I had a bit of bad coax on the most recent POTA, so I set out to test and repair it. I saw no damage to the cable or connectors, but there wasn’t continuity across the middle wire.
Which end is likely bad? I connected each end to the nanovna with a Smith Chart. I found on one end, the smith chart traced a spiral around the outside of the circle. The other side did not react at all, like I hadn’t connected anything. For comparison, I tried another cable I figured was good. That other cable had continuity to each end, and both ends each traced a spiral on the smith chart. The length of the spiral seemed to be related directly to the length of the coax: shorter traced shorter and longer traced longer.
So with that, I replaced the one end that didn’t react, and now the cable looks good.