Mode JS8Call

JS8Call: weak-signal messages, heartbeats and relays.

Group	Amateur: digital
Default frequency	14.078 MHz
Default sample rate	2 Msps
In the mode list	Messaging, 14.078 MHz

Step-by-step: Tutorial-JS8Call

What JS8Call is

JS8Call is a keyboard messaging mode built on FT8 modulation, with directed messages, relays and heartbeats.

Frequencies and settings

Weak-signal keyboard messaging on HF (normal, fast, turbo).

Setting	Value
Start frequency	14.078 MHz
Tuning range of the mode table	1.8 to 30 MHz
Sample rate asked	2 Msps
Lowest working rate	250 ksps
Channel width	3.5 kHz

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 Messaging, 14.078 MHz.

What OnAir shows

Every frame in the passband, messages put together from their frames, heartbeats and CQs, relays, stations and their grids on a map.

The mode's own tab has these screens: Frames, Messages, Stations, Map. The other tabs (Overview, Receiver, Scan, History) are described on the Main window page.

Tips and caveats

• Checked with generated signals and impairments; recordings of real signals welcome.
• Which radio: 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.
• Try it without a radio: most modes include a built-in synthetic test signal, so you can open the screen and try the controls first.
• Receiving and the law: Amateur radio signals are meant to be received. Receiving needs no licence in most countries; OnAir does not transmit. See Legal.

Related pages

• All modes, Amateur: digital
• Supported radios, Troubleshooting, FAQ
• More in Amateur: digital: FT8, FT4, FT2, WSPR, JT65, JT9, Q65, FST4, MSK144, PSK31, RTTY, CW, SSTV, HamDRM, Olivia, Contestia, MFSK, THOR, DominoEX, Hellschreiber