Is there an industry standard measure for coaxial cable stiffness? By stiffness I mean the spring force experienced when bending or deforming the cable.
In my search for a highly flexible lab test cable, I've been unable to find a standard measure of coaxial cable stiffness. All the manufacturers give minimum bend radius numbers, but there doesn't seem to be any industry standard way of denoting cable stiffness.
There are in fact some very low stiffness cables available. You can hold them in your hand and the protruding part of the cable will hang loosely over your hand.
They are typically very expensive, but provide high phase stability, and are often used in test labs (for example when using a network analyzer).
Unfortunately I don't know of any standardized way of spec'ing these cables. The best way to choose them might be to get a salesperson to bring you a sample to look at.
One example is the Megaphase VN series, but other high-end cable manufacturers have similar products.
The nature of Coaxial cables is that they are all stiff. The intention is to maintain the spacing between the core and the screen so the permeability stays the the same. This means the geometry of a cable should stay the same along it's entire length.
Those that flex or have been bent are now no longer perfect. For most applications this perfection might be desirable but is not required.
In a production test environment the length of the cable (connecting instruments) are usually determined by where and how the equipment will be tested.
So the advice is either lay the equipment (to be connected) out with plenty of clear space to allow everything to "float" in to position that doesn't stress anything to much or make cables the right length for the task.
The OP's task of finding flexible cable will be as hard as user6972 said and would be a waste of time unless absolutely necessary.
