RTL-SDR for VHF Marine GMDSS/DSC

Introduction

In previous posts I looked at decoding GMDSS/DSC signals using Multipsk (Refs.1/3). Recently I have been able to use my balcony again and receive HF & VHF signals. This evening I was able to receive a VHF Ch70 GMDSS/DSC coastal signal on 2m using SDR# & Multipsk.

GMDSS/DSC VHF Reception

ParameterMF/HFVHF
Frequency2187.5, 4207.5, 6312.0, 8414.5, 12577.0, 16804.5 KHz156.525MHz
Baud Rate1001200
Character10bits (#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
Frame6-7secs0.5secs
ModulationJ3E
USB(300,2700)
nom 1700Hz/+-85Hz
d_Mark/Space=170Hz
F3E/G3E
NBFM
1700Hz/+-400Hz
d_Mark/Space=800Hz
BW800Hz3500Hz
Fig1. DSC HF/VHF Parameters
Fig.2 VHF Equipment Block
Fig.3 SDR# Receive GMDSS/DSC_CH70
Fig.4 Multipsk Decode GMDSS/DSC_CH70

Figure 1 shows a summary of the HF/VHF DSC parameters. Figure 2 shows the VHF Equipment Block diagram. Figures 3/4 show the SDR# receive and Multipsk decoder screens.

Fig.5 YouTube Video RTL-SDR for VHF Marine GMDSS/DSC

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

YouTube Channel
YouTube Channel

References

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

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

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

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

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

#6. – “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

#7. – “GMDSS HF & VHF Wav Files”
https://www.sigidwiki.com/wiki/GMDSS_Digital_Selective_Calling

#8. – “Audacity”
https://www.audacityteam.org/

#9.- “MULTIPSK”, Ham Radio Software, F6CTE
http://multipsk.fr/index_anglais.html

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.