How do Software Defined Radios Work

Most of the buzz in the ham radio world these days is the advent of the Software Defined Radio -- SDR.  Although arriving in many forms, the general idea of an SDR is that an analog-to-digital converter (A/D) is used to convert an analog signal, say the received signal from your antenna or you voice signal from a microphone, to a digital representation.  The digital signal is processed by signal processing software that mimics the hardware elements in the transmitter and receiver described in Chapter 9 and 10.  This sound great but as we might expect there are limitations to this approach, mostly the high frequency performance of the A/D.  Chapter 12.  Software Defined Radios describes the sampling criteria and quantization that limit the signals an A/D can capture.  (Don't worry, no mathematics involved.)  An output of most SDR's are two signals that can be used to show signals in a spectrum or panadapter. 

Fred Cady,
Nov 20, 2018, 7:21 PM