Selecting SVGA cable
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From: Ian D on 22 Nov 2009 19:01 "JimL" <invalid(a)invalid.inv> wrote in message news:he9lmq$p6k$1(a)news.eternal-september.org... > "VanguardLH" <V(a)nguard.LH> wrote in message > news:he4pqf$gs7$1(a)news.albasani.net... >> JimL wrote: >> >>> "Pen" <nospam(a)nospam.net> wrote in message >>> news:he4lu5$a50$1(a)news.eternal-september.org... >>>> JimL wrote: >>>>> I'm looking at SVGA cable for an extension monitor. They show two >>>>> similar cables, the only difference, including price, is that one has >>>>> a >>>>> ferrite beads, apparently at each end, and one doesn't. Why would I >>>>> want >>>>> ferrite beads or not want ferrite beads? >>>>> >>>>> Thanks >>>>> >>>> To prevent which would interference on your screen also to improve the >>>> quality of the transmitted signal from the computer to your screen. >>>> I would say get the one with the beads. >>> >>> I'm very curious about my second question. Why would I want a cable >>> without >>> the beads? That's another way of saying "why do they sell cables >>> without >>> the beads? And for the same price?" >> >> Cheaper quality doesn't always equate to cheaper price. >> >> Some cables have better shielding so using the beads to induce a reverse >> signal to provide impedance to higher-frequency noise isn't needed >> (because the noise didn't get induced into the signal wires inside the >> better shielded cable in the first place). Better shielding tends to >> make the cable stiffer. Ferrite beads allow use of a more flexible >> cable because of less effective shielding. Ferrite beads are cheaper >> than adding better shielding to the cable. >> >> http://en.wikipedia.org/wiki/Ferrite_bead >> >> With the 2 cables being the same price, I doubt the non-beaded cable has >> adequate shielding. Heavy shielding costs a lot more than a couple >> ferrite donuts on the ends. So get the beaded cable. > > > Thanks > > -- > For most of us the most danger is most politicians. > > JimL > > The ferrite bead has nothing to do with with shielding. The purpose is to suppress common mode high frequency noise that can be present, even on the outer shield. Part of the bead's purpose is to suppress radio frequency emissions from the cable, that could interfere with other electronic devices. You can find the beads on higher quality, and some lower quality peripherals, although higher quality components are more likely to have the beads. The beads are usually applied to USB, power brick, and VGA and DVI video cables that are packaged with peripherals. Network cables don't need ferrite beads, because of the way the cable pairs are twisted in alternate signal pairs, in order to cancel any RF emissions, or pickup. |