Stranded vs solid core coaxial cable

[matthuszagh]

What are the pros and cons of stranded- vs solid-core coaxial cable. I previously assumed that stranded-core cable would generally be higher quality than solid-core cable for two reasons: (1) more flexible, and (2) slightly higher conductivity at high frequencies. However, looking through Pasternack's catalog I've noticed that most of the high frequency and more expensive cables are solid, not stranded, core. Why is this?

If I were to hazard a guess as to why solid-core isn't a disadvantage in terms of flexibility it would be that other factors (such as dielectric material) dominate the flexibility. For example, I have 086 cable that is very flexible but also solid core. Does this mean that you'll damage other aspects of the cable (e.g., dielectric) before damaging the center conductor from bending? If this is correct, though, it still doesn't tell me why solid core is apparently better, just why it isn't worse than stranded-core.

So, does solid have advantages over stranded and, if so, what are they?

[bdunham7]

Solid core has lower losses and less handling noise, if that matters.  Many coax installations are fixed and do not require repeated flexibility, some even need stiffness.  Stranded cores are mostly for flexibility, like test leads or cables for equipment that moves around.

[matthuszagh]

Solid core has lower losses and less handling noise, if that matters.  Many coax installations are fixed and do not require repeated flexibility, some even need stiffness.  Stranded cores are mostly for flexibility, like test leads or cables for equipment that moves around.

Good to know about the lower loss, I wasn't aware of that. What is handling noise?

Is there a danger of repeated flexing (above the minimum bend radius) with solid core cable? It seems like some of these solid-core cables are designed undergo repeated flex despite the solid core (for example this flexible 086 cable from pasternack https://www.pasternack.com/precision-0.104-semirigid-replacement-50-ohm-coax-cable-fep-jacket-pe-p086-p.aspx).

[Bassman59]

Solid core has lower losses and less handling noise, if that matters.  Many coax installations are fixed and do not require repeated flexibility, some even need stiffness.  Stranded cores are mostly for flexibility, like test leads or cables for equipment that moves around.

Good to know about the lower loss, I wasn't aware of that. What is handling noise?

It's basically a piezeoelectric effect. As the cable is flexed it generates electrical noise. This is a real problem with stage microphone cables that feed high-gain preamps and then a big PA. The little noise gets amplified and is clearly audible. So a lot of effort has gone into designing cables that minimize this problem, and no decent cable exhibits the problem.

Good stage cables use stranded conductors and a braided shield. Some have a foil shield with a drain wire for easier assembly as the drain wire is what is soldered to the XLR connector's Pin 1. Braided shield is preferred because with enough flexing the foil breaks and is no longer a complete shield, even though the drain wire maintains the connection. For installation where the cable is not moved, cable with solid conductors and just the foil shield (again with drain wire so you can assemble it) is used. The installation wire has thinner outer cases than the thick rubber of a stage cable, so more of it can be fit into a wall or behind the console.

Is there a danger of repeated flexing (above the minimum bend radius) with solid core cable?

Oh, yeah! It breaks! The bend radius says "flexing this much means you're definitely breaking the cable." Flexing to a radius greater than the minimum doesn't mean it breaks immediately. Usually the cable manufacturer (if reputable, not the random Amazon seller) has flex data readily available.

[David Hess]

When using the proper connectors, I find solid and stranded cable equal to work with.

Stranded cable is more flexible making it more suitable for a test environment.

[bdunham7]

What is handling noise?

Handling noise is generated by the triboelectric effect, where when the internal conductors in the cable come into or lose contact with the insulator a small noise is generated.  The most widely known example is indeed the microphone cable and there are specific low handling noise cables made that mitigate this issue by using a conductive layer on the outside of the inner insulator and sometimes putting a graphite compound in the braided shield.  These cables are often designated as 'not for RF use'.  Belden 9223 is an example.

There are other systems that need a low-noise cable and similar techniques are used.  Solid core cable can be quite flexible in some cases and can work for test leads, although fine-stranded cores will always be more pliable all else being equal.  Here are some specialty cables for a non-audio use that come in both solid and stranded core.

https://www.pcb.com/sensors-for-test-measurement/cables/low-noise-coaxial