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From July 2008 QST © ARRL
Table 1
FlexRadio FLEX-5000A, serial number 5107-5268
Manufacturer’s Specifications Measured in the ARRL Lab
Frequency coverage: Receive, 0.01-65 MHz; Receive, as specified (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 specified.
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 specified.
FSK, AFSK.
Receiver Receiver Dynamic Testing
CW sensitivity, 500 Hz bandwidth, preamp Noise Floor (MDS), 500 Hz bandwidth:
off/on: –123/–133 dBm. Preamp Off On
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 figure: Not specified. 14 MHz, preamp off/on: 28/15 dB.
AM sensitivity: Not specified. 10 dB (S+N)/N, 1 kHz, 30% modulation:
Preamp Off On
1.0 MHz 4.4 µV n/a
3.9 MHz 6.3 µV 1.6 µV
50 MHz n/a 3.7 µV
FM sensitivity: Not specified. For 12 dB SINAD:
Preamp Off On
29 MHz n/a 0.64 µV
52 MHz n/a 1.4 µV
Blocking gain compression: Not specified. 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 specified 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 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
0 dBm n/a
2
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 specified. Preamp off/on: +63/+59 dBm.
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 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
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).
Ugly Betty
The FLEX-5000A offers more features and
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