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We have been having problems with pre-made BNC cables. The cause has been narrowed down to the fact that once the BNC is locked in place the cable can still rotate relative to the connector. This can result in the soldered core, or the shield, or both tearing free. The symptoms are a full or partial loss of signal or a major increase in noise.

The question being - how can I specify that the body of the cable is molded to the plug so that this problem is eliminated? I have found a suitable such cable, but as often happens it is apparently going out of production. Any suggestions?

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  • \$\begingroup\$ Move to a different connector style. A BNC cable always rotates. \$\endgroup\$ – vini_i Sep 3 at 17:07
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    \$\begingroup\$ BNC cables are supposed to rotate relative to the knurled outer shell. If rotating the cable causes the pin to break or the shielding to break or come out of the crimp, then there's something wrong. Even the best cable will wear out, though. I've assembled approximately 5 bazzillion of them. One task at my first real job was making BNC cables for the test rigs in the factory. The main job was building radios in the factory, but cables don't make themselves. \$\endgroup\$ – JRE Sep 3 at 17:42
  • \$\begingroup\$ I suggest that you should discuss this problem with your cable supplier. I've made and used many BNC cables and don't recall having the problems you mention (other than a couple where I used the wrong crimp tool on the shield). \$\endgroup\$ – Peter Bennett Sep 3 at 17:46
  • \$\begingroup\$ @vini_i The Teishin cables do not rotate relative to the locked BNC. I am not talking about the end piece that is designed to rotate. I am talking about the cable rotating when twisted when the BNC is fully mated and the metal pieces are static with respect to each other \$\endgroup\$ – Dirk Bruere Sep 4 at 10:10
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    \$\begingroup\$ Right. They all do that. The inner part of the connector, the pin, and the cable should all move together. \$\endgroup\$ – JRE Sep 4 at 10:48
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If it pays off, a TDR test for cable quality can be a clear solution.

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  • \$\begingroup\$ That is not going to help. It is obvious to see when a cable is working, or the cable is broken when we manufacture a machine. It gets broken after shipping, presumably because it gets twisted on the customer site during the installation process.. Only some cables are prone to this. \$\endgroup\$ – Dirk Bruere Sep 4 at 10:17

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