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Anleitung Zusammenfassung
Intercept values were determinedusing -97 dBm referenceKey:† Off Scale Reviewed by Rick Lindquist, WW3DE NCJ Managing Editor As we said in May 1998 QST when reviewing the first commercially available strictly computer controlled Amateur Radio transceiver, the Kachina 505DSP: “The relegation of functionality from hardware to software and firmware opens broad vistas of future capability.” Are we there yet? Or did our flight to nirvana get canceled? A decade down the road, Kachina is kaput in the amateur market, and the newer software defined radio (SDR) technology remains far from ubiquitous in the modern ham shack. FlexRadio Systems now represents the vanguard of equipment manufacturers prodding the Amateur Radio community into the SDR era. Let’s face it: Most equipment in today’s ham stations reflects only incremental improvements in well-established wireless technology, form factor and human user interface. Additionally a “knob mentality” persists, despite Kachina’s confidence, expressed 10 years ago, that owners of its milestone radio would embrace mouse-and-keyboard operating to the extent that knobs would become “superfluous.” In 2005 FlexRadio Systems nudged things off the dime again with its SDR-1000. The FLEX-5000A raises the software- defined ham radio bar another notch. Expanding Your Vocabulary Just as hams once fretted about grid drive, overmodulation and key clicks, the very nature of SDRs has given rise to a new crop of issues with names like “latency” and “sampling rate.” This is serious technology, and it’s not necessarily for the faint of heart. In an SDR, analog RF signals are converted to a digital bit stream, and everything happens at that level using digital signal processing (DSP) techniques before conversion back to analog. As FlexRadio explains, its SDR is “essentially a direct-conversion receiver, but the mixing of the LO [local oscillator] to create a 9 kHz IF makes it appear a lot like a dual-conversion receiver.” Something called a quadrature sampling detector (QSD) — 0°, 90°, 180° and 270° — is at the heart of all FLEX models. This generates the “I” in-phase composite and “Q” quadrature signals. Are your eyes glazing over yet? FlexRadio points out that direct- conversion receivers like the SDR-1000 and FLEX-5000A don’t require band-pass or roofing filters. Because the QSD doesn’t respond to signals below its passband but is susceptible to odd harmonics above its LO Bottom Line The FLEX-5000A builds on the success of the SDR-1000, retaining the top-shelf radio performance and adding features. The package is far less complicated, shedding the many wires, cables, boxes and connectors that characterized the SDR-1000. Be prepared to experiment with the software and settings to get the most from this radio, however. Mark J. Wilson, K1RO . Product Review Editor . k1ro@arrl.org From July 2008 QST © ARRL frequency, FlexRadio uses a low-pass filter to block signals above its cutoff frequency. The rationale here, the company explains, is that low-pass filters have lower loss and wider component tolerance than band-pass filters. While indisputably a direct descendant of the SDR-1000, the FLEX-5000A is a new and far slicker model that makes the earlier unit seem more of a beta test product than something ready for shrink wrap. A lot has changed in the intervening years; some has remained essentially the same. PowerSDR — the Face of the Future? In Zen terms, the radio is one with its GPL open-source PowerSDR software. Well, not quite. As FlexRadio Support Staffer Dudley Hurry, WA5QPZ, told me, “80% of the radio is in the computer.” Not only does PowerSDR serve as the radio’s virtual front panel, or console, it handles all DSP functions, including modulation, demodulation, metering (digital and analog) and filtering. The black box with its hypnotic bright blue pilot light provides the physical portals — and many of them — into and out of the virtual world where the real radio resides. For the benefit of Flex cognoscenti, our unit ran PowerSDR version 1.10.4, at the time the latest Official Release, throughout the review process. It is important to keep in mind that any review of a software defined product is a snapshot in time. FlexRadio and their user community are constantly working on enhancements and upgrades to this product. As time marches on, the FLEX-5000A with a later version of the software will be different from the radio reviewed here. Many of the concerns and observations we make might be resolved by the time you read this, or at some time in the future. The operation, performance and feature set change regularly in both obvious and subtle ways. For those who enjoy adventures in software, new PowerSDR test versions are available for download on a regular (sometimes daily) basis. To take advantage of the latest version under development you must install and set up TortoiseSVN, a program that manages the various files and versions (SVN stands for Subversion). The SVN releases may hav...