How do I determine extension factors for unknown cables with the Metracable TDR PRO?

The instructions on myGMC describe how to determine the unknown extension factors of a cable using a reference cable of known length (penultimate page above).

Please also note the following points:

• The length of the connected test lead must be added to the known length of the reference cable. For longer cables, this may be negligible.
• To determine the length, place the cursor on the display at the beginning of the echo and not at the maximum.
• There is no minimum length of the cable to be tested, but the pulse width and the resulting dead zone must be taken into account. For a 25ns test pulse, the dead zone is approx. 6 m for a cable with a shortening factor of 0.8. Cables with cable lengths less than the dead zone can also be measured by using a feeder cable with the same properties as the cable to be tested and a length greater than the dead zone.
• The resolution that can be read on the display is also determined by the smallest cable length (pulse) to be set. For the smallest pulse width of 12ns, this is approximately 30cm, depending on the shortening factor.