Compaq manual FlexRadio Systems FLEX-5000A HF/50 MHz Transceiver, Expanding Your Vocabulary

product review

FlexRadio Systems FLEX-5000A HF/50 MHz Transceiver

Reviewed by Rick Lindquist, WW3DE	defined ham radio bar another notch.
NCJ Managing Editor

Key Measurements

Summary

		123
20	70	123	140
	20 kHz Blocking Gain Compression (dB)
		123
2	70	123	140
	2 kHz Blocking Gain Compression (dB)
		94
I3
20	50	99	110

20 kHz 3rd-Order Dynamic Range (dB)

I3
2	50	99	110

2 kHz 3rd-Order Dynamic Range (dB)

	33
I3	39†
20 -40	+35

20 kHz 3rd-Order Intercept (dBm)

I3		39†
2	-40	+30
	2 kHz 3rd-Order Intercept (dBm)

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 ama- teur market, and the newer software defined radio (SDR) technology remains far from ubiquitous in the modern ham shack. FlexRa- dio Systems now represents the vanguard of equipment manufacturers prodding the Ama- teur Radio community into the SDR era.

Let’s face it: Most equipment in today’s ham stations reflects only incremental im- provements in well-established wireless tech- nology, 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 “super- fluous.” In 2005 FlexRadio Systems nudged things off the dime again with its SDR-1000. The FLEX-5000A raises the software-

Expanding Your Vocabulary

Just as hams once fretted about grid drive, overmodulation and key clicks, the very na- ture of SDRs has given rise to a new crop of issues with names like “latency” and “sam- pling rate.” This is serious technology, and it’s not necessarily for the faint of heart.

In an SDR, analog RF signals are con- verted to a digital bit stream, and everything happens at that level using digital signal processing (DSP) techniques before conver- sion back to analog. As FlexRadio explains, its SDR is “essentially a direct-conversion receiver, but the mixing of the LO [local os- cillator] to create a 9 kHz IF makes it appear a lot like a dual-conversion receiver.” Some- thing 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

	I3				-34
	TX	-20
			Transmit 3rd-Order IMD (dB)			-35
	I9			-54
	TX	-20				-70
pr032			Transmit 9th-order IMD (dB)
	Key:	† Off Scale			80 M
	Dynamic range and intercept
	values with preamp off.				20 M
	Intercept values were determined
	using -97 dBm reference

Bottom Line

The FLEX-5000A builds on the suc- cess of the SDR-1000, retaining the top-shelf radio performance and adding features. The package is far less compli- cated, 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