Fobos SDR Is a High-Quality Radio for Hobbyists, Researchers, and Professionals

There are a variety of software-defined radio devices currently on the market, each with its own advantage. For instance, some devices trade off performance for lower cost and provide users with hardware that is a good entry point to begin experimenting with SDR topics. On the other hand, higher quality devices are available that offer high-end performance but come at a higher cost. Another alternative has arrived on the scene looking to strike an optimal balance between cost and performance: the Fobos SDR, designed by Rig Expert, a small company created by four Ukrainian radio amateurs.

The SDR covers a frequency range of 100KHz to 6GHz. This is accomplished through a direct sampling receiver architecture for frequencies from 100KHz to 25MHz and a double conversion heterodyne architecture to cover frequencies 25MHz to 6GHz. The radio features three SMA connectors to interface the radio to antennas. Two connect to the direct conversion circuitry while the other routes to the heterodyne circuitry. The key circuits that make up the radio are RFFC5072 mixer and integrated synthesizer, MAX2830 direct conversion transceiver, and LTC2143 14-bit ADC. Furthermore, the ADC is sampled at 50MSPS allowing an output IQ sample rate of up to 50MHz. The radio boasts a frequency stability of +/-0.5ppm and has two additional SMA connectors for 10MHz clock output or 10MHz clock input.

Software support that is currently available includes popular SDR options such as SDRSharp and HDSDR. In addition, the full source code is available for a receiver complex IQ signal source block in GNU Radio. Instructions for use as well as application examples can be found through GitHub. It is worth mentioning that all these examples and commits are fairly new and recent. Which could mean support for other software platforms can still be coming. A complete user guide is also available to help with powering up the unit for the first time, installing drivers, and installing and configuring software.

Another point worth noting about the SDR is that it does not contain an FPGA or microcontroller. Instead, it utilizes an Infineon CYUSB3014 super speed USB controller to output the complex ADC data directly to the PC. This places the processing of the complex IQ data into the hands of the PC. This can add a degree of flexibility to the experienced user, allowing them full control over the digital signal processing chain. Currently, the radio does not yet seem to be available through any reseller outlets. However, Rig Expert products seem popular at HAM Radio Outlets. With that said, interested parties can keep an eye out on HAM Radio Outlets for availability.