OnAirDecode KAWS with an SDR
KAWS: HF weak-signal chat and beacons, 2.4 kHz.
- In the mode list
- KAWS, 2.4 kHz HF chat
What KAWS is
KAWS: the HF weak-signal chat and beacon mode of the KAAL family, 2.4 kHz wide (eight profiles from chirp spread spectrum for the weakest signals to OFDM, LDPC blocks with CRC-16, a woven-lattice preamble, 15 s to 120 s UTC slots). Receive lists the chat messages and beacons that arrive, with the profile, SNR estimate and the preamble indicator, from upper-sideband audio; it only listens and….
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 KAWS, 2.4 kHz HF chat.
What OnAir shows
KAWS: the HF weak-signal chat and beacon mode of the KAAL family, 2.4 kHz wide (eight profiles from chirp spread spectrum for the weakest signals to OFDM, LDPC blocks with CRC-16, a woven-lattice preamble, 15 s to 120 s UTC slots). Receive lists the chat messages and beacons that arrive, with the profile, SNR estimate and the preamble indicator, from upper-sideband audio; it only listens and sends no acknowledgement. Transmit sends a chat message or a beacon one-way, repeated, to a radio or an IQ file. The slots come from the computer clock, which must be UTC-accurate. KAWS is simulation-only: it has never been on the air, and the voice profiles need a speech codec that you install.
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 KAWS
Can I decode KAWS 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 KAWS?
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 KAWS 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.