H.P. Friedrichs is a degreed electrical engineer (BSEE), inventor, and author with more than three decades of experience working in domains ranging from audio, medical, and radio, to software, automotive, and aerospace. At present, he is a Principal Engineer with Honeywell, involved in the design and support of specialized equipment used for testing and validating aircraft power generation products.

He has five U.S. patents to his credit and holds three radio licenses including Extra-Class Amateur (AC7ZL), Commercial Radio Operator with Radar Endorsement and GMDSS

Operator/Maintainer with Radar Endorsement. He is also a certified VE.

Friedrichs is the author of numerous technical articles appearing in a variety of magazines, newsletters, and web sites but is best known for his books The Voice of the Crystal and Instruments of Amplification. Now cult classics among "from-scratch" electronics experimenters, these books have enjoyed favorable reviews from the editors of such prestigious periodicals as QST, CQ Magazine, Practical Wireless, and Make Magazine.

H.P. Friedrichs lives in Tucson, Arizona, with his wife and his German Shepherd/laboratory assistant — who is prone to "borrow" books and tools but not return them.