70.7Ω coaxial cable is often used to build power splitters and Wilkinson combiners, it is used also as λ/4 matching between 50 and 100Ω.
To demonstrate the operation of the λ/4 transormer we have verified the correct impedance transformation between 50 and 100Ω at the frequency of 128 MHz.
Z = √50 x 100 = 70.7Ω
λ/4C = λ/4 x VF
λ/4C = Matching line 1/4 wavelength on cable
λ/4 = 1/4 wavelength at 128 MHz
VF = Velocity factor 70% (for PTFE is 0.70)
λ/4 = 300/128 x 1/4 = 590mm
λ/4C = 590 x 0.70 = 410mm (this is the real length of the cable)
The graph below shows the return loss or impedance matching at the frequency of 128 MHz, as you can see the result is very good.