Mode Weather fax

Weather fax: HF radiofax charts for ships.

Group	Maritime
Default frequency	7.8781 MHz
Default sample rate	2 Msps
In the mode list	Weather charts, HF

Step-by-step: Tutorial-Weather-fax

What Weather fax is

HF weather fax stations broadcast weather charts and satellite pictures as slow analogue fax signals, mostly for ships.

Frequencies and settings

NAVTEX, DSC, weather fax.

Setting	Value
Start frequency	7.8781 MHz
Tuning range of the mode table	0.1 to 174 MHz
Sample rate asked	2 Msps
Lowest working rate	250 ksps
Channel width	10 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 Weather charts, HF.

What OnAir shows

Safety messages, distress and calling, fax pictures.

The mode's own tab has these screens: Fax, Stations, Tuning. 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: Receiving ship and coast-station broadcasts is legal in many countries, with limits on using or passing on private traffic. OnAir is a receiver. Check the rules where you live. See Legal.

Related pages

• All modes, Maritime
• Supported radios, Troubleshooting, FAQ
• More in Maritime: AIS, VDES, NAVTEX, DSC