I must also add a little word. I built my first SDR over ten years ago. It was based on the SoftRock plans (One oscillator, a 74AC74, a 4066 and a PC with a sound card).
I couldn't count the hours listening to the VLF and the HF bottom end. I then bought and assembled two official kits (a SoftRock RX Ensemble II HF and a SoftRock RXTX Ensemble Transceiver wired for the Citizen Band as I am only a SWL). I have to admit that even if the 11M band is more or less closed these days, I realized real little feats using the Watt of my SoftRock, JS8Call, ROS and a simple hand cut dipole!
Today I'm trying to develop a SDR receiver similar to the SoftRock but autonomous (ARM ?P, 16 bit ADC & touch LCD). All the signal processing is written and gives results similar to those obtained with a computer. I have to finish the assembly and it is not an easy task. It will probably remain a personal project, I would probably need some help to make something serious out of it. I'm also trying (with relative success) to write modulators and demodulators (RTTY, PSK, Hellschreiber ...) and you know what ? I always start by testing them with the help of my SoftRocks as signal source. Nothing easier than opening a sound card and getting the samples!
It's strange, I remember when this all started more than ten years ago. It's totally amazing what you can do with a handful of judiciously assembled components to receive radio signals. Life is Weird.
