I presume this has built noise suppression via the coil or ferrite core on the wire.
Most commonal garden USB extensions available do not have this suppression, could one presume the coil or core is not a requirement, but that Sonofff are guiding their customers with this type of cable to have the best signal strength without interference from the cable.
Where Suppression is not provided on the cable, presume a USB 3.0 cable would be the next best choice - as these are better sheilded ??
Alternatively you could retro fit one:
No. You are not understanding noise or what the ferrite core provides.
You mostly see ferrite cores on power cords because switching power supplies can radiate RF energy that can cause issues with other equipment. A ferrite core on a USB cable is for suppressing spurious RF from USB power sources, like cheap USB power supplies.
I haven’t seen any shielded USB cables. Not saying that there aren’t any, but in my lab (what my wife calls my workshop) I have cut several USB cords to solder into a project, and I have never encountered a shielded USB cable. (But I tend to buy really cheap USB cables for those projects).
Zigbee dongles are recommended to be physically away from the computer it is plugged into because the computer itself generates a lot of RF noise that can degrade Zigbee performance. Of the three common protocols, WiFi, Z-Wave and Zigbee, Zigbee operates at the lowest power. This means that the signals the Zigbee receiver is expecting will be quite weak. Any extraneous signals in the same frequency band, including WiFi or noise from the computer, can overwhelm the Zigbee receiver. The interfering signal doesn’t have to be on the same frequency (I.E. channel), just on the same frequency band.
USB2.0 to the dongle is recommended because the harmonics of the high-speed data of USB3.0 will raise the noise floor at the 2.4 GHz band. Again, like the noise from the computer, only the stronger Zigbee signals will be heard by the Zigbee receiver.
