And well, besides verifying that the cable/shield isn't damaged or broken, we can't really do anything without a LCR meter or other professional engineering equipment. Quality of cables depend on characteristic impedance which is hard to measure properly on some cable stuck in a wall, even if you have access to proper engineering tools.

Measuring total resistance of the shield with an ohm meter isn't a bad idea though - poorly connected shields can be the culprit.

So I actually know that resistance is a factor here. I actually have a tool that detects shorts based on resistance (in addition to a plain multimeter). However I don't know how many ohms it's supposed to be, and whether that's ohms per feet or if longer cables should be more conductive.

I also saw people mention impedance, but I don't get how that's relevant when there's no AC carried on a coax.

When you say LCR meter, the LC are capacitance and inductance. Why do those matter here?

But generally, yes, I am aware that the answer comes down to measuring some electrical properties of the cable :) An answer that explains what ranges exactly constitute "good" measurements would be great.

matthewsnyder‭ Resistance is not so much a factor. You can measure it, sure, but with a decent multi-meter you would get <1ohm both on the signal and the shield and that's it. But that only means that the cable isn't complete crap, not necessarily that it is suitable. The most important aspect here is if you are having signal losses, standing waves/energy reflections caused by poor impedance matching. The characteristic impedance of these should be 50ohm and measuring it isn't a layman's task. I left an answer on the EE meta.