Plain-language answer: Velocity factor is the speed of a signal in a transmission line divided by the speed of light. It makes electrical wavelength shorter than free-space wavelength.
Why it matters at the radio
Cable dielectric and construction determine the value. It matters when a line is cut as a phase section, impedance transformer, stub, or accurately modeled feed system.
What to watch in the field
Use the exact manufacturer value as a starting point and measure the finished cable when phase or electrical length matters.
The common misunderstanding
Applying coax velocity factor to a bare wire antenna—or one cable’s value to every cable.
Learning boundary
This lesson explains established radio and antenna practice. Current regulations and the exact equipment or antenna guide control legal limits, ratings, compatibility, and safety.
