The Why And How Of Conjugate Matching
George Baker, W5YR
George's presentation will be delivered by James Duffey, KK6MC.
Many QRP operators use "non-resonant" antennas, either for multi-band convenience or out of necessity. Ladder-line or Twinlead is typically used to minimize feedline loss. The entire transmission system can be brought into resonance (reactances canceled), and the transmitter presented with its required resistive load, by means of an "antenna tuner" so that the available power of the transmitter can be delivered to the antenna. Departure from system resonance and/or use of an incorrect load resistance value results in less power being radiated and reduced transmitter efficiency.
When such a resonant system is properly designed and operated, a conjugate match prevails at each boundary between adjacent elements in the system. The presence and existence of these unique impedance matches make possible the efficient operation of non-resonant antennas with transmitters designed for a purely resistive load.
This presentation provides a brief overview of the operational theory of non-resonant antennas, transmission lines and tuners, together with a livel demonstration of the impedance and power levels in such a system.
George received the Class B license in 1946 at age 16 and a year later the Class A for phone operation on 75 and 20. The Extra came much later in 1954, along with a Ship Radar endorsement for his First Class Radiotelephone license.
After starting EE studies at Texas Tech College in 1949, he was in and out of amateur radio for the next several years while holding engineering jobs with RCA and GE. He completed graduate school at MIT in 1957 with an MSEE degree. His thesis research was a pulsed-Doppler radar receiver systems analysis.
George then joined Texas Instruments in Dallas and began work on the design and construction of TI's first digital computer. His 27+ year career at TI included research programs involving statistical data analysis by computer in the areas of underground nuclear seismic signal detection and medical EEG and EKG data. His work in computer data systems analysis included the design of the data communications sub-system of the TI Advanced Scientific Computer. At the time of his early retirement in 1985, George was responsible for the performance and availability of some 30,000 data terminals in TI's worldwide data network, an early private version of the Internet.
After retirement, he taught computer subjects in a local community college and was an Adjunct Professor at the University of Texas at Dallas teaching graduate and undergraduate courses in computer networking. He helped design and subsequently taught a 40-hour course in the fundamentals of radar to over 2000 TI engineers. Since full retirement from professional activities, he has concentrated on amateur radio and on computer systems for his home network. Along the way, he invented and patented a power control system for RV's.
George's amateur operation was on and off in the early years due to work and family commitments. He became active again in the early 70's with a strong interest in DX and again in the late 70's when his younger son became K5SR with an Extra at age 13. George discovered QRP in 1998 and has become an avid Fox Hunter. He emerged as Top Hound in the 2003-2004 Winter Hunts while his team, the NE-TXQRP Tornados, captured Team Championship honors.
Operation at W5YR today is almost entirely QRP CW. The present station consists of several Icom transceivers and a K2, with the Icom 756PRO2 being the workhorse. Wire antennas and a multi-band vertical carry the load for Fox Hunts and other QRP operating events.
He also has a sub-hobby of restoring quality test equipment for ongoing experiments and measurements. Time in the shack is probably 90% measuring and testing, etc. and 10% operating. Available time is spent at the computer trying to help others with technical problems by sharing over 58 years of amateur radio and some 50 years of professional engineering experience. He was recognized as Elmer of the Year at ArkieCon in 2003. George is active in two local QRP clubs, making regular technical demonstrations and presentations .
Antennas and transmission lines have long been an on-going interest. A friend of Walter Maxwell, W2DU, author of "Reflections II" among other publications, George has peer-reviewed several papers for Walt and gained much from this association. Computer programs that facilitate the prediction of antenna and feedline performance are of special interest. Experimental work in this area has resulted in a balun design, and in test equipment for evaluating balun operation, as well as a computer procedure for analyzing the entire antenna/feedline/tuner sub-system. He has also developed computer procedures for precision transceiver frequency calibration and frequency measurement. Of late, considerable effort has gone into the development of a rational practical viewpoint of the mechanisms and effects of conjugate matching with transmission line operation of non-resonant antennas.
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