Electronic – Antenna matching network topology


In tuning an antenna, there are multiple possible topologies that will take it to the middle of the smith chart.

Some differences that I can see between them are:

  • Component ESR (losses).
  • Effect of component tolerances.
  • Resulting antenna bandwidth.

For example:

Alternative 1 "LpCs"

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Alternative 2 "LpLs"

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Alternative 3 "LsCp"

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Which one would you choose and why?

Best Answer

Versions 2 and 3 offer a DC path to the antenna. If your antenna is a HF long wire, your protection from lightning strikes is not too good.
Smith charts imply you are talking UHF / microwave: antennas are smaller, lightning strikes are less common. If you have some form of masthead amplifier, you may actually want a DC feed.
Unless this is the case, I'd stick with version 1.