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Re: [RFI] USB Cable Shield Resistance was: Re: [N1MM+] open question abo

To: "Jeff (W4DD)" <w4dd09@gmail.com>
Subject: Re: [RFI] USB Cable Shield Resistance was: Re: [N1MM+] open question about RFI & USB
From: Pete Smith N4ZR <pete.n4zr@gmail.com>
Date: Tue, 16 Jan 2024 15:34:04 -0500
List-post: <mailto:rfi@contesting.com>
Not on mine, Jeff - all plastic.


73, Pete N4ZR

On 1/16/2024 12:04 PM, Jeff (W4DD) wrote:
No pin is needed.  There is a metal shell around the RJ45.

On Tue, Jan 16, 2024, 11:40 AM Pete Smith N4ZR <pete.n4zr@gmail.com> wrote:

    Oh Joy - another thing to check.  I'm using a plain Ethernet Cat 5
    patch cable from my amp to my computer.  Judging by how floppy it
    is, I suspect no shielding at all - but a question - if there were
    a shield, which pin on the Ethernet connector would it be?

    73, Pete N4ZR

    On 1/16/2024 10:22 AM, Jeff (W4DD) wrote:
    Pete, just another data point based on my experience with shielded Ethernet 
cables.  Excerpt from one of my PPT's follows.  I found the shield connections 
to be intermittent.



    Do Not Use Shielded Ethernet Cables from the Common Internet Sites
    The shield is not soldered to the metal RJ-45 shell.  I measured 2-20 ohms 
on a group of 5 jumper cables shell to shell.  Mouser Electronics has Amphenol 
Ethernet cables ($7) with the drain wire soldered to the metal RJ-45 shell at 
both ends.  Resistance was less than 1 ohm for each of 5 cables measured (view 
the spec sheet at Mouser.com).

    Jeff, W4DD

    -----Original Message-----
    From: RFI<rfi-bounces+w4dd09=gmail.com@contesting.com>  
<mailto:rfi-bounces+w4dd09=gmail.com@contesting.com>  On Behalf Of Pete Smith N4ZR
    Sent: Tuesday, January 16, 2024 9:32 AM
    To:N1MMLoggerPlus@groups.io; RFI List<rfi@contesting.com>  
<mailto:rfi@contesting.com>
    Subject: [RFI] USB Cable Shield Resistance was: Re: [N1MM+] open question about 
RFI & USB

    Interestingly, I just tested the shielding on a USB A to USB C cable I 
have, which looked like it should be fine, with a transparent jacket over woven 
shielding and a big ferrite bead - about 1 meter long, and measured 2.7 ohms - 
not good.  What should be consider to be the upper permissible shield 
resistance?

    Moving this issue to the RFI reflector now...

    73, Pete N4ZR

    On 1/16/2024 5:01 AM, Janez Majdic viagroups.io  <http://groups.io>  wrote:
    Maybe also good to read:
    https://www.yoctopuce.com/EN/article/usb-cables-shielding-matters-as-w
    ell

    Regards, Janez - S51J
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