In 2002, the SDR-1000 was released along with PowerSDR, the Windows based software. This was the 1st 100w SDR transceiver available to hams. It required a high-end audio card and a fast PC to operate.
The hardware consisted of a Rx pre-amp & attenuator, a QSD mixer to translate the RF signals down to 11kHz, the low Freq. IF. The Tx hardware started with a QSE mixer to translate the RF signal up to the operating frequency. Both mixers used an onboard DDS VFO controlled by PowerSDR. The hardware was simple and performed well, but were subject to misalignment due to changes in temperature, etc. The SDR-1000 used a parallel port to talk to the PC.
Setting up the SDR-1000 required the user to have a working knowledge in installing hardware, software drivers and troubleshooting the system. RFI issues were common because the computer cables picked up RF. Also, in the early days of Flex new audio cards with superior properties was announced almost monthly! But, if you wanted a working SDR transceiver, this was the only way to get it!
In the Spring of 2007 FlexRadio announced a new series of SDR transceivers! The high-end audio card or Codex was built into the radio! This eliminated the variability in performance, the rats nest of cables and simplified cabling to the PC. PowerSDR had greatly improved in 5 years, but some problems were evident. The radio hardware was linked to the PC via Firewire, a high speed serial port that carried the I/Q data streams from one or two receivers and the transmitter. Those data streams were processed in the PC in near realtime. The result was a high performance radio that was NOT as reliable as traditional rigs and had an annoying delay (latency). The Receiver had poor image rejection outside a narrow range and also had spurs or birdies because the analog parts of the radio were still subject to alignment errors over time. Also using a PC with Windows to support a near realtime process, was problematic! Anything that slowed down Windows; viruses, DPC's, disk fragmentation, IRQ conflicts, operator errors… you name it - reduced the performance of PowerSDR with increased latency, strange noises and PC crashes! Ubiquitous Windows was never intended to do realtime DSP processing. So the radio got a reputation for being finicky. Contesters tended to steer clear and experimental types, including eSSB'ers overlooked this because of the otherwise superior performance.
At the Dayton Hamfest in 2012, FlexRadio released a bombshell, the
Signature series Flex-6000 radios! The new radio hardware now employed
DDC on the Rx side and DUC on the Tx side - eliminating all the
unreliability, poor image rejection and spurs of a QSD/QSE design! The
RF spectrum is directly sampled with an ADC at 245.76 Million
samples/second in 16 bit chunks. In addition, all DSP processing occurs
in the radio, not the PC which eliminates all Windows problems
and greatly reduces latency! The 6000 series connects to a PC or other
device via the Ethernet. The PC running SmartSDR only acts like
a virtual front panel for the radio. The client SmartSDR software does
not process the I/Q data streams. So if the PC crashes, the radio still
works! Additionally the 6000 Series embedded processors are totally
isolated from Windows gremlins.The device running SmartSDR can be anywhere in the world or your desk! SmartSDR will be ported to OS-X Macs, iPads, Androids and other devices. Perhaps a smart hardware front panel with all the controls and indicators will be built. It too will have an Ethernet port to connect to the radio.
I think FlexRadio's 6000 Series will set the standard for eSSB'ers for years to come. I'm told by Gerald that SmartSDR is considering using a 12dB/octave highpass filter @ 50Hz instead of the brickwall cutoff currently used in PowerSDR! Also Tx bandwidth maximum maybe extended to 10 to 12 kHz! Latency will be noticeably improved in the 6000 Series radios because the onboard processing is dedicated to SmartSDR and nothing else! This OM can't wait to use it.
73,
Alan K2WS
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