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by Josh Rovero, KK1D

Updated: August 6, 2011

FLEX-1500TM is a trademark of FlexRadio Systems.

The FLEX-1500 front panel.

The FLEX-1500 rear panel.

FLEX-1500 features and specs from   FlexRadio Systems

The FLEX-1500 is a small (4 inches wide x 6 inches deep x 2 inches high) and relatively inexpensive (sub-$600) HF and 6-meter transceiver suitable for fixed or portable operation.   Power output is 5 watts on SSB and CW.   The transceiver uses a RJ-45 microphone connector, and 3.5mm stereo plugs for both the headphones and key jacks.   The back panel provides considerable flexibility for antenna hookups with receive only, 1 milliwatt transceive, and 5 watt transceive connections.   Additional connections for a 10 MHz reference oscillator, 12VDC, and FlexWireTM are provided. The FlexWire port is a DB-9 with a push-to-talk (PTT) output, a PTT input, a two-wire high speed bidirectional bus supporting the I2C (I squared C) protocol, line-level audio input and output, and power output (5 VDC at 250ma max).

The FLEX-1500 is a software-defined radio (SDR).   It requires a computer (for now, running Windows XP, 7, etc.)) to operate the provided PowerSDRTM software.   PowerSDR provides many features, and has (to my way of thinking) an overly busy graphical user interface.  I find the "Panfall" mode more useful for tuning than the other display modes.   The receiver side of the radio sounds very nice, and the DSP filters are really remarkable.  One huge negative -- FLEX does not provide software that works under the Linux operating system, while other SDR manufacturers (QS1R, RFSpace, etc) do.

Interfacing with Fldigi and other digital modes/logging software requires the use of Virtual Audio Cable (VAC), a 3rd-party software package. A virtual serial or com port program, like com0com or VSP Manager, is also handy for interfacing between the 3rd-party applications and the FLEX-1500.

Brian Lloyd, WB6RQN, has written a guide with clear instructions for connecting Fldigi to the Flex radios with VAC and Steve Nance's, K5FR, Virtual Serial Port Manager (VSP Manager).

I used the radio with headsets most of the time, a Plantronics USB via VAC, and a McKay wired directly for 3.5mm stereo and RJ-45 microphone.   There is a noticeable delay between beginning speech and actual transmission of the speech with the USB headset.  The same problem arises on CW using the radio's internal software keyer.  This issue is at least partially addressed in the newer USB drivers and FLEX-1500 firmware.

Unlike the earlier FLEX-5000 and FLEX-3000 radios, the FLEX-1500 uses a universal serial bus (USB) interface instead of IEEE-1394 FireWire.   The reduced bandwidth available over USB versus FireWire, as well as other cost-reduction elements of the design result in a 48 KHz max spectrum/panadapter width.   Several controls, like spur reduction (SR), can further reduce the max bandwidth.   Here's a screenshot.  

The radio works well, and I have had no problem with QRP voice, CW, and digital mode QSOs.

The software, owner's manuals and installation guides for all FlexRadios are available at the FlexRadio site.

Josh Rovero,
Aug 6, 2011, 2:24 PM