Really Simple QSD By Dan ka9rza Hello been awhile, but I found and idea I had before I learned to use LT Spice and decided to check it out in software and develop it. I have upload the LT Spice files and graphics of the plots so you can check it out. It looks like it is running pretty good, so I hope people can develop it.
http://f1.grp.yahoofs.com/v1/IEpnTGdS_cMLl5hP6_19F0MY1E2lNNTumqlKGjwD9k_yfU2s9KOKwoht4TgzZFdW-XPwdIMdoSU8IqHWIocts9Qkp8uU/KA9RZA/Really_Simple_QSD.zip or: http://groups.yahoo.com/group/soft_radio/files/KA9RZA/Really_Simple_QSD.zip The really Simple QSD was an idea I had for a really inexpensive Quadrature Sampling Demodulator made with a Phase Splitting Transform (L1, l2, C1, C2) and some capacitors, resistors and several 1N914 diodes. Enclosed in the Lt Spice Models folder are the Lt Spice files to run these QSD circuits. As well as two graphics of the circuit and the FFT plots showing the modulation and 90 degree phase shift of the I and Q outputs. Two models exist, one with two additional diodes for AM demodulation if needed. The AM detectors will be wide banded and so, will not stop you from detecting SSB or DRM etc. They are added for the purpose of extra rf removal to acquire more based band energy. In effect there is a rf filter capacitor following the AM detectors for the I and Q outputs. The rf transformer is resonant at 7 MHz with an input impedance of 50 ohms. 1 volt rf input is needed to drive the mixer section, the Lo In rf voltage is about 0.1 volt. You may tweak and perfect the idea more. These files are meant to aid people in experimenting with simple ideas to get them started with SDR radio projects. My Yahoo email is bouncing and so, I might not get messages here unless I change my email address, but I will check in to see if anyone tried this.
