RTL-SDR for HF Marine GMDSS/DSC on SDRAngel – Telecommunications, Navigation & Electronics

Introduction

In previous posts I looked at decoding GMDSS/DSC HF & VHF signals using Multipsk on a Windows 10 Laptop & RaspberryPi4 (Refs.1/5). In this post I decode HF DSC signals using SDRAngel on a Windows 10 laptop.

GMDSS/DSC HF Reception

Parameter	MF/HF	VHF
Frequency	2187.5, 4207.5, 6312.0, 8414.5, 12577.0, 16804.5 KHz	156.525MHz
Baud Rate	100	1200
Character	10bits (#s 00-99) Error Correcting Code b1-7 info b8-10 parity	10bits (#s 00-99) Error Correcting Code b1-7 info b8-10 parity
Frame	6-7secs	0.5secs
Modulation	J3E USB(300,2700) nom 1700Hz/+-85Hz d_Mark/Space=170Hz	F3E/G3E NBFM 1700Hz/+-400Hz d_Mark/Space=800Hz
BW	800Hz	3500Hz

Fig.2 DSC HF/VHF Parameters

Fig.5 SDRAngel DSC Demod Sigcap on 12.577MHz 24m

Fig.6 SDRAngel DSC Demod Sigcap on 12.577MHz 24m

Figure 1 shows the RTL-SDR & 125MHz up-converter equipment setup. Figure 2 shows the GMDSS/DSC parameters. A text file is used to show the various various DSC frequencies + 125MHz to be used when tuning SDRAngel. Figures 3 & 4 shows the SDRAngel setup with a RTL_SDR receive device and two channel modules: an SSB decoder (for audio) and a DSC demodulator. Reception at 15/20MHz was very good (check WWV), so I was able to decode signals on 24m = 12.577MHz as shown in Figures 5 & 6.

Fig.7 YouTube Video RTL-SDR for HF Marine GMDSS/DSC on SDRAngel

Please send your comments, questions and suggestions to:
contact:

References

#1. – “VHF Marine GMDSS/DSC Decode & Scicos Simulation”
https://jeremyclark.ca/wp/telecom/vhf-marine-gmdss-dsc-decode-scicos-simulation/

#2. – “RTL-SDR for VHF Marine GMDSS/DSC”
https://jeremyclark.ca/wp/telecom/rtl-sdr-for-vhf-marine-gmdss-dsc/

#3. – “RTL-SDR for HF Marine GMDSS/DSC”
https://jeremyclark.ca/wp/telecom/rtl-sdr-for-hf-marine-gmdss-dsc/

#4. – “RTL-SDR for Marine GMDSS/DSC on RaspberryPi4”
https://jeremyclark.ca/wp/telecom/rtl-sdr-for-marine-gmdss-dsc-on-raspberrypi4/

#5. – “RTL-SDR for Marine GMDSS/DSC on Multipsk”
https://jeremyclark.ca/wp/telecom/rtl-sdr-for-marine-gmdss-dsc-on-multipsk/

#6. – “SDRAngel”
https://www.sdrangel.org/

#7. – “GMDSS A User’s Handbook”, Denise Brehaut, 6th Edition, Adlard Coles
https://www.amazon.ca/dp/B071JXWBWC/

#8.- “GMDSS Global Maritime Distress and Safety System”
https://en.wikipedia.org/wiki/Global_Maritime_Distress_and_Safety_System

#9. – “ITU-R M.493-15 Digital Selective Calling System for use in Maritime Mobile Service”
https://www.itu.int/rec/R-REC-M.493-15-201901-I/en

Introduction

GMDSS/DSC HF Reception

References

By Jeremy Clark