Stub tuners are used in RF systems to match impedances using precise lengths of transmission line that act as reactive elements (like capacitors or inductors). They can be either shorted or open at the far end.

This calculator estimates the **physical length** of a stub (in feet and meters) based on the operating frequency, the velocity factor of the cable, and the desired electrical length as a fraction of a wavelength.

The formula used is: \[ \text{Length} = \frac{300}{f} \times \text{Fraction} \times \text{VF} \] Where:

• f = Frequency (MHz)
• Fraction = Desired electrical length (e.g. 0.25 for quarter wave)
• VF = Velocity Factor of the coax

Use this to calculate line stubs for impedance matching, phasing, or notch filters.