On this subject, it may be of interest to point to the article on my
website www.w3fpr.com "Antennas, Transmission Lines and Tuners". This
article first appeared in QRP Quarterly in July 2001.
I am pleased that DXzone has also recognized that article and has
included it in its Antennas/Theory category - see
https://www.dxzone.com/dx19232/antennas-and-transmission-lines-myths.html
There is not much math in the article, but you may find the concepts
valuable. The sections on "SWR as a friend" and "Antenna Tuners" is
particularly relevant to the current topic.
73,
Don W3FPR
On 2/20/2018 8:16 PM, Alan B via Elecraft wrote:
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.
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