Introduction The GPS Global Positioning System is ubiquitous these days and can be even found equipped on all new smart phones. GPS information can easily be displayed on OpenCPN charts. GPS Global Positioning System The GPS system started as Navstar in the 1970s and became fully operational with at least 24 satellites continually orbiting the […]
Introduction The RTL-SDR receiver is a simple but very useful device. It can receive signals from 25MHz to about 1700MHz. It can be used to scan the aircraft VHF AM voice band from 118 to 137MHz and then the Marine VHF FM band from 156 to 164MHz. VHF Air AM Voice Frequency Band The VHF […]
Introduction In a previous post, I discussed how to use the Friis equation to determine the free space loss and receive level between a transmitter and receiver (Ref.1). Let’s consider an example that I saw in a recent sailing forum. The discussion was around the range of a typical marine VHF transmitter using a quality […]
Introduction In a previous post (Ref.1), I simulated an MSK144 modulator with Scicos. In this post, I will simulate the demodulator. Recalling the design parameters: -SSB Transceiver_USB interface (300,2700)Hz = 2400Hz-Baud Rate = 2000bdps, Tbaud = 0.500msec -MSK = Minimum Shift Keying, Frequency Shift = 0.5*BdRate = 1000Hz-Centre Freq = 1500Hz, Lower Freq = 1000Hz, […]
Introduction EPIRB or Emergency Position Indicating Radio Beacon Station is an emergency transmitting device that blue water sailors or explorers can use in case of distress. They have proven their worth over the years and are absolutely essential for anyone wanting to wander off the grid (Ref.1). At least 2000 people have been saved every […]