Anders Nielsen is again with a second software-defined radio design, the PhaseLatch Mini — a part of an ongoing effort to construct a highly-capable modular SDR platform powered by, of all issues, the 50-year-old MOS 6502 eight-bit microprocessor.
“The PhaseLatch Mini [is] an [STMicroelectronics] STM32-based direct-conversion SDR front-end paired with easy Python host scripts,” Nielsen explains of his creation. “GQRX reads samples via a USB FIFO, and tuning is dealt with on the {hardware} aspect via the [Silicon Labs] SI5351 synthesizer. With this setup, I used to be in a position to cleanly obtain HF, FM broadcast, and even experiment (with blended success) round 144MHz.”
This is not the primary software-defined radio Nielsen has constructed: the PhaseLoom, a chunkier design constructed as an add-on protect for the MOS 6502-powered 65uino single-board pc, served as a place to begin for the challenge. This time the basic chip has a bit assist: an STMicro STM32F103 microcontroller, which supplies twin simultaneous-sampling analog to digital converters (ADCs) — “important for correctly digitizing I/Q channels,” Nielsen explains, and one thing lacking from the final challenge that required the sign be piped into the soundcard of a separate pc.
The board’s design is impressed by the basic STM32 Blue Tablet improvement board, although with two SMA antenna inputs that join via a 100kHz low-pass filter providing 210kHz of complicated baseband bandwidth. There is a USB Sort-C connector for energy and knowledge, and this time round it does not want a separate analog output to a soundcard to hold the obtained alerts.
Together with the PhaseLoom, the PhaseLatch Mini is a part of Nielsen’s progress in direction of a versatile SDR powered by a MOS 6502 processor. (📷: Anders Nielsen)
“Since ADC efficiency relies upon closely on format,” Nielsen explains, “I upgraded the board to incorporate a correct floor airplane and clear separation between the delicate analog enter and noisy USB strains. The design is easy: seize I and Q via a passive LC [inductor-capacitor] low-pass filter for anti-aliasing, then feed them straight into the MCU’s ADCs.”
Extra particulars can be found within the video embedded above and on Nielsen’s web site; supply code and design information, together with Gerbers for manufacturing, have been launched on GitHub underneath an unspecified open-source license, with boards out there to order on Nielsen’s retailer at €26.71 (round $31) plus delivery.
