Flex-6000, new generation of SDR transcievers


Flex Radio Systems introduced yesterday at the Dayton 2012 Hamvention the all new Flex-6000 series of transcievers, called “Signature Series”. These are the first comercially available SDR products intended for HF amateur use that employ Direct Digital Conversion, sampling RF directly thanks to the high-performance Analog Devices AD9467 ADC without the need for mixers such as the Tayloe detector that was the heart of the previous generations of SDR equipments.

But this is not the only thing the FLEX-6000 series brings: it’s purpose seems to change a bit towards better integration into the modern digital world as a shared resource. If until now a transciever was a piece of equipment one operator would use at a time, the FLEX-6000 series is a computer network equipment anyone can use (either on LAN or via Internet), allowing up to 8 virtual 384KHz bandwidth¬†recievers in the 0.03-77 MHz range to be created and operated simultaneously. Ideal for club stations or conditions that require remote operation (Radio Arcala comes to mind), even though the transmission is limited to one user at a time.

Other hardware key points are the pair of Mitsubishi RD100HHF1 finals conservatively pushing out 100W at 13.8V, a rather unusual choice considering the other top manufacturers start moving towards 100V operated final stages wich offer better IMD figures and are easier to work with. Also, the main CPU is a Texas instruments ARM Cortex A8 1.2-1.4 GHz CPU with NEON coprocessor and 1.0-1.2GHz DSP processor. There will be 3 models available, the top dog FLEX6700 transciever, the FLEX-6700R reciever and the FLEX-6500 transciever, with rumored prices os US$7000, US$6000 and US$4000.

More details in the FLEX-6000 series presentation sheet.

Over-the-horizon radar operating in 27MHz


OTH radars are strategic military equipments that basically allow the operator to “see” beyond the horizon trough the means of ionospheric reflexion that allows HF signals to propagate all over the globe. Regular radars use signals in the GHz regions (better for detection of smaller objects) and are only good for direct visibility, that is why sometimes OTH radars were replaced by more expensive “flying radars” more commonly known as AWACS, but as the Cold War has ended armies are folding back to the cheaper technology and the OTH radard operating in HF are spotted more and more oftenly by amateurs. More details on the OTH Wikipedia page, if you are courious.

Such a signal could be recieved today in Bucharest between 27.480500 MHz and 27.499500 MHz at a S9 level, with a type of pattern I haven’t seen before. ¬†Feel free to check out the video and to see how it looks on my SDR transciever.

Software Defined Radio – next step in transciever technology


A transciever is basically a box with alot of nice buttons and displays that transforms your voice in radio waves, and the radio waves back to sounds you can hear. More or less, this is done trough a complex process that includes many stages that take care of filtering, mixing, switching, amplifying, detection, modulating or demodulating and so on. Every one of these stages had it’s own role and required a certain complexity in order to achieve the required performance, and generally the better performance you want, the more parts you need and the more money you’ll have to pay.

But, we ARE in the 21st century, everybody knows what a computer is and probably has at least one in their house, and also knows what … magic a computer can do with the right software. So, why not implement all these functions required by a transciever into a piece of software running on a microprocessor, and let it filter, mix, switch, amplify, detect, modulate, demodulate or whatnot ? You would just need to find a way to interface the signal between the antenna and the software and you should be set. The advantages coming from using software instead of hardware would be many:

– hardware complexity reduced to a simple interface for basic functionality;
– performance of software filters, mixers, modulators etc is better and simpler to implement than that of hardware solutions;
– limitless functions, options, types of modulation etc, it only depends of the software used;
– posibility to monitor a wide frequency band (limited only by interface), not just one frequency like in classic trancievers;

Don’t let me make it sound like it’s my idea though because it’s not, it has been running around since computers were getting close to enough power to attempt this, back in the 80’s, and the first working models of such transcievers were used for military communications in the 90’s. How would a SDR transciever work exactly ? Go to the next page to find out.