2022 SDR Transceiver

First of all I want to thank Jack (W8TEE) and Al (AC8GY) for providing the inspiration and practical guidance to allow me to tackle a SDR transceiver project. I didn’t feel comfortable taking on a SDR transceiver build until Jack and Al published their book and well commented code. Understanding the “signal flow” in DSP at the code level in terms of sample buffers, operations on those buffers, and moving between buffers was a big break through for me.

I highly recommend Jack and Al’s book which is available from Amazon.

January 29, 2023 Update. The transceiver was put on the air for the first time this weekend and several FT8 QSOs were completed on 40m and 20m. Since the previous update, the PA was completed based on TAPR Pennywhistle design using a pair of Mitsubishi RD16HHF1 RF Power MOSFETs. I am making one more iteration of the QSD, QSE, LO, & GPS Board to add audio low pass filtering at the input to the QSE, this should be completed in the coming weeks. The next major piece of code to be incorporated is AGC, as this is one of the more complicated pieces of Jack and Al’s code it will take some time understand and refactor.

December17, 2022 Update. The receiver hardware is fully functional and the transmitter hardware is complete up to the PA driver. I have refactored Jack and Al’s code to extract only the basic DSP receive and transmit routines at this stage. Necessary functions removed from the code will be added back in and tested one by one, e.g., AGC, as the build progresses. As the transceiver is to be used for digital modes with WSJT-X, the code associated with the T41-EP waterfall display has been removed. The receiver and transmitter (up to Tx PA Driver output) are working on 160m through 10m. The WSJT-X waterfall display looks very good on all bands with no artifacts.

The 2022 SDR Transceiver uses the following boards from the 2020 Transceiver:

• Backplane Board
• Front Panel Board
• Arduino & I2C Relay Control Board, but only I2C Relay Control circuitry populated.
• RF Band Pass Filter Board
• Transmitter PA Driver and Receiver RF Attenuator Board, with added Receive RF Preamplifier
• Transmitter Low Pass Filter and Antenna Switching Board

The following new boards have been built for the 2022 SDR Transceiver:

• Teensy 4.1, Transmit and Receive Audio Board
• QSD, QSE, LO, & GPS Board

SDR Transceiver Block Diagram.

SDR Transceiver top view (below) shows the boards plugged into the Backplane Board, from right to left:

• Teensy 4.1, Transmit and Receive Audio Board
• I2C Relay Control Board
• QSD, QSE, LO, & GPS Board
• RF Band Pass Filter Board
• Transmitter PA Driver, Receiver RF Attenuator and RF Pre-amplifier Board
• Transmitter Low Pass Filter and Antenna Switching Board

SDR Transceiver Top View

SDR Transceiver Side On View

SDR Transceiver Front Panel View

SDR Transceiver Rear Panel View