W2DU’s Son Read My Article—Then Corrected the Historical Record
Rick Maxwell’s email reveals the increasingly capable laboratory behind Walt Maxwell’s landmark work on reflections and conjugate matching.
Every technical writer hopes to hear from a reader who can add something the published record missed. Few expect that reader to be the son of one of amateur radio’s most influential transmission-line thinkers.
After reading my article Reflections Revisited: What’s Still True—and What’s Been Refined—Since W2DU, Richard A. “Rick” Maxwell, W8KHK, contacted me. Rick is the second son of M. Walter Maxwell, W2DU. His present callsign is especially meaningful: W8KHK was his father’s original call in 1933, when Walt was just 14 years old.
Rick’s message was generous and historically valuable. It explains how Walt’s laboratory developed from relatively simple bridges and couplers into a far more capable vector-measurement environment. It also adds first-hand context to the equipment, transmitter technology and theoretical assumptions behind his work.
Hello Joeri,
I enjoyed reading your analysis of the Reflections publications by my father, M. Walter Maxwell, W2DU.
I am his second son, Richard A. Maxwell, now W8KHK—which was Dad’s original callsign in 1933, when he was 14 years old.
I very much appreciate your analysis and review of his findings, and your comparison of what can be observed now with state-of-the-art equipment with what he employed in his earlier work.
You wrote that Maxwell’s tools included couplers, SWR bridges, directional couplers and oscilloscopes rather than network analysers. That is an accurate list for his earlier work, but his laboratory resources were upgraded over the long period that followed the start of this work in the mid-1960s.
Early on, he used rudimentary directional couplers and bridges. For better accuracy, he soon used the General Radio 1604 bridge; HP 606, 608 and 612 generators; a slotted line; the PRD 219; and an HP 415 meter.
When they became more affordable, during retirement soon after 1980, he acquired an HP 8640A generator, an HP 8405A vector voltmeter and its associated directional couplers, along with an HP 4815A vector impedance meter. It was with these instruments that he was able to validate the conjugate-match theorem with linear generators used in amateur-radio applications. He also acquired a Tektronix spectrum analyser with a tracking generator.
It is true that non-linear generators change the landscape and the results of matching calculations. However, when most of his work was done, vacuum-tube final amplifiers with traditional tank circuits or π-network coupling networks were commonplace, while solid-state finals with broadband filter networks were beginning to displace the earlier tube equipment. Class-D and class-E finals and SDRs were future innovations, as you mentioned.
Although HP vector network analysers were in use at the RCA Astro Electronics Division, he had no access to those resources after retirement. I believe it is reasonably safe to assume that the many sequential measurements made with the vector voltmeter and vector impedance meter could achieve results equivalent to those obtained with a vector network analyser, although with considerably more time and effort. The resulting Smith Chart plot would still be essentially identical.
I also appreciate that you mentioned the fact that many of the calculations assume “lossless networks”. These are, of course, purely theoretical and do not exist in practice. Unfortunately, many readers gloss over this and then question the power relationships when applying the conjugate-matching theorems referenced in the manuscript.
Joeri, I believe your document is clear and concise, complimentary to the work my father did, and helpful in allowing readers to view his work from the perspective of the tools available then and now. To make it more historically accurate, you might consider expanding the list of instruments he used over time. The later HP and Tektronix equipment provided a much more accurate and professional validation of his earlier work.
It appears to me that his intended guidance to amateurs, concerning practical coupling and matching techniques for this class of communications, retains lasting value for most readers.
Thank you again for taking the time to write your analysis. I am quite sure Dad would be pleased if he were able to read it today.
Warm regards,
Rick Maxwell, W8KHK
ex-WB4GNR, WB2HKX, AFC2HKX
Editorial note: Rick later gave me explicit permission to publish this message and invited me to remove repetition and make minor editorial corrections. It has been lightly edited for clarity, spelling and flow; its technical meaning has not been changed.
Rick’s historical detail is now part of the W2DU analysis
The expanded instrument history and its measurement context have been incorporated into the revised article. You will find that updated version first in the Maxwell reading path below.
Read Maxwell Again—with the Fuller Story
Rick’s message changes the historical lens through which these articles should be read. Begin with the newly updated analysis, then continue through three other essential RF.Guru articles about Maxwell, conjugate matching and RCA’s engineering legacy.
A Conversation Still Producing New Leads
My correspondence with Rick did not end with this first message. In our continuing conversation, he has shared additional links, memories and technical leads that deserve stories of their own—including Walt Maxwell’s later writing, family amateur-radio history, vintage transmitters and the practical laboratory culture surrounding this work.
We will explore several of those subjects in later editions of the RF.Guru mailing list, The Guru’s Incredible Lab. Rick has also kindly offered to review relevant manuscripts before publication, allowing us to combine documented engineering analysis with first-hand historical knowledge.
A Record Made More Accurate
The best outcome of technical publishing is not being treated as the final authority. It is creating a record that knowledgeable readers can test, refine and improve.
Rick Maxwell’s message does exactly that. It preserves the central value of W2DU’s work while completing the picture of how that work was tested over time. For that contribution—and for the trust involved in sharing it publicly—I am deeply grateful.