Weather FAX - 6338.6 kHz - Boston USCG

Weather FAX, also known as Radiofax or HF Fax, is a direct-to-print or direct-to-display transmission method used to broadcast graphic weather charts over high-frequency (HF) radio bands. While it might seem like "old school" technology in the age of high-speed internet, it remains a critical tool for mariners and meteorologists because it can be received thousands of miles away in the middle of the ocean without a satellite subscription.

The examples below were received on April 23, 11:50 PM EDT, on the frequency 6338.6 kHz USB. 

National meteorological services (like the NOAA in the U.S. or the DWD in Germany) broadcast a variety of charts:

• Surface Analysis: Shows high/low pressure systems and frontal boundaries.

• Wind/Wave Forecasts: Essential for ship routing and safety.

• Sea Surface Temperature: Used for both weather prediction and commercial fishing.

• Satellite Imagery: Low-resolution infrared or visible light images of cloud cover.

You don't need a specialized "fax machine" anymore. To see these charts yourself, you generally need:

1. An HF Receiver: An SDR (Software Defined Radio) or a traditional shortwave radio capable of SSB.

2. Antenna: A long wire or dipole tuned for the HF bands (usually between 3 MHz and 22 MHz).

3. Decoding Software:

   • fldigi: A popular open-source multi-mode program.

   • MultiPSK: A powerful tool for various digital and analog modes.

   • Black Cat HF FAX: Specifically designed for this mode.

Because it is an analog signal, the "noise" of the HF band often appears as "snow" or static lines on the final image, giving it a distinct, gritty aesthetic.

The NOAA Ocean Prediction Center provides a detailed list of products and their transmission schedules, which can be accessed here. For a more global perspective, the comprehensive Worldwide Marine Radiofacsimile Broadcast Schedules document is also available.