Concepts of certain basic "Antenna Traps" in 5 Parts:

An "Antenna Trap" is simply a Resonant Circuit used to block certain frequencies

  • Looking at both Inductive and Capacitive effects in any kind of circuit.
  • Think of an Inductor as first a long coil of wire that actually interacts with each turn to effectively behave longer than if the wire was stretched out, and think of a Capacitor as just the opposite of an Inductor, therefore shortening the length of wire.
  • A "Series Resonant Circuit" behaves much like a simple short circuit at resonance,
    and a "Parallel Resonant Circuit" behaves much like an open circuit at resonance.
  • Bandpass Filters and Bandpass Reject Filters:
  • A "Parallel Resonant Circuit" may be used as a series element of an antenna, to behave as a High Impedance (i.e. an open circuit) to frequencies beyond the desired. An example given here for a Multi-Band Vertical Antenna:

    Inductors do not like Current Changes

    Capacitors do not like Voltage Changes