Test RG 11 Cable

First check with DC ohms meter that the outer and inner conductors are good. Try wiggling about a bit in case of intermittent connection. The inner to outer should be open circuit. Look out for spurious tiny fragments of braid/sheath wire if shorted.

For the frequency range you are interested in find some suitable signal source and a corresponding measuring device.
Connect together with short known good cable and record the result.

Insert the cable under test between the signal source and measuring device and measure again. The difference will be the cable loss. Compare with the manufacturer specification.

SAFETY: If you are using a spectrum analyser as the measuring device, check for NO DC power on the cable, or use a DC block permanently on the spectrum analyser input.

Example: The cable is used to connect LNB to indoor equipment.
Connect the LNB output to spectrum analyser using using a DC block if necessary, with a very short (known good) cable. Record the LNB noise across the spectrum and any signals from DC to 2.5 GHz. Repeat with the cable under test and observe the difference.

Regarding N type connectors: Note there are two types, 50 ohm and 75 ohm.  RG11 cable is normally 75ohm.  The 75 ohm male plug has a thinner centre pin that may intermittently connect, or not connect at all, if inserted into a 50 ohm female socket. If you have 75ohm male connector on the cable output it won't connect properly into a typical 50ohm spectrum analyser input socket.