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Spring 2004 Issue |
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Software Defined Radio |
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After recently reading about Gerald Youngblood’s SDR-1000 HF software-defined transceiver,1 I obtained one. My experience with computer-controlled radio began last year with the ICOM PCR-1000. The software available was not really what I wanted, though. A search of the Internet produced nearly 30 different programs. The only program that actually expanded the functionality of the unit was TalkPCR.2 However, it was still just computer control of an existing radio system. The noise of the computer did little to enhance overall operation. I was able to obtain software to control my ICOM 756 PRO II and IC-910H. There again, it was just simple computer control, no added functionality. Enter the SDR-1000. In the simplest terms, it is a sophisticated detector in front of an analog-to-digital converter. The real magic is in the software that drives the transceiver. The computer software that comes with the unit allows decisions regarding demodulator (CW-L, CW-U, USB, LSB, AM, DSB, FM-N, Synchronous AM, DRM with additional software), IF gain, IF bandwidth, and many other features. The SDR-1000 panel presented by the software uses an oscilloscope display for signal spectrum representation (more about this later), with many “pushbutton” switches for various selections to operate the software. It’s very straightforward and intuitive. Because it is a transceiver, all of the above modes are available for the transmit mode. Currently, the power out is approximately 1 watt, with expansion to 40 watts planned. There is a complete VFO-A and VFO-B suite of pushbuttons to expedite your moves across the bands. My interest is in low-noise satellite reception, and that required a low-noise IF system to demodulate signals from the AO-40 and AO-27 birds. The current receive configuration is as follows: from a 3-foot rectangular BBQ antenna with Patch Plate,3 DEM .4 NF LNA4 to ADIC 37315 downconverter at 145 MHz to a DEM 144-28RX downconverter to the SDR-1000. Then using a coax switch, a side-by-side comparison of the 756PRO II and the SDR-1000 yielded the following results: On average, the beacon on AO-40 is 5– 7 dB stronger on the SDR-1000 than on the 756PRO II. With no test equipment on hand, it was impossible to verify this observing only the S-meters. However, there are times when we can copy the beacon with the SDR-1000 and not with the 756PRO II. With a beacon signal from the SDR-1000, it is always more possible to drive the ao40rcv2036 telemetry decoder with the SDR-1000 than it is with the 765PRO II or PCR-1000. Television/monitor horizontal oscillator signals, ever present with the 756 PRO II and other receivers, are non-existent with the SDR-1000.
The SDR-1000 requires a CPU over 600 MHz. My
system is a 2.8-GHz CPU, 1.2G RAM, and 256-meg video card with two sound
cards—Audigy and ADC’s Sound Max. The SDR-1000 requires a robust 1.5–2
amps, 13.8 volts DC. Click here to return to this month's highlights
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