Flex 5000.pdf

Product Review and Short Takes from QST Magazine

July 2008

Product Reviews:

FlexRadio Systems FLEX-5000A HF/50 MHz Transceiver

Short Takes:

QSL Maker

Key Measurements

Summary

product review

FlexRadio Systems FLEX-5000A

HF/50 MHz Transceiver

123

140

20 kHz Blocking Gain Compression (dB)

123

140

2 kHz Blocking Gain Compression (dB)

I 3

110

20 kHz 3rd-Order Dynamic Range (dB)

I 3

110

2 kHz 3rd-Order Dynamic Range (dB)

I 3

39 †

-40

+35

20 kHz 3rd-Order Intercept (dBm)

I 3

39 †

-40

+30

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 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-

defined ham radio bar another notch.

2 kHz 3rd-Order Intercept (dBm)

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

I 3

-34

-35

-20

Transmit 3rd-Order IMD (dB)

I 9

-54

-70

-20

Transmit 9th-order IMD (dB)

pr032

Key:

80 M

† Off Scale

Dynamic range and intercept

values with preamp off.

Intercept values were determined

using -97 dBm reference

20 M

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

table 1

Flexradio FLeX-5000A, serial number 5107-5268

Manufacturer’s Speciications

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.

Measured in the ARRL Lab

Frequency coverage: Receive, 0.01-65 MHz;

Receive, as speciied (sensitivity

transmit, 1.8-2, 3.5-4, 5.3305, 5.3465,

degrades below 0.2 MHz).

5.3665, 5.3715, 5.4035, 7-7.3, 10.1-10.15,

Transmit, as speciied.

14-14.35, 18.068-18.168, 21-21.45, 24.89-

24.99, 28-29.7, 50-54 MHz.

Power requirement: 12.4-15.2 V dc;

Receive, 1.6 A; transmit, 17 A;

receive, 1.5 A (typical); transmit, 25 A (max).

tested at 13.8 V dc.

Modes of operation: SSB, CW, AM, FM,

As speciied.

FSK, AFSK.

Receiver

Receiver Dynamic Testing

CW sensitivity, 500 Hz bandwidth, preamp

Noise Floor (MDS), 500 Hz bandwidth:

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 con-

sole , 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 prod-

uct. 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 (some-

times 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 re-

leases may have solved some of the issues

described in this review and can be evalu-

ated by the user community as development

progresses. Eventually, after extensive test-

ing, the changes find their way into the next

Official Release.

According to FlexRadio, the majority

of owners use three versions of PowerSDR .

They have the current Official Release for

backup and benchmarking, their favorite

stable SVN release for most operating, and

the latest SVN release to play with. More

information and a setup guide are available

off/on: –123/–133 dBm.

Preamp

Off

1.0 MHz

–122 dBm

n/a

3.5 MHz

–119 dBm

–129 dBm

14 MHz

–119 dBm

–132 dBm

50 MHz

n/a

–128 dBm

Noise igure: Not speciied.

14 MHz, preamp off/on: 28/15 dB.

AM sensitivity: Not speciied.

10 dB (S+N)/N, 1 kHz, 30 % modulation:

Preamp

Off

1.0 MHz

4.4 µ V

n/a

3.9 MHz

6.3 µ V

1.6 µ V

50 MHz

n/a

3.7 µ V

FM sensitivity: Not speciied.

For 12 dB SINAD:

Preamp

Off

29 MHz

n/a

0.64 µ V

52 MHz

n/a

1.4 µ V

Blocking gain compression: Not speciied.

Gain compression, 500 Hz bandwidth: 1

20 kHz offset

5/2 kHz offset

Preamp off/on Preamp off

3.5 MHz

123/120 dB

123/123 dB

14 MHz

123/122 dB

123/123 dB

50 MHz

n/a/118 dB

n/a

Reciprocal Mixing (500 Hz BW): Not speciied

20/5/2 kHz offset: –99/–99/–99 dBc.

Third-Order Intercept, 2 kHz offset: +30 dBm

39 dBM.

