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Navigation Telecommunications

RTL-SDR for Marine HF Weather Fax

Introduction

Up to date weather information is critical for sailors and can make the difference between a safe or a hazardous passage. Marine HF Weather Fax has been working reliably for many years and is an independent source of valuable information. NOAA’s Marine Weather Fax page (Ref.1) has all the information you need to use this resource. The instructional video from Jordan at Project Atticus (Ref.2) is excellent and covers all the basics to get you started. In this post I will review the Frequency Schedules, basic HF receiver equipment, and free software programs that can be used to decode the received signals.

Frequency Schedules

Fig.1 NOAA Frequency Schedules North America East Coast
Fig.2a Detailed Broadcast Schedule for Boston
Fig.2b Detailed Broadcast Schedule Boston
Fig.2c Detailed Broadcast Schedule Boston

Fig.1 shows the Frequency Schedules taken from the NOAA pdf that contains schedules for the whole world. Only North American East Coast stations are indicated here. Fig.2a – Fig.2c shows the Detailed Broadcast Schedule for Boston. Note that for a WEFAX signal at 6340.5KHz, the signal carrier frequency would be 6340.5 – 1.9KHz = 6338.6KHz since we operate in USB.

Fig.3 HF Receiving Equipment RTL-SDR + HamItUp NanoUpConverter
Fig.4 SDR# Controlling RTL-SDR + NanoUpConverter Receiving Boston 6340.5KHz
Fig.5 FLDIGI 4.1.14 Receiving WEFAX576

Fig.3 shows the RF equipment used to receive HFWEFAX. The standard RTL-SDR receives from 25 – 1725MHz, which does not include the HF band from 3 – 30MHz. In the figure the 1st generation of RTL-SDR is shown along with the latest version. In order to receive HF, a small up-converter is used. In Fig.3 a whip antenna is connected to the HamItUp Nano UpConverter which in turn connects to the RTL-SDR. All connections use sma connectors. The up-converter requires DC power, so this can be supplied by USB cable or via a BiasTee on the RTL-SDR. The YouTube video describes the connections.

Fig.6 WEFAX 72Hr Surface Forecast
Fig.7 48Hr Wind & Wave Forecast
Fig.8 YouTube Video RTL-SDR for Marine HF WEFAX

Please send your comments, questions and suggestions to:
jclark@clarktelecommunications.com

YouTube Channel
YouTube Channel

References

#1 – “National Weather Service Marine Radiofax Charts”, NOAA
https://www.weather.gov/marine/radiofax_charts

#2. – “Weatherfax Get WX Info Anywhere in The World”, Project Atticus
https://www.youtube.com/watch?v=l1QyDVgclto&list=WL

#3. – “FLDIGI Software”, W1HKK
http://www.w1hkj.com/

#4. – “SDR#”, SDR Receiver Software
https://airspy.com/download/

#5. – “RTL-SDR for AIS_2”
https://jeremyclark.ca/wp/nav/rtl-sdr-for-ais-2/

#6. – “RTL-SDR for AIS_1”
https://jeremyclark.ca/wp/nav/rtl-sdr-for-ais/

#7. – “RTL-SDR for Weather Radio”
https://jeremyclark.ca/wp/telecom/rtl-sdr-for-weather-radio/

By Jeremy Clark

Jeremy Clark is a Senior Telecommunications Engineer and Advanced Amateur Radio Operator VE3PKC. He is the author of E-Books on Telecommunications, Navigation & Electronics.