[SI-LIST] Re: Floating Cable Shield
- From: Ivor Bowden <ivorlist@xxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Wed, 11 Oct 2006 11:45:19 -0700
Yes Mike, that is pretty much it exactly. The mfg link to this cable is:
http://www.vantecusa.com/product-accessory.html#
click on
Rounded Cable -> IDE
you can see an image. The cable I have is the clear one with the silver
braid. The images aren't that big, but you can get an idea.
I'm now thinking that maybe the braid is not intended for shielding
specifically, but rather as a physical support, or just for looks.
The question still remains, though, how would this configuration affect
SI and EMC - for better or worse?
When I specify cable shielding I always ensure that it is contiguous,
preferably enclosing the connectors at both ends. I would not specify
floating or single ended shielding. I wonder if there are cases, in
which such configurations could be useful?
thanks,
Ivor
on 10/11/2006 9:09 AM PDT Mike Haff wrote:
> What it sounds like Ivor is describing is an IDE cable that is the
> "round to flat" version. These came onto the market prior to SATA and
> were designed to improve the airflow within a system. If someone were
> to place a braided shield over the "round" sections between the IDC
> connectors you would have exactly what Ivor is describing. I'm certain
> there is heat shrink over the braided sections.
>
> I see no value what so ever with such a shield from either an EMI or SI
> standpoint. Sounds to me like a marketing gimmick (shielded IDE cable
> included!!!) gone bad.
>
> Mike Haff
> Engineering Manager
> Bay Associates
> 150 Jefferson Dr.
> Menlo Park, CA 94025
> 650-847-3954 direct
> 800-522-0661 main
> 650-327-4171 fax
>
> -----Original Message-----
> From: Shawn Nikoukary [mailto:shawnn@xxxxxxxxxxx]
> Sent: Wednesday, October 11, 2006 8:39 AM
> To: ivorlist@xxxxxxxxxxx; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Floating Cable Shield
>
>
> Hello Ivor,
>
> Is it possible for you to send us a pic or the link of manufacturer for
> this cable? I am curious to see how it looks.
>
> Regards,
>
> Shawn Nikoukary Cadence Design Systems
> Sales Technical Lead 2655 Seely Ave, MS 9B2 =20
> Silicon Package Board Division San Jose, CA 95134 =20
> Office (408) 944-7328 Cell (408) 712-1073 =20
> Email: shawnn@xxxxxxxxxxx Fax (408) 944-7772
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Ivor Bowden
> Sent: Wednesday, October 11, 2006 8:29 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Floating Cable Shield
>
> Hi,
>
> I ran into what I thought was an interesting cable and am looking for=20
> comments. This is an IDE cable on a new PC I got. The construction is=20
> twisted pair ribbon cable (flat spots for IDCs between the twisted=20
> sections), about 20" long, IDC both ends, a 3rd IDC about 7" from one=20
> end. What makes the cable interesting to me is there are two braided=20
> shields covering the bundled twisted pair sections, one about 8", the=20
> other about 3.5". These shields have no connections, not to a drain=20
> wire, not to each other and to to any circuit or frame ground, they
> are=20 entirely floating. My question is, how effective is this type
> of=20 "floating" shield, in terms of SI and EMI?
>
> This also brings up the general question of cable shield termination,=20
> circuit/chassis ground at both ends v.s. one end only v.s. floating;=20
> what characteristics to expect in each case?
>
> And that brings up the specific question of shield return treatment
> in=20 the connector area, single drain wire v.s. complete enclosure?
>
> Thanks,
>
> Ivor Bowden
> Hardware Engineer
> Curtiss-Wright Controls Embedded Computing
> Video and Graphics
> San Diego, CA 92121
>
>
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