Helical resonator filter calculator
Online helical resonator calculator — a two-section band-pass filter worked out from the passband to every dimension.
AWG to millimetres converter
Online AWG converter — wire gauge to diameter, cross-section and resistance, and back.
Coil self-capacitance calculator
Online self-capacitance calculator — C₀ and inductance by regression over a series of resonances.
SMD and capacitor marking calculator
Online marking decoder: SMD resistors (3-digit, 4-digit, R notation, EIA-96) and capacitors, both ways — code to value and back.
Air variable capacitor calculator
Online air variable capacitor calculator: capacitance from the plate geometry, breakdown voltage from the gap, and a reverse fit to a given capacitance and voltage.