and make the sweep a little slower.

Open channels ↑

Each channel being heard has its buttons:

Stay on this channel: the receiver keeps listening here, also when it goes quiet, so that you hear who answers. Press again to let the scanner move on.
Mute: keep receiving, but do not play it.
Lock out: never stop on this channel again. (Lock out until the app is restarted is the gentler one.)
Its name: type one, and the channel is saved.

Play speech only (in Settings, on the Listening page) keeps a channel silent until somebody talks on it: tones, data and empty carriers are not heard, and the first words are kept and played too. It is off to begin with.

When every receiver is busy, move on after a while (on the same page) is for the moment a transmission holds each of your receivers and nothing else can be heard: the receiver that has been on its channel longest leaves it after the seconds you set (a minute to begin with) and sweeps on, and it does not go back to that channel until the transmission has ended. A channel you have paused is never left. Switch it off to always hear a conversation to its end.

Morse code ↑

Every open channel is listened to for Morse: a repeater sending its call sign, an aviation beacon's identifier, radio amateurs talking in CW. While it is sent, the channel is marked ·– and what has been read so far is shown under its name, as it comes. When the transmission ends it stays in Heard recently and the Conversation, marked Morse.

A transmission often has Morse and speech in it — a call sign, then somebody talking. Each part is shown for what it is, in the order it came: Morse with what was sent, Speech with what was said (when speech to text is on: only the speech goes to it, never the beeps). Read Morse code (in Settings, on the Listening page) is on to begin with; switch it off if you never want it.

Radio amateurs send Morse by switching a plain radio wave on and off (CW). The CW mode is made for it: the wave is heard as a steady beep of about 700 Hz through a narrow filter, half a kilohertz wide, that keeps the stations beside it out, and a station a little off the channel is heard a little higher or lower. Amateur radio has the CW parts of 2 m and 70 cm as bands of their own, 2 m CW and 70 cm CW, in the CW mode. For a CW range or channel of your own, choose CW as the mode, give the frequency of the wave itself, and a width of 0.5 kHz. CW heard through USB or LSB is read too.

The demo has both: a repeater that identifies itself in Morse before somebody talks through it (Repeater, on 2 m), and a CW station calling on 2 m's CW part (CW calling). A scanner that comes by in the middle of a call leaves out the letter it came in on rather than guess it, so a call may begin a letter late.

What I want to hear ↑

The What to scan page of Settings is one list. Everything at the top switches the whole list on or off, except FM radio. Under it each group is a kind of listening, Aircraft, Boats and ships, Amateur radio, Walkie-talkies, with a switch of its own, and the bands that belong to it as rows under it, each with its own switch, how many channels it has, and, with several receivers, which receiver scans it. A group whose bands are partly on shows a mixed mark; pressing it then switches them all on, pressing again switches them off. FM radio stands alone: a station never stops, so while it is on nothing else is scanned, and switching any other band on ends it.

My ranges holds the ranges of your own, with Add a range of your own as its last line: a name, from and to in MHz, the channel spacing and width in kHz, and the mode. Other bands holds any band of the region that belongs to no group.

Saved channels holds one row per tag your saved channels carry, and Without a tag for those that carry none. A row switched on means those channels are scanned too, whatever their band's switch says; so a band off and a tag on scans just the channels with that tag. To scan only a handful of frequencies of your own, save them with a tag, switch Everything off, and switch that tag on. With several receivers each of these rows has a receiver choice too, and it wins over the band's: put the tower's channel under a tag on the receiver with the airband antenna, and that receiver listens to the tower while the other scans the airband without it. The choice counts while the row is on; a row switched off leaves its channels to their band.

Left out of scanning below the list keeps stretches the scanner passes over, whatever band they lie in.

Your lists ↑

Heard recently: every channel that was on the air today, newest first; replay a recording from here. Yesterday's are in the activity log.
Conversation: what was said, when speech to text is on (Recording and speech to text), and what was sent in Morse.
Saved channels: the channels you named, with their tags; each says whether it is scanned now, and can be locked out or muted from its row (and let in again). The tags' switches are in What I want to hear.
Locked and muted: to undo a lock or a mute; each channel with its name, when it has one.
Set aside: what KaikuSDR holds back on its own, apart from your locks. A channel that carries a steady, unmodulated carrier for five seconds, stays open for eight seconds with nobody speaking on it (on a CW channel: with nothing sent in Morse on it), or opens again and again for a moment with nothing said (five times in two minutes: bursts of data), is not a station: it is usually interference from the computer's USB, a hub or the dongle itself, and it would otherwise hold a dongle for as long as it lasts. The list says why and since when. A channel comes back by itself when a much stronger signal appears on it (a station over the interference), a carrier as soon as it is modulated; or press Let in to hear it anyway and never set it aside again; Lock out makes it your own lock instead. Nothing here is decided by the frequency, only by what is on it right now.

Audio for other programs ↑

The Sharing page of Settings has Audio for other programs: switched on, other programs on this computer (a decoder, a recorder of your own) can take what you hear from the address it shows — raw 16-bit stereo sound at 48,000 samples a second. Only programs on this computer can connect.

Profiles ↑

A profile is a copy of all your settings under a name: what you want to hear and where you are, the stretches left out, squelch and volume, listening, recording, speech to text, the chart and sharing. Set everything up the way you like it, open Profiles in Settings and save it as, say, "Home"; set things up another way and save "Cottage". From then on one click on a profile sets everything as it holds it, at once, while scanning. The page says which profile is in use, or that what is set up now is not saved as one; saving under a name that exists replaces that profile.

Not in a profile: your receivers and their own settings (they belong to the dongle that is plugged in), and what you have learnt — saved channels, names, ranges of your own, lock-outs and mutes. Those stay as they are whichever profile you use.