Electrical engineer and circuit designer Ray Ring (of Circuit Salad) has created a revised version of his FV-1-based Mini SDR Radio, which replaces the CS2100 clock generator with an Si5351 generator. Ring explains, “The Si5351 has some advantages over the CS2100; namely, you can generate quadrature clks directly. This simplifies the hardware design and improves the quadrature accuracy.” He states the sideband rejection LSB/USB modes are impressive and hovers around 60 dB as well.
Beyond the Si5351, the Mini SDR Radio is equipped with an FV-1 audio processor, which handles all of the DSP processing, although it does require coding on an EEPROM memory, it allows for up to eight selectable programs, including AM/USB/LSB. The FV-1 also lets users utilize three analog POT inputs to control any parameters they require, such as gain, variable filter bandwidth, and depth. Ray admits his SDR has no tuned circuits or bandpass filters, but they can be easily added if needed.
Additionally, Ring's SDR features an OLED display and a rotary encoder for tuning, which has a frequency range of 2.7MHz to 25MHz. His design uses an LTC6252 low noise op-amp as an RF input with gain, providing a constant and dependable resistive RF termination for the sampling detector, which enables the use of random antennas to be used without affecting the detector.
A 16650 (3.7V) lithium rechargeable battery powers the Mini SDR Radio, and all electronics are neatly packed into a machined aluminum 1590A enclosure. Ring has a detailed walkthrough of his Mini SDR Radio on his Circuit Salad project page for those interested in recreating his build, which includes schematics and links to the necessary files needed to get the SDR up and running.