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Re: [RFI] USB qrm - what to do?

To: rfi@contesting.com
Subject: Re: [RFI] USB qrm - what to do?
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Mon, 13 Mar 2017 15:15:28 -0700
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
On Mon,3/13/2017 2:34 PM, Steve wrote:
Do common, run-of-the-mill USB cables have shields? The USB page on wikipedia says a shield for the data pair is part of the USB specification. Just wondering if cheaper cables omit the shield?
That's hard to know without cutting one open. :)  Unbalanced audio 
cables SHOULD be shielded, but I remember seeing cheapies where the 
"shield" was a wire, or was a spiral shield (not very good for RF).
This falls under the heading of trying to identify the better quality 
products, which usually means NOT buying the cheapest. :)
I see on various web sites that some USB cables are advertised as 
having a shield, it seems that web pages for most cables do reference 
a shield. So if you want a cable with a shield, do you need to look 
for those cables that specifically state that they have a shield?
Dunno. See above.

One more question: If a USB cable has a shield, to what is the shield 
connected? Perhaps the USB connector's outer metal shell? On both ends 
of the cable? 
Yes and yes.

73, Jim K9YC

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