ARRL Lab Two-Tone IMD Testing

Measured

Calculated

Band/Preamp

Spacing

Input level

IMD level

IMD DR

IP3

3.5 MHz/Off

20 kHz

–25 dBm

–119 dBm

94 dB

+22 dBm

–10 dBm

–97 dBm

+33 dBm

14 MHz/Off

20 kHz

–20 dBm

–119 dBm

99 dB

+30 dBm

–6 dBm

–97 dBm

+39 dBm

n/a 2

0 dBm

14 MHz/On

20 kHz

–33 dBm

–132 dBm

99 dB

+17 dBm

–18 dBm

–97 dBm

+21 dBm

14 MHz/Off

5 kHz

–20 dBm

–119 dBm

99 dB

+30 dBm

–6 dBm

–97 dBm

+39 dBm

14 MHz/Off

2 kHz

–20 dBm

–119 dBm

99 dB

+30 dBm

–6 dBm

–97 dBm

+39 dBm

50 MHz/On

20 kHz

–33 dBm

–128 dBm

95 dB

+15 dBm

–22 dBm

–97 dBm

+16 dBm

Second-order intercept: Not speciied.

Preamp off/on: +63/+59 dBm.

from the FlexRadio Web site.

FlexRadio says PowerSDR will continue

to be open source, although certain control

functions are defined in closed-source firm-

ware in order to meet FCC requirements

to restrict transmissions on unauthorized

frequencies (the radio provides for MARS

and non US band operation).

flexibility than virtually any other transceiver

I’ve ever seen and possibly any other radio on

the market. I was disappointed in PowerSDR ’s

look and feel, however. The latest version of

PowerSDR is a Windows 98 implementation

in a Vista world. Although more feature laden,

cosmetically it’s very similar to the SDR-

1000’s “front panel” of an earlier PC epoch.

But even TV’s “Ugly Betty” has a boy-

friend. It’s what lies behind PowerSDR ’s

stodgy, less-than-stylish appearance that

Ugly Betty

The FLEX-5000A offers more features and

From July 2008 QST © ARRL

QS0807-PR01

Manufacturer’s Speciications

Measured in the ARRL Lab

FM adjacent channel rejection: Not speciied.

20 kHz offset, preamp on:

29 MHz, 59 dB; 52 MHz, 44 dB.

FM two-tone, third-order IMD dynamic range:

20 kHz offset, preamp on:

Not speciied.

29 MHz, 59 dB*; 52 MHz, 44 dB*;

10 MHz offset: 52 MHz, n/a. 3

S-meter sensitivity: Not speciied.

S9 signal at 14.2 MHz: preamp off,

50 µ V; preamp on, 50 µ V.

Squelch sensitivity: Not speciied.

At threshold, preamp on: SSB, 14 MHz,

0.02

0.04

0.06

0.08

0.1

0.28 µ V; FM, 29 MHz, 0.22 µ V;

52 MHz, 0.6 µ V.

Figure 1 — CW keying waveform for

the FLEX-5000A showing the irst two

dits in full-break-in (QSK) mode using

external keying. Equivalent keying speed

is 60 WPM. The upper trace is the actual

key closure; the lower trace is the RF

envelope. (Note that the irst key closure

starts at the left edge of the igure.)

Horizontal divisions are 10 ms. The

transceiver was being operated at 100 W

output on the 14 MHz band.

Audio output power: 10 dBV at 600 Ω .

As speciied. 4

IF/audio response: Not speciied.

Range at –6 dB points, (bandwidth):

CW (500 Hz): 345-856 Hz (511 Hz), **

Equivalent Rectangular BW: 499 Hz;

USB: 141-2851 Hz (2710 Hz);

LSB: 140-2850 Hz (2710 Hz);

AM: 71-3293 Hz (3222 Hz).

Image rejection: 70 dB.

First IF rejection, 43 dB 5 ; image

rejection, 88 dB.

Transmitter

Transmitter Dynamic Testing

Power output: HF and 50 MHz: SSB, CW,

HF: CW, SSB, FM, typically 100 W high,

FM, 100 W (high); AM, 25 W (carrier)

<1 W low; AM, typ. 25 W high, <1 W low;

QS0807-PR02

50 MHz: CW, SSB, FM, typ 99 W high,

<1 W low; AM, typ. 25 W high, <1 W low.

-10

Spurious and harmonic suppression:

HF, 51 dB; VHF, 61 dB.

-20

HF, >55 dB; VHF, >65 dB

Meets FCC requirements.

-30

SSB carrier suppression: >55 dB.

HF, 51 dB; VHF, 54 dB.

-40

Undesired sideband suppression: >55 dB.

HF, 61 dB; VHF, 60 dB.

-50

-60

Third-order intermodulation distortion (IMD)

3rd/5th/7th/9th order (worst case band):

products: –33 dB PEP at 100 W on 14 MHz.

HF, –34/–40/–48/–54 dB PEP;

-70

VHF, –21/–32/–39/–40 dB PEP.

-80

CW keyer speed range: Not speciied.

