SDR Projects

SDR Tx Software
Software Defined Radio Transmitter Software, written by Peter Martinez, G3PLX. Takes microphone input and generates the I/Q output drive for a quadrature upconverter forming the heart of an SDR Transmitter.
The software offers : One or two soundcard operation, Tuning / CW tone output, automatic microphone gain adjustment, LSB/USB/AM/FM modes, amplitude and phase balance. or
Download the latest version SDR Transmitter software or

Several tested IQ Upconverter designs including one for 145MHz that could form the basis of a microwave transverter driver.
Pointers and suggestions to other ideas...
LF Upconverter for translating soundcard output direct to LF. Includes an all-pass 0/90 degree phasing network for single audio (non I/Q) outputs
OPA_AllPAss.xls All-Pass network design spreadsheet

SDR-IQ Linearity Tests
A short note describing the results of some two and three tone measurements on the RF Space SDR-IQ wideband digital receiver. Alhough only a quick and simple measurement, they show clearly that the concept of Third Order Intermodulation Product (TOIP) applied to wideband receivers is completely flawed. The IMP level barely changes with input power, whereas in a linear Rx, the intermods should change at 3dB per dB of input level

Then there is the effect of adding in a third tone, that can be of appreciably lower power. As an example, monitor the
2 * F1 - F2 thrid order product of two tones, eg at 20 and 24 MHz, then introduce a third compont, F3 for example at 16MHz. As the level of this tone rises, the IM product that is not related to F3, actually falls. ............. Work that one out!

Several good articles on SDRs, I/Q processing and DSP can be found on the links page

Software Defined Radio The basics behind SDR techniques.
A presentation given at the HF Convention in 2002
(Might be a bit out of date now, but has all the essentials)

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