Antenna Trap Design Calculator

Calculate trap capacitor and inductor values for multi-band wire antennas. Includes coil winding data and impedance analysis.

Trap Frequency

MHz

Coil Inductance

μH

Coil Form Diameter

Tab to move between fields

Required Capacitance

50.6 pF

Trap Impedance (Q=200)

44,454 Ω

Coil Turns

7.6

Inductive Reactance222.27 Ω

Capacitive Reactance222.27 Ω

Wire Length for Coil5 ft

Turn Spacing0.328 in

Trap Bandwidth (3 dB)0.071 MHz

How to Use This Calculator

Enter the trap resonant frequency (MHz) matching the band you want to isolate.
Set the coil inductance (µH) and coil form diameter (mm) for your wound coil.
Review required capacitance (pF), inductive reactance (Ω), and number of coil turns needed.
Use the trap impedance output to verify the trap will effectively isolate the outer section.
Wind the coil to the calculated turns and trim the capacitor to achieve resonance.

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Formula

C = 1 / ((2πf)² × L); Turns via Wheeler's formula

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