Mode JT9

JT9: narrow weak-signal amateur contacts.

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

Step-by-step: Tutorial-JT9

What JT9 is

JT9 is a weak-signal digital mode of the WSJT family, decoded by the same receiver as FT8.

Frequencies and settings

Setting	Value
Start frequency	14.078 MHz
Tuning range of the mode table	1 to 30 MHz
Sample rate asked	2 Msps
Lowest working rate	250 ksps
Channel width	3 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 WSJT, 14.078 MHz.

What OnAir shows

JT9 weak-signal contacts (9-FSK, convolutional code, 60 s periods, 15 Hz wide), 14.078 MHz.

The mode's own tab has these screens: Decodes, 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, Q65, FST4, MSK144, PSK31, JS8Call, RTTY, CW, SSTV, HamDRM, Olivia, Contestia, MFSK, THOR, DominoEX, Hellschreiber