Building the Hardrock 50 HF Power Amplifier for QRP Rigs
I love my Elecraft KX3 but as I learned on a mini-DXpedition to St. Martin this summer sometimes 10 or even 15 watts is not enough power to make a decent QSO rate, even with a resonant antenna. I know I could buy a 100w rig for travel, but I’d like to keep the KX3 and get more use out of it. The KX3 travels nicely, and the antennas, cables and batteries all pack down into a backpack that's convenient for air travel. There are several HF power amplifiers on the market designed for portable QRP radios, including the Elecraft KXPA100, the RM ITALY MLA100 and Chinese made MX-P50M which is currently “Amazon's Choice” for what that’s worth. After some research I settled on the Hardrock 50 which is a complete amplifier kit that is FCC approved for commercial sale by HobbyPCB.com . The amplifier is based on Jim Veatch's award winning design developed for the ARRL's 2nd Homebrew Challenge competition. The Hardrock 50 covers 160M - 10M bands and supports...