Introduction
In a previous post I looked at decoding GMDSS/DSC signals using Multipsk (Ref.1). Recently I have been able to use my balcony again and receive HF signals. This evening I was able to receive a GMDSS/DSC coastal signal on 36m using SDR# & Multipsk.
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 |
Figure 1 shows a summary of HF/VHF DSC parameters. This evening I was able to receive HF DSC signals on the 36m frequency of 8414.5KHz. Figure 2 shows the equipment block diagram. I also checked WWV for propagation conditions and was able to receive 10MHz/30m & 15MHz/20m well.
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References
#1. – “RTL-SDR for Marine GMDSS/DSC on Multipsk”
https://jeremyclark.ca/wp/telecom/rtl-sdr-for-marine-gmdss-dsc-on-multipsk/
#2. – “GMDSS A User’s Handbook”, Denise Brehaut, 6th Edition, Adlard Coles
https://www.amazon.ca/dp/B071JXWBWC/
#3.- “GMDSS Global Maritime Distress and Safety System”
https://en.wikipedia.org/wiki/Global_Maritime_Distress_and_Safety_System
#4. – “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
#5. – “GMDSS HF & VHF Wav Files”
https://www.sigidwiki.com/wiki/GMDSS_Digital_Selective_Calling
#6. – “Audacity”
https://www.audacityteam.org/
#7.- “MULTIPSK”, Ham Radio Software, F6CTE
http://multipsk.fr/index_anglais.html
