Software Defined Radio

Use panoramic displays with point-and-click tuning to find your next DX catch!

Something very exciting is transforming radio. It is transforming how we communicate throughout the spectrum, from VLF to she shortest microwaves. Instead of using equipment specialized for specific modes, with their inherent limitations, radio designs are emerging that do most of the work in the digital realm. In essence, hardware captures huge chunks of spectrum, digitizes it, and passes it to a digital processing core. The DSP then carries out functions of tuning, filtering, amplification, noise reduction, and demodulation. Multiple operators can use multiple virtual transceivers.

SOFTWARE DEFINITION REPRESENTS A QUANTUM LEAP IN CAPABILITIES! Here are examples of remote receivers you may tune now in your web browser (using java, javascript, and flash). These are basic multimode receivers representing the mere glimpse of what is possible:

Before reading more, point-and-click on one of the listed SDRs for a while, and recall that each change of mode, bandwidth, and frequency was once a carefully orchestrated dance of capacitors, crystals, inductors, and resistors. Excellent performance was difficult to achieve and maintain. In the digital realm, these dances are done, in software, in less time than it takes for the sound waves to leave your headphones and reach your eardrums! Now, have a look at the RF components of a basic software defined receiver:

Antenna servers consist of hardware at a receiving station with the function of capturing and digitizing signals for storage, processing, or listening by remote users. Users connect through the network to receive their desired signals, and the radio functions (mode, bandwith, frequency, etc) are provided by software at the client end of the connection (not at the antenna server).

Imagine a team of radio operators, scattered in different locations all connecting to one "antenna server." The operators actually use independent transcievers defined by software and limited only by the computing power of their equipment. The team could operate in any part of the spectrum, in any mode and bandwidth, with any processing needed for best effectiveness over the air. Multiple teams could form the ultimate monitoring or emergency communications network. A remote operator's station could be as simple as a laptop, proper software, and an internet connection to an antenna server. Networked computers, perhaps configured as a cloud, can provide immense computing power required for real-time RF signal processing and manimulation.

Amateur radio is already seeing quite a lot of innovation as shown in projects like the Quicksilver and Softrock SDRs. News organizations such as the BBC are moving to SDRs for their radio monitoring. Even military SDR applications are being implemented (i.e. PAVE PAWS radar). In this digitized world of radio, I find the performance already impressive. Listen to the SDRs linked above, and note the high quality of the receivers. The quadrature sampling WebSDR receiver started as hardware built "dead bug" style on a piece of copper clad PC board!! Are you impressed? Now, get thee not to a nunnery, but to the groups of creative people building the next generation of radio.

Here at AB9IL, I plan to post more SDR information as hardware and software are put into use here...I intend to use a Linux based system using a simple Quadrature Sampling Detector and Linrad for starters. Linrad is developing into a prime program for weak-signal work. It is flexible and based on some truly slick programming from the community of software defined radio operators. It looks good too:

Stay tuned for the latest in software defined radio developments!