Quote Originally Posted by E-Stat
Obviously, that is incorrect given the presence of shielding in a wide range of cables. Here is one of the times I directed this question to you where you did not respond:

Sighted Testing IS King!! Silly me - all those years wasted...

So what is the missing metric? rw
Since I'm on a roll, here is something for you to read: http://www.floemc.com/applications/s...ness/index.jsp

In general, Belden doesn't give any shielding data because shielding effectiveness very much depends on the installation of the cable, the connectors, the length, the environment, the equipement connected, etc. It would be impossible for Belden to come up with data for all of the scenarios their customers use for their cabling. Shielding is not a cable metric, it is measure of protection for the signal in a given environment.

And actual shielding effectivene testing is quite complicated and expensive. When it does happen, it is usually tested for a specific purpose. For example, on our naval vessels, there are several high power emitters like radar, fire control radar, HF communications, etc. So we have done a thorough shielding effectiveness test (usually before a ship is first commissioned and then only infrequently after that) by simulating the actual shipboard radiation it will be exposed to and having all sensitive electronic equipment operational. This is a tedious and expensive process.

During the normal life of a ship, cables and equipment are designed to meet military standands with some manufacturer's testing. Mostly, equipment problems at sea are tackled with troubleshooting and if EMI is the culprit, then measures are taken to eliminate the problem.

I guess an analogy would be designing a skyscraper. You obviously need to consider hurricanes and earthquakes when you design the structure (thickness of steel, use of cement, flexibility points, etc.) but you don't actually do tests on a completed building.

Quote Originally Posted by E-Stat
As for pertinent facts, how does Motorola determine how much shielding is required for a given component? rw
Motorola would analyze the range of envirnments the product is expected to operate in and then apply current good engineering practices regarding shielding. They may even do some testing to verify that the shielding is adequate. Sometimes the customer has special requirements which it can identify and Motorola will provide custom shielding (at a higher cost of course).