HF QRP directional wattmeter

A compact directional wattmeter for portable operation. Forward and reflected power is shown simultaneously with 2 LED bargraphs for easy antenna tuning.
Power sensing is done with a tandem match wound on a BN43-202 core. The microcontroller is a ATmega32u4 with USB interface for firmware uploading and serial data out (PC logging, debugging, etc).

Created with KiCAD ver. 5.0.2

Things worth knowing

1. Firmware is incomplete. I’ve been able to do basic hardware checks, but actual power measurement and calibration isn’t done.
2. Diodes D1-2, D4-5, and D6-7 are for providing forward bias to the bridge to improve linearity and remove zero offset. 2 devices are shown in each position to give the builder the option of a PTH or SMD package.
3. Op-amps U1 and U2 have PTH and SMD package footprints.
4. The board was designed to fit the Polycase JB-35 enclosure. Untested https://www.polycase.com/jb-35 https://github.com/kf4mot/qrp-wattmeter/blob/master/docs/14531129045666870.pdf

Licensed under CERN-OHL-S V2. Julian White, 2020

Schematic