I have a roll of old coax I've used for making assorted cables. Recently, I've had a couple of short cables (used for DC control applications) that show resistances on the order of 100kohms between centre conductor and shield, low enough to upset the operation of the equipment with which they were used.
Taking a careful look at this I notice this old cable is marked "ITT SURPRENANT DIV RG-174/U L.N.". I take it that the "L.N." must mean I've stumbled across the sort of low noise coax used with accelerometers and the like. It would seem that the process of soldering connectors to the cable, or this plus the application of a DC voltage to the cable for some time, is causing the dielectric to become conductive on occasion. Other cables I have made up from the same RG-174/U are fine, however. Cutting the connector off the cable appears to restore a >20 Mohm resistance, too.
Is anyone familiar with this sort of cable (this one has a uniformly black dielectric) ? Any ideas as to what might be going on and how I could avoid the low-resistance problem ? (other than buying some new, normal cable....I have lots of the old stuff I would like to use up)