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).
Things worth knowing
- Firmware is incomplete. I've been able to do basic hardware checks, but actual power measurement and calibration isn't done.
- 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.
- Op-amps U1 and U2 have PTH and SMD package footprints.
- 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
