Cable length measurement to check the velocity factor. The RF signal from the transmitter comes from the left, and the electrical length of the cable (cyan) is determined by measuring the signal delay between ch1 (red) and ch2 (yellow).
This is when both ch1 and ch2 probes are at the dummy load. The frequency of the RF signal is 7.026MHz, and there is no delay between the two channels.
This is when the ch1 probe is moved to the left end of the cable under test (cyan) as is shown in the first figure.
The delay of 11.40nS is observed.
The RF signal is now QSYed to 14.052MHz. Of course, the delay is the same whatever the frequency is.
This is with another cable with the same specifications. The delay is now 11.60nS.
Since the delay of 1nS corresponds to the 0.3m of the electrical length, the length of the cable is 3.42m. Since the physical length of the cable is 2.0m, the velocity factor becomes 0.58, which is somewhat different from the the velocity factor of 0.67 of RG-58U cables.