Antenna tuning or matching unit
Posted by
Elecraft mailing list on
Feb 21, 2018; 1:16am
URL: http://elecraft.85.s1.nabble.com/Antenna-tuning-or-matching-unit-tp7638335.html
This all depends on what is meant by antenna tuning.
When teaching newbies the wrong phrase can cause problems that are not seen till later.
Antennas are tuned with wire cutters or a hacksaw so the feed impedance is the desired value, ideally 50 ohm resistive or at least a match for the feeder concerned.
Of course that is not always practical so an antenna matching unit brings the antenna or antenna plus feeder input impedance to the value wanted by the transmitter.
Too often I have seen students believe the ATU alters the current and voltage distribution on the antenna so it looks exactly like the distribution on a dipole of the correct length for the frequency concerned.
Granted the currents and voltages might change as the ATU is adjusted but that does not make the antenna radiate more efficiently. The reflection at the feeder/antenna junction is unchanged.
In training we use the term antenna matching unit, AMU, to avoid best we can the students starting off with the wrong impression.
Amongst ourselves we can get away with slack terminology, we all know what is meant; in front of trainees it is a different story.
73 Alan G0HIQ
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