Ham Radio: Impedance-2: What

[last updated: 2024-03-16]
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Impedance-1 - Why
Impedance-3 - Reactance
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• Impedance (Z) is like Resistance - it opposes ("impedes", duh) current flow, and it's measured in ohms, just like ordinary DC resistance.
• But it's different than pure resistance because the amount of resistance/opposition is different at different frequencies of the signal.

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  But if you only have a DC circuit, that is, with no changing/varying voltage,
  or if you have a circuit with AC signals but only have resistance components,
        that is you have no inductors or capacitors,
  then Impedance equals Resistance.

• But Impedance becomes different from Resistance whenever you have inductors or capacitors in an AC circuit.
  Pure resistive components don't care about AC signal frequency. Their resistance doesn't change with frequency.
  But inductors and capacitors impede AC current flow due to their property called Reactance (X).
  And the magnitude/value of Reactance (X) from an inductor or capacitor is different depending on the frequency of the AC signal going through them.

• Impedance is calculated by combining regular DC resistance (R),
  plus a contribution from Reactance (X).
  There are a lot of ways/formulas that can be used to calculate Impedance, but here's the one using algebra:
        Z = √(R² + X²)
• Remember that, since Reactance of the inductors and capacitors in your circuit changes when frequency changes, Impedance is also different at different frequencies.
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• So now the basic definitions are taken care of, what's really going on?
  Impedance-3: Reactance

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