1 to 60 WPM.

-90

-100

CW keying characteristics: Not speciied.

See Figures 1 and 2.

f c -4

f c -2

f c

f c +2

f c +4

kHz

Transmit-receive turn-around time (PTT release

29 ms. 6

to 50% audio output): Not speciied.

Figure 2 — Spectral display of the FLEX-

5000A transmitter during keying sideband

testing. Equivalent keying speed is

60 WPM using external keying. Spectrum

analyzer resolution bandwidth is 10 Hz,

and the sweep time is 30 seconds. The

transmitter was being operated at 100 W

PEP output on the 14 MHz band, and this

plot shows the transmitter output ±5 kHz

from the carrier.

Receive-transmit turn-around time (tx delay):

25 ms. 6

Not speciied.

Composite transmitted noise: Not speciied. See Figure 3.

Size (height, width, depth): 9 × 9.3 × 12.4 inches; weight, 13 pounds.

Price: FLEX-5000A, $2799; antenna tuner option, $299; RX2 second receiver, $649.

*Measurement was noise-limited at the value indicated.

**Varies with CW pitch setting.

1 The level indicated is where the sound card’s ADC went into overload. Gain compression

could not be measured because of this behavior.

2 An input level of 0 dBm was higher than the ADC overload level, so the test was not performed.

3 No IMD product could be detected.

4 Audio output is dependent on external ampliied speakers.

5 Spur near the IF frequency. Note: The IF is in the audio range, so IF rejection will not

affect RF performance.

6 Measurements made with 1.6 GHz dual-core processor. Turnaround time may be faster with

higher speed CPU.

QS0807-PR03

-20

-40

-60

-80

-100

-120

package that’s free of the surfeit of wires,

cables, boxes and connectors that character-

ized the SDR-1000. (Further eliminating the

need for wires is VAC [virtual audio cable],

third-party software that routes signals for

digital programs to and from the FLEX-

5000A.) As one “Flexer” remarked on the

FLEX-5000A Web site, “fit and finish are

light years ahead of the SDR-1000” and “it

looks like a professional radio.”

This ham radio system essentially consists

really counts. The current maximum sampling

rate (more on this topic later) permits viewing

192 kHz of band spectrum, with immediate

access to both VFOs as well as to the panoply

of major functions, most common, some less

so. You access most functions via buttons,

sliders, menus and sub-menus or tabs.

-140

-160

-180

10 3

10 4

10 5

10 6

Figure 3 — Spectral display of the

FLEX-5000A transmitter output during

composite-noise testing. Power output is

100 W on the 14 MHz band. The carrier, off

the left edge of the plot, is not shown. This

plot shows composite transmitted noise

100 Hz to 1 MHz from the carrier.

“Light Years Ahead”

What the FLEX-5000A brings to the table

now is a far less complicated Amateur Radio

of the FLEX-5000A box and the PC. It of-

fers 100 W (PEP) on all bands 160 through

6 meters, general-coverage receive (0.01-

65 MHz, same as the SDR-1000) and lots and

lots of features, including several that weren’t

available on the SDR-1000. For example, the

newer model offers substantial improvement

in CW operation, VOX capability and other

novel and useful amenities, plus some impres-

sive performance statistics (see Table 1).

The close-in two-tone third-order IMD

dynamic range of the FLEX-5000A remains

comparable with that of the SDR-1000 and

of some of the best transceivers on the mar-

ket. On the SDR-1000, the best IMD DR

on 14 MHz at 2 kHz spacing was 99 dB at

the medium preamp setting, but as much as

10 dB worse at other preamp settings. On the

FLEX-5000A we measured 99 dB on 14 MHz

at all spacings, with or without the preamp.

The FLEX-5000A includes some features

that became viable simply because today’s

average PC is a lot more powerful than the

ones common in 2005. By the same token,

continued upward mobility of PC technology

is bound to further improve the FLEX-5000A

down the road, so enhanced performance and

additional features remain moving targets. In

addition, faster video cards can improve radio

performance by offloading of the CPU.

FlexRadio got rid of the gaggle of wires

that shackled the SDR-1000 and its associ-

ated high-end sound card by using a FireWire

(IEEE-1394) interface to handle signals

between the black box and the PC. Hurry ex-

plained that several essential “threads” travel

up and down the FireWire cable, including

receive and transmit I and Q signals (essen-

tially the radio’s IF) and receive and transmit

audio. The FireWire cable may be up to 10

feet long.

