FlexRadio Systems Flex-3000 Product Review

From October 2009 QST © ARRL
In the Product Review for the FLEX-
3000 [October 2009, pp 45-51], in Table 1
we reported values for “Second Order Dy-
namic Range,” instead of our usual “Second
Order Intercept.” While this is valid data, it is
not a figure that members are used to seeing.
The corresponding second order intercept is
+69 dBm with the preamp off and +21 dBm
with the preamp on. Further testing proved
the figure with the preamp on to be rather
poor and lower than we’ve seen at the Lab
for other radios. Upon consulting FlexRadio
Systems, they acknowledged the problem
and came up with a modification to the radio
hardware and software to improve the sec-
ond order intercept with the preamp on. We
received and tested an updated FLEX-3000
at the ARRL Laboratory shortly afterward.
Results for the updated radio are shown in
Table 2.
Notice that there are now two preampli-
fication levels, instead of the one level in the
original design. Both of the new preamp set-
tings have improved second order dynamic
range, resulting in higher second order
intercept figures. Third order IMD dynamic
range also improved considerably with the
new preamp modifications.
In the original review, we also reported
the reciprocal mixing as “better than 112
dBc.” This is the case with AGC on at certain
settings. To get a better understanding of
how noise from adjacent signals affect the
noise floor, we have provided before and
after data with the AGC off
FlexRadio Systems has informed us
that all FLEX-3000s shipped beginning in
September include the preamp modifica-
tions. To determine if your FLEX-3000
incorporates the IP2 upgrade, check to see
if the TRX board hardware revision is revi-
sion G or higher. Open PowerSDR and click
on SETUP/GENERAL/HARDWARE CONFIG/.
Look at the last letter of the TRX serial
number. If it is Rev G or later, it indicates
the IP2 improvement is in place. Contact
FlexRadio if you have an earlier version and
you desire to receive this upgrade. It will be
provided at no cost.
The provided software contained every-
thing needed to easily upgrade to Power
SDR v.1.18.3. The folks at FlexRadio
graciously worked with the ARRL Lab
to improve their product. It was a plea-
sure working with them. — Bob Allison,
WB1GCM, ARRL Test Engineer
Update to FlexRadio FLEX-3000
Product Review
Table 2
FlexRadio FLEX-3000, serial number 3109-0286
Test results before and after modification.
Noise floor (MDS), 500 Hz bandwidth:
Preamp off Preamp 1 Preamp 2
14 MHz, before: –120 dBm –135 dBm n/a
14 MHz, after: –121 dBm –126 dBm –135 dBm
Noise figure, before: 27 dB 12 dB n/a
Noise figure, after: 27 dB 21 dB 12 dB
Blocking gain compression: Gain compression, 500 Hz bandwidth:
20 kHz offset 5/2 kHz offset
Preamp off/on Preamp off
14 MHz, before 112/105 dB 112/112 dB
Preamp off/1/2 Preamp off
14 MHz, after 113/111/114 dB 113/113 dB
Reciprocal mixing, 14 MHz 20/5/2 kHz offset
Before, AGC on: Better than 112 dBc
Before, AGC off: 91/90/89 dBc
After, AGC off: 91/91/91 dBc
ARRL Lab Two-Tone IMD Testing
Measured Measured Calculated
Band/Preamp Spacing Input Level IMD Level IMD DR IP3
Before: 14 MHz/Off 20 kHz –23 dBm –120 dBm 97 dB +26 dBm
–14 dBm* –97 dBm +28 dBm
0 dBm* –13 dBm +7 dBm
After: 14 MHz/Off 20 kHz –22 dBm –121 dBm 99 dB +28 dBm
–14 dBm* –97 dBm +28 dBm
0 dBm* –13 dBm +7 dBm
Before: 14 MHz/On 20 kHz –40 dBm –135 dBm 95 dB +8 dBm
–37 dBm –97 dBm –7 dBm
After: 14 MHz/1 20 kHz –27 dBm –126 dBm 99 dB +23 dBm
–19 dBm* –97 dBm +20 dBm
After: 14 MHz/2 20 kHz –36 dBm –135 dBm 99 dB +14 dBm
–27 dBm –97 dBm +8 dBm
Before: 14 MHz/Off 5 kHz –24 dBm –120 dBm 96 dB +24 dBm
–15 dBm –97 dBm +26 dBm
0 dBm* –13 dBm +7 dBm
After: 14 MHz/Off 5 kHz –23 dBm –121 dBm 98 dB +26 dBm
–14 dBm* –97 dBm +28 dBm
0 dBm* –14 dBm +7 dBm
Before: 14 MHz/Off 2 kHz –25 dBm –120 dBm 95 dB +23 dBm
–15 dBm* –97 dBm +26 dBm
0 dBm* –13 dBm +7 dBm
After: 14 MHz/Off 2 kHz –26 dBm –121 dBm 95 dB +22 dBm
–14 dBm* –97 dBm +26 dBm
0 dBm* –14 dBm +7 dBm
Second-order Intercept, 14 MHz Preamp off Preamp 1 Preamp 2
Before: +69 dBm +21 dBm n/a
After: +69 dBm +55 dBm +45 dBm
ADC clipping level (single tone) Preamp off Preamp 1 Preamp 2
Before: –8 dBm –31 dBm
After: –7 dBm –13 dBm –21 dBm
*IMD level exceeds the threshold of ADC clipping. Single tone clipping reported above.
Two tone clipping occurs at –13 dBm.

FlexRadio Systems Flex-3000 Specifications

General

Brand	FlexRadio Systems
Model	Flex-3000
Category	Transceiver
Language	English