100 m (328 ft) を超える長さリミット - CableIQ
CableIQ is testing per the Network requirements and not the cabling standards. When looking at the length of the link, the real issue is Insertion Loss, Propagation Delay and Delay Skew, which are all length dependent parameters. So long as these parameters are met, the length can be over 100 m (328 ft).
What about our other cable testers that use 100 m (328 ft). These testers are also correct, since they are testing to a cabling standard, not an application.
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In this example, we see the limit is 133.4 m. This is calculated from the reported length and the measured propagation delay. Although not shown, the propagation delay measured was 444 ns. That means it takes the signal on this link 1 ns to travel 0.234 m. The standard does not permit the propagation delay to exceed 570 ns. To calculate the maximum possible length using this cable link; 570 x 0.234 = 133.4 m. We still test for Insertion Loss of course, which will probably fail before the theoretical 133.4 m limit is reached. |