The “functional equivalent” of the SDR-

1000’s sound card and USB control now

resides in the FLEX-5000’s hardware. These

include low-level control and communica-

Switching computers Midstream

The “right” computer is key to satisfactory operation of the FLEX-5000A. We

started out with a high-end HP/Compaq dc7700p, which has an Intel E6300 Core

2 Duo processor (2 MB of L2 cache, 1066 MHz bus) running at 1.8 GHz. It was

equipped with 2 GB of memory, a RAID hard drive system and Windows XP Pro .

After we noted performance that was at odds with FlexRadio’s experience, the

manufacturer suggested that we try a Compaq Presario SR5310F with an Intel

Pentium E2140 Dual-Core processor (1 MB of L2 cache, 800 MHz bus) running at

1.6 GHz. This inexpensive machine came with 1 GB of memory and the Vista Home

Premium operating system. ARRL installed a FireWire card and removed the fancy

video card and all unnecessary applications that might bog down the processor.

Switching to the SR5310F demonstrated that you don’t need a blazing-hot,

high-end computer to run a FLEX-5000A. On the other hand, there were occa-

sions when it seemed that more computer muscle would have resolved some of

the issues we encountered. The FLEX-5000C model has a built-in Intel Core 2

Duo processor computer with 1 GB of RAM and XP Pro . — Rick Lindquist, N1RL

tion functions needed to run the specific

hardware. The FLEX-5000A has a device

driver just like any other PC peripheral. The

user must enter both the desired sampling

rate and buffer size into the driver dialog

box — which sets up the FireWire connection

parameters and something called “operating

mode” — as well as in the PowerSDR Setup

menu (or “form,” as FlexRadio calls them).

Our unit had the optional automatic antenna

tuner (ATU) installed. It can produce a rather

disconcerting symphony of grinding and whir-

ring as it tries to come to terms with whatever

load you have attached to one of the three

SO-239 connectors on the box’s rear apron

(Figure 4). The ATU has semi-automatic and

automatic settings as well as memory capabil-

ity. You can set the maximum SWR threshold

(up to 3:1). Unless you have the ATU tab open

on your screen, however, you may not know

right away if the tuner couldn’t find a match.

Although a tuner fault will not necessarily

switch the ATU to bypass mode, a red HIGH

SWR warning will flash when you transmit.

The FLEX-5000A’s transmit and receive

signal paths are completely independent,

opening new horizons of opportunity.

For example, at press time

an optional full-featured

second receiver, known

as RX2, was poised to

provide the potential for

SO2R — single-operator,

two radio capability — in

a single box.

Pegasus or SDR-1000 — or, for that matter,

ever controlled a conventional transceiver via

computer or Internet — appreciates that the

most significant part of the learning curve

is getting used to mousing rather than tried-

and-true dial twisting and button pushing.

FlexRadio’s slogan is “Real radios don’t

need knobs!”

Mouse control is an acquired taste. Think

of it this way: The front panel of the FLEX-

5000A is the graphical user interface of a

computer program, and, for better or worse,

the mouse has become the de facto control-

ler for programs ranging from accounting to

word processing. Last time I was in a Best

Buy store, the array of computer mice and

adjunct control devices was astonishing.

The FLEX-5000A’s tuning controls en-

able all the usual capabilities you’d expect

on a conventional Amateur Radio transceiver

and more. You can set (or reset) the tuning

step anywhere from 1 Hz to 10 MHz with a

mouse click, lock the VFO, operate “split,”

dump the contents of one VFO into the other,

equalize VFOs and listen to two frequencies

at the same time with the click of a button.

One disappointment was the minimal

“scratch memory,” a feature I’ve always

found extremely handy in contests. Clicking

SAVE retains a frequency, mode and filter,

but only for a single frequency. Some adept

programming that already may be on the

drawing board very likely could overcome

this minor deficiency.

The FLEX-5000A gives you a num-

ber of ways to tune. On the panadapter

display — the one you’re likely to use the

most — the radio lets you put a signal in

its crosshairs. Then click , you’re there,

aside from a little fine tuning (FlexRadio

calls this “ClickTune”). You can do the

same thing with the waterfall display. It’s

possible to choose a split panadapter/waterfall

or any combination of the two, as shown in

Figure 5. At the PowerSDR window’s normal

size, the menu to access this feature may not

be visible. It’s below the main console win-

Knobs ? We Don’t

Need No Stinkin’

Knobs !

Anyone who’s ever

used a Kachina, Ten-Tec

Figure 4 — Rear view

of the Flex-5000A.

Note the real analog

connectors here.

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