metal spiral cable compression protector effect on grounding USB? - Page 1
Forum section: electronics / rf-microwave

author: coppercone2
author_rank: Super Contributor
timestamp: October 05, 2018, 07:46:43 pm
content: I was in the store and i saw some USB cables today. There was a kind sold with a metal coil around it for compression strength I guess.The cable looked like it was made with conductors/dual shield/nylon fiber/metal coil shield with significant spacingI was not sure if the coil is connected to ground or floating, but the connectors looked to be made of metal.So the shield is separated from the mechanical coil by the nylon mesh. I could not tell if the coil was grounded or floating.I needed a USB cable but I ended up getting the Kevlar-reinforced one.The cable is Hama brand.How do you consider the circuit formed by the coil thats shorted out by the shield? I imagine the inductor having magnetic pick up, but its decoupling to the shield would depend on the thickness of the nylon.I would not be worried about it if it was floating, but I am curious about the circuit thats formed if its not floating, especially at high frequencies.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: October 06, 2018, 06:09:20 am
content: I have one of those hama USB cables, and I love them. I don't think the coil does much in terms of electrical performance, and that is also not why it is there. It is a nice cable, it feels very flexible but at the same time the shield prevents over-bending and it getting into a knot. Supposedly it should also make it less sensitive to being pinched or such. It's a similar technique used on a lot of very high end VNA cables, though usually you can't tell because they have layers above the spiraling steel strip. Here is an example of it where it is visible:https://www.pasternack.com/pages/Featured_Products/flexible-armored-test-cables-up-to-20-ghz.htmlMost high-quality cables already have multiple levels of shielding internally. I also have an image here from the H+S catalog that shows how there are multiple layers of shield (in this case two, a tape and a braid, but I've seen more).

author: coppercone2
author_rank: Super Contributor
timestamp: October 06, 2018, 03:16:37 pm
content: do you know if the steel spiral reinforced one also has kevlar threads in it?Your right, now i recall that VNA cables do have that shower look to them sometimes. I never saw it before though, only in BX or whatever cable.I figured unless I am around a rolling chair I don't really need the crush protection anyway.. It's more that I yank on the cable. My high end VNAish cables unfortunately do not have the spiral in them.The HAMA cable certainly does make normal computer cables look like shit though.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: October 07, 2018, 02:02:12 pm
content: Quote from: coppercone2 on October 06, 2018, 03:16:37 pmIt's kinda like seatbelts, I guess. 'Unless I am going about crashing my car I won't need them anyways'. You don't need it untill you do.Besides, in the case of VNA cables, it also helps enforce minimum bend radii, and ensuring that the actual center coaxial cable is subjected to almost no force, to make it as phase- and amplitude-stable as possible. Similar to the ruggedized VNA ports, where you first connect the actual RF coaxial connector (be it 3.5, 2.92, 1.8, 1 mm) and then have a massive outer threaded connector you tighten, which actually takes over mechanical.And the HAMA cable is a delight to work with. The metal spiral actually makes it very nice to bend, as it becomes stiffer as you bend it further, giving it a very nice behavior towards bending.

author: Lord of nothing
author_rank: Super Contributor
timestamp: October 08, 2018, 02:15:21 am
content: Maybe the are just for show?I like the Delock Cable. The are damn cheap and good quality.

author: coppercone2
author_rank: Super Contributor
timestamp: October 08, 2018, 02:37:55 am
content: but how is the pure electrical behavior, even if the effect is under noise floor under reasonable power levels?