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Introduction In previous posts I looked at various aspects of GMDSS/DSC using Scicos & GNU Radio (Ref.1/9). In this post I look at the underlying specification ITU M.493-16 and how the frame structure is assembled (Ref.10). The specification covers everything in great detail! It reminds me of working with X.25. I will generate a basic… Continue reading Marine GMDSS/DSC VHF Decoder_c

Introduction Receiving Satellite Weather signals at 136/138MHz has been very exciting over the past several years. NOAA15/18/19 are now deactivated, but Meteor M2-3 & M2-4 are still available. I was able to receive these signals at Toronto Harbourfront with an open sky view (Ref.1). However, at my home QTH, this proved to be difficult with… Continue reading Yagi Antenna for 138MHz Satellite Weather

Introduction Many satellite systems such as Meteor & Inmarsat use QPSK Quadrature Phase Shift Keying type modulation. There are various types of QPSK that enhance certain properties such as OQPSK Offset QPSK. We can simulate these signals in Scicos to study their differences (Ref.1). QPSK Scicos Simulation Figure 1 shows a Scicos schematic used to… Continue reading Satellite QPSK/OQPSK Simulation

Introduction When working with SDR# on Windows, I can save reception data using either the ‘Baseband: Simple Recorder’ or ‘Audio: Simple Recorder’. In either case the files can be opened and manipulated in Audacity because they have a .wav file extension. The Baseband files have a sample rate equal to the Rx samp_rate and the… Continue reading Trimming SDR IQ Raw Data