Antenna tuners
Posted by
Gary Peterson on
Jul 18, 2020; 8:00pm
URL: http://elecraft.85.s1.nabble.com/Antenna-tuners-tp7663365.html
You are in good company with Walter Maxwell, W2DU, now silent key. Maxwell was an engineer at RCA. He designed the antennas on several earth orbiting satellites and the antenna on the Lunar Rover. He explained this quite succinctly in his book Reflections (all three editions), by use of the conjugate matching theorem. As I recall, that chapter in his book (peer reviewed by the RCA engineering department) was called My Antenna Tuner Tunes My Antenna.
Gary, K0CX
But if the "tuner" is an LC network, like an adjustable L network, T network, Pi network, or a linked-coupled network, then I strongly disagree.
A tuner is a 2-port network. A transmission line is also a 2-port network. Both networks obey reciprocity, meaning that what you do to one port of the network will have a direct influence on the opposite end.
That being said, if an antenna exhibits a complex impedance at our frequency of interest, and that behavior can be corrected (brought to resonance) by the application of a particular value of reactance at the antenna's feedpoint, then that application of reactance can, for reasons of convenience, be made at the "shack end" of the transmission line. As such, the "tuner" in the shack is really "tuning" the antenna!
John, KD2BD
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