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At resonance the imaginary part of R ( reflection coefficient ) is null , see the attached picture. This is because Z1 is a real number. In this case 50 ohm. Its very common to see that the SWR minimum are different to resonant frequency in a dipole because the real part of Z2 also changes with frequency. The question is what is better ? Minimum SWR or Resonance. From the point of view of energy transfer the minimum SWR is the dominant concept. The antenna current and charge distribution changes over the frequency and this modifies the radiation lobes, this is how the energy goes out the antenna , at resonance you have a maximum energy concentration ( you must to consider grand planes … its complex ) when I say energy is the energy that finally left the antena this is the incident power less the reflected power. If you want to have the better results both things must to happen at the same time.
This is the theory. In practical cases the effort to get that result will imply to add a match network with components with excellent quality, have no sense. In the other hand we have the output impedance of our radio equipment and believe me this is not a real number and the real part is not exactly 50 ohm… then all fine tuning considerations are really unnecessary.

There are much to say about but, all depends on your project. The results I saw for the antenna are excellent ,SWR= 1.08 is a dreamed value.

Regards, Patricio.


Ing. Patricio A. Greco
Taller Aeronáutico de Reparación 1B-349
Laboratorio de Calibración ISO 17025 AREA: RF/MW
Gral. Martín Rodríguez 2159
San Miguel (1663)
Buenos Aires
T: +5411-4455-2557
F: +5411-4032-0072
www.servicios-electronicos.com.ar