How to measure eletric wavelength of rf cable

[chinna_swamy7]

HELLO
WOULD YOU PLEASE SUGGEST ME TO MEASURE ELECTRIC WAVELENGTH OF THE RF CABLE.
HERE THE FREQUENCY IS 1.532GHz.
I HAVE A NETWORK ANALYZER (R&S).

 

[Antenna_Guy]

The velocity of propagation is c/sqrt(Er) where c is the speed of light and Er is the dielectric constant of the spacer.

Wavelength = Lambda = c/frequency (in free space) wavlength is reduced by sqrt(Er) in a cable

So assuming a dielectric constant of 2.2, the wavelength is

c / (frequency * sqrt(2.2))

 

[biff44]

I do not specifically know how to do it on an R&S, but if it is laid out like an hp:

Set frequency to run from 1.4 to 1.7 GHz
Calibrate for s21 measurement
hook up cable as dut
move cursor to your frequency of interst
then:

If it is a short cable (<one λ) just read off angle of s21. If it says something like 200 degrees and the cable is 1" long....your wavelength is obviously
1" *(360/200).

If you have a long cable, and the s21 phase wraps around 2π a couple of times, it is a little trickier. You push a button labeled something like "group delay". Move the cursor to frequency of interes. You will read something like 20 nS. That is the time it takes RF to travel from one end of the cable to the other.
You use that to compute the effective dielectric constant of the cable.

(C/√εr) * t = L

Once you know εr, use previous poster's equations.

 

[chinna_swamy7]

thanks friend
let me try with your valuable information.