Lite + Xtall RX V9.0 Schematic

Posted on Feb 6, 2014

Below is the main schematic of the RX + Xtall V9. 0 SDR. The schematic has been partitioned into separate stages, each of which is covered in a separate page of build instructions in this web site. You can click on each shaded area and view the corresponding stage builders` notes. This receiver is patterned on the classic `direct conversion` receiv

Lite + Xtall RX V9.0 Schematic
Click here to download the full size of the above Circuit.

er, in that it mixes incoming RF down to audio frequencies by beating the RF against a Local oscillator such that the mixer products are in the audio frequency range. Unlike the traditional DC receiver, the SDR does not "tune" the local oscillator`s frequency to beat up against a desired RF signal. Instead, the local oscillator generates a fixed, "center frequency. The beauty of an SDR design is that the operator can, in one display, "see" all activity within the design bandwidth and immediately "click" on any interesting signal within that spectrum. This version (9. 0) of the Softrock SDR receiver has a programmable local oscillator (U4 in the schematic below), permitting the operator to select any desired center frequency. Frequency selection is done in a SDR program on the PC, and implemented via a USB connection and control circuit (U2 in the schematic below). The local oscillator is the Silabs Si570, of which there are two versions: LVDS - which requires U5, a high-speed, differential receiver that translates LVDS levels, with a typical differential input threshold of 100 mV, to LVTTL signal levels While it would be tempting to use that frequency progammability to directly tune the oscillator to a specific desired frequency, the SDR design for Version 9. 0 follows the SDR paradigm of providing a "chunk" of spectrum that is simultaneously detected and presented for processing in the PC. To accomplish this, the SDR...

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