Reward for lost Kraken!
Join Date: Apr 2006
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K1, coax is mainly plastic and if it was rigid--you couldn't bend or coil it. It is designed to be yielding, and the "better" insulators tend to have more air and less plastic in them, making them even weaker.
I think every cable maker, and the ARRL and the other radio organizations, all say that coax must be supported or it will "go taffy" and pull out on itself. For you to call that a MYTH and a lie, just because you haven't noticed a problem with the particular coax you use, is a bit rash. Sure, they could all be lying. But first try this: Buy 100' of premium coax with an airy insulator and thin center conductor. 1/4" stuff like most boaters use, not RG8. Lay it out, use a steel tape to measure and mark two poins 100' apart on it.
Now suspend the top end from something and let it hang unsupported for a year. then lower it, and measure the distance between those two marks once again. THAT will be lab science. And, I'll bet that those 100' marks will be more than 100' apart.