A software-defined radio (SDR) is one in which functions such as tuning, filtering and modulating/demodulating are performed by software rather than hardware. The ease with which this is now possible is due largely to advances in digital electronics.
An SDR is essentiall a computer attached to an RF front end that performs the usual functions of detection and transmission of radio signals. The key physical component is perhaps the analogue to digital converter that connects the front end to the computer. The processing of the digital output is carried out by a CPU. This has a number of advantages:
- The need for special-purpose hardware is greatly reduced
- New functions can be added to the radio by changing or adding to the software
The cost of SDR devices is continually falling, and it has recently (as of April 2012) reached the point where the price is no longer an obstacle to the beginner. While high-quality SDR transceivers still cost over US$1000, a fair quality (but very usable) plug-and-play receive-only software radio can be had for as little as US$11, in the case of the RTL2832.
Other than a computer, a typical software radio requires these things:
- An SDR device to convert analog RF signals into digital data. Wikipedia has a good list of SDR devices.
- A computer program to demodulate digital data. See the List of SDR programs.
- An antenna suitable for receiving RF bands of interest
- An optional transverter or downconverter to “move” a section of the RF spectrum into a range the SDR device is able to tune to if you wish to receive transmissions outside the SDR’s native tuning range
- SDR forum Not exclusively for amateur SDR.
- RF Space manufacturers of the SQR-IQ, SDR-14 and SDR-IP software defined radios.
- HPSDR High Performance Software Defined Radio
- Ultra-cheap SDR mailing list – with a focus on using cheap SDR devices like the RTL2832
- Wikipedia:Software defined radio
- RTL-SDR Blog with information on using cheap RTL2832 SDR devices.