KNOWN INDUCTANCE · CAPACITOR RANGE · RESONANCE
AM Antenna LC Tuning Calculator
Enter a measured or specified antenna inductance to find the capacitor value for your target frequency. Check the ideal tuning range of a variable capacitor, including other parallel capacitance.
Calculate AM antenna capacitance and tuning range
Live resultsMETHOD & ASSUMPTIONS
How antenna inductance and capacitance set resonance
Calculation method
The antenna inductance and total parallel capacitance form an ideal LC resonator. Stray capacitance is added to the variable capacitor value.
The maximum capacitor value gives the lower frequency endpoint; the minimum capacitor value gives the upper endpoint. The diagram shows ideal resonance across the entered capacitor range.
In the formula, L is in henries, C is in farads and f is in hertz. The calculator converts the entered µH, pF and kHz values automatically.
Scope of this estimate
Enter measured or otherwise specified antenna inductance. This tool does not calculate ferrite-rod inductance from rod dimensions or an air-core formula.
Receiver loading, coil self-capacitance, variable-capacitor tracking and frequency-dependent inductance can change actual tuning. Include known parallel capacitance in the stray-capacitance input and verify the assembled receiver.
WORKED EXAMPLE · NOT A PRODUCT SPECIFICATION
Example: 250 µH antenna tuned to 1000 kHz
A 250 µH antenna needs about 101.32 pF of total parallel capacitance for ideal resonance at 1000 kHz. With 15 pF of other parallel capacitance, the required variable capacitor setting is about 86.32 pF. A 20–365 pF variable capacitor gives an ideal range of approximately 516.37–1701.44 kHz. Verify the assembled receiver because loading and frequency-dependent coil behavior can shift the result.
BEFORE YOU SPECIFY
Common design questions
Can the tool calculate my ferrite rod’s inductance?
No. Supply a measured or specified inductance for the antenna. The tool calculates ideal LC tuning from that value.
What does “outside tuning range” mean?
The required variable capacitance is below your minimum or above your maximum. Change the inductance or capacitance range, then verify the assembled receiver.
Does the result predict reception distance?
No. It does not model receiver sensitivity, losses, loading, antenna orientation or the propagation environment.
FROM CALCULATION TO COIL