The electrical length of a transmission line is dependant on 2 things...
1 ... the velocity factor of the line and
2 ... the frequency
an example ... to find the electrical length of a transmission line or dipole antenna
say for 400MHz
(300 million metres / sec (300,000 km / sec))
300 / 400MHz = 0.75m or 75cm that is the wavelength
now if we want an electrical wavelength in a transmission line that has a VF (velocity Factor) of 0.85 then....
75 x 0.85 = 63.75 cm so you can see that the electrical wavelength is shorter
than the free space wavelength
Dave
Dave