A transciever is basically a box with alot of nice buttons and displays that transforms your voice in radio waves, and the radio waves back to sounds you can hear. More or less, this is done trough a complex process that includes many stages that take care of filtering, mixing, switching, amplifying, detection, modulating or demodulating and so on. Every one of these stages had it’s own role and required a certain complexity in order to achieve the required performance, and generally the better performance you want, the more parts you need and the more money you’ll have to pay.
But, we ARE in the 21st century, everybody knows what a computer is and probably has at least one in their house, and also knows what … magic a computer can do with the right software. So, why not implement all these functions required by a transciever into a piece of software running on a microprocessor, and let it filter, mix, switch, amplify, detect, modulate, demodulate or whatnot ? You would just need to find a way to interface the signal between the antenna and the software and you should be set. The advantages coming from using software instead of hardware would be many:
– hardware complexity reduced to a simple interface for basic functionality;
– performance of software filters, mixers, modulators etc is better and simpler to implement than that of hardware solutions;
– limitless functions, options, types of modulation etc, it only depends of the software used;
– posibility to monitor a wide frequency band (limited only by interface), not just one frequency like in classic trancievers;
Don’t let me make it sound like it’s my idea though because it’s not, it has been running around since computers were getting close to enough power to attempt this, back in the 80’s, and the first working models of such transcievers were used for military communications in the 90’s. How would a SDR transciever work exactly ? Go to the next page to find out.