A Software Defined Radio for the Masses, Part 4

We conclude this series with a description of a dc-60 MHz transceiver that will allow open-software experimentation with software defined radios. I t has been a pleasure to receive feedback from so many QEX readers that they have been inspired to experiment with software-defined radios (SDRs) through this article series. SDRs truly offer opportunities to reinvigorate experimentation in the service and attract new blood from the ranks of future generations of computer literate young people. 1 It is encouraging to learn that many readers see the opportunity to return to a love of experimentation left behind because of the complexity of modern hardware. With SDRs, the opportunity again exists for the experimenter to achieve results that exceed the performance of existing commercial equipment. Most respondents indicated an interest in gaining access to a complete SDR hardware solution on which they can experiment in software. Based on this feedback, I have decided to offer the SDR-1000 transceiver described in this article as a semi-assembled, three-board set. The SDR-1000 software will also be made available in open-source form along with support for the GNU Radio project on Linux. 2 Table 1 outlines preliminary specifications for the SDR-1000 transceiver. I expect to have the hardware available by the time this article is in print. The ARRL SDR Working Group includes in its mission the encouragement of SDR experimentation through educational articles and the availability of SDR hardware on which to experiment. A significant advance toward this end has been seen in the pages of QEX over the last year, and it continues into 2003. This series began in Part 1 with a general description of digital signal processing (DSP) in SDRs. 3 Part 2 described Visual Basic source code to implement a full-duplex, quadrature interface on a PC sound card. 4 Part 3 described the use of DSP to make the PC sound-card interface into a functional software-defined radio. 5 It also explored the filtering technique called FFT fast-convolution filtering. In this final article, I will describe the SDR-1000 transceiver hardware including an analysis of gain distribution, noise figure and dynamic range. There is also a discussion of frequency control using the AD9854 quadrature DDS.