Circuit Salad's Ray Ring Redesigns His Compact FV-1-Based Software-Defined Radio — to Make It Bigger

Electrical engineer Ray Ring has returned to his FV-1-based mini software-defined radio (SDR) project, finding that the original design was a little hard to handle — literally, being too small for comfortable use.

Ring published his build log for his last mini SDR design earlier this year, having developed the idea around the FV-1 audio processor — which, Ring wrote at the time, "makes the base band signal processing a snap." Sadly, operating the device turned out to be not so easy: "Its too small! I made the thing so small; it’s hard to operate and assemble.

"So I decided to make it a little larger, allowing for all the controls to be larger and more spaced out. It has a larger display and the circuit board layout provides for the switches, encoder, volume control and display all to be soldered directly to the board. All of the circuit components are now on the top side of the board as well."

During the redesign, Ring also switched design flows to using a graphical computer aided design tool, SPINCAD, for FV-1 code development. "You can wire together functional building blocks and generate the required hex code for the FV-1 without writing any assembly code," Ring notes, while pointing out the Java-based tool is free and runs natively within Windows.

"Along with these physical changes, I made some minor circuit changes. These include: some component value changes, a different microcontroller, clocking the FV-1 at 48Khz with the third output of the SI5351 and adding a on/off power circuit which utilizes a momentary switch instead of a latching one. It now has a built in flat pack lithium ion battery that can be USB charged. I also refined the DSP demodulators and I am now utilizing a weaver demodulator for USB/LSB."

Ring's full write-up is available on the Circuit Salad website, along with the updated schematic.