OnAirDecode KAAL with an SDR
KAAL: digital voice with a station beacon, receive and transmit.
- In the mode list
- KAAL, 10 kHz voice
What KAAL is
KAAL: a 10 kHz wide digital voice and station-identity link (16 kbit/s voice codec, 16-QAM with LDPC, a sweep signature and a beacon side channel). Receive plays the speech and shows the last beacon (callsign, grid, position, power, text); transmit takes a microphone or a WAV file, to a radio or an IQ file.
Frequencies and settings
OnAir takes any frequency you type; the numbers above are the mode's starting point and the range its table describes. In the app the shortcut label is KAAL, 10 kHz voice.
What OnAir shows
KAAL: a 10 kHz wide digital voice and station-identity link (16 kbit/s voice codec, 16-QAM with LDPC, a sweep signature and a beacon side channel). Receive plays the speech and shows the last beacon (callsign, grid, position, power, text); transmit takes a microphone or a WAV file, to a radio or an IQ file.
Limits and what it was checked with
Checked with generated signals and impairments; recordings of real signals welcome.
Which radio you need
This is a shortwave mode, so the radio has to tune HF. An SDRplay, Airspy HF+ or an RTL-SDR in direct-sampling mode do that directly; with a HackRF an HF upconverter or a direct-sampling receiver is the usual route. A long wire or loop antenna matters more than the radio.
Receiving and the law
Questions about KAAL
Can I decode KAAL with an RTL-SDR?
An RTL-SDR can receive HF only in direct-sampling mode, which OnAir offers in its radio settings; results depend on the antenna. SDRplay and Airspy HF+ radios are better suited.
Is it legal to receive KAAL?
These are OnAir's own signal formats, still in development. Receiving them is passive. Transmitting needs the Arm button and your licence settings; check the rules where you live.
Can I try KAAL in OnAir without a radio?
Yes. Most modes include a built-in synthetic test signal, so you can open the screen and try the controls before you own a radio.