DIY Radio QRP Digital Wattmeter

DIY Radio Summer 2021 Project -
QRP Digital Wattmeter

We have developed an accurate QRP watt meter to complement our Tuna Tin build. The meter measures power level from 10 mw to slightly greater than 11 watts over the frequency range of 3.5 through 450 MHz. The meter is accurate within 1.6% through VHF, and reads 6.9% low at UHF. The photo shows the assembled prototype measuring a 100 mW signal. Input and output connectors: BNC type. Power requirement: 9 volt battery or a 12 volt DC wall wart.

Please be aware this unit has primarily surface mount parts. The resistors and caps are all 0805 (.080 X .050”), the second largest surface mount parts commonly used. There are also two IC’s, size SOIC8. Neither of these are particularly difficult to solder but you are encouraged to view a YouTube video to acquaint yourself with the process. I sampled one called EEVBLOG #186. At about the 8 minute mark he shows working with the 0805 parts and at the 10 minute mark he works with the SOIC package.

The only thing you need to work with these parts is a set of tweezers, some small solder (.015-.020” will work nicely) and a small soldering iron. I also recommend an inexpensive magnifier. Harbor Freight sells a head strap magnifier for $4.99.

Should you feel you can’t deal with the IC’s I volunteer to install them for our members unwilling to try. The balance of the construction is your responsibility. There is a total of 30 size 0805 components.

The kits are out. Follow the action at https://www.groups.io/g/DIYRadio!

FLASH! ARRL has published this project in the October 2022 issue of QST!