Example Regional Coverage Analysis In the 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). The example was for an AIS Class B transmitter on a sailing yacht communicating with another boat at a distance of 10 nautical miles. […]
Friis Equation A basic equation relating to propagation in free space is the Friis equation (Ref.1). This gives the receive power in terms of transmit power, antenna gains, frequency of operation and separation distance. Basically it is saying that a point source of power is spread out over the surface of an ever expanding sphere […]
Introduction OFDM Orthogonal Frequency Division Multiplexing is a digital transmission scheme designed to give optimal data performance and selective fading protection over a band limited channel. Data is shared over a series of individually modulated carriers. OFDM is now pervasive over many different transmission systems. Typical applications include: Digital Television, DRM Digital Shortwave Broadcasting, DSL […]
Introduction 64QAM or 64 Level Quadrature Amplitude Modulation is a digital modulation technique used as a basic building block within the OFDM Orthogonal Frequency Division Multiplexing waveform used in Cellular Telephony LTE & 5G networks (Ref.1). QAM modulation encodes information into the different amplitude and phase levels of a carrier wave. Construction One way to […]
Introduction In the previous posts I looked at MSK144 and FSK441 which are WSJT-X/WSJT digital communications protocols or so called “fast modes” used for Meteor Scatter. In this post I will look at FT8 (Ref.1 & Ref.2) which is part of the WSJT-X series of protocols used for weak signal communication over all the HF/VHF […]