We’ve been playing with the technology since the VoIPathon last year (many of us way before then).
What is SDR?
“Software-defined radio (SDR) is a radio communication system where components that have been typically implemented in hardware (e.g. mixers, filters, amplifiers, modulators/demodulators, detectors, etc.) are instead implemented by means of software on a personal computer or embedded system.” (wikipedia)
Here’s how the ARRL defines it:
“In its purest form, and SDR receiver might consist simply of an analog-to-digital convert chip connected to an antenna. All the filtering and signal detection can take place in the digital domain, perhaps in an ordinary personal computer. While there are still good reasons to use some analog components in high-performance gear, the SDR approach is becoming more common in Amateur Radio.”