Wednesday, May 28, 2014

Zeta SDR

Zeta SDR is a simplest SDR using analog mux/demux used as mixer to generate I and Q signals by mixing with oscillator signal of 45 degree phase shift, the IF signal is then passed through low pass filter. The circuit is from the web page

The basic block diagram is shown below.

The Crystal oscillator frequency should be 4X the required frequency to be received for example 40m band (7-7.2MHz) the crystal between the ranges 28-28.8MHz can be chosen. The 45 degree shift can be achieved digitally by using D-FF as shown.

It requires a sound card of stereo input on mic or line in. Sound card with larger bandwidth can give large spectrum. Usual soundcards have 40 KHz bandwidth. The software i used is SDR# which can be downloaded from here.

My prototype

Demonstration of Reception

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