On Wed, 24 Jun 2020 07:00:45 +0100
The Natural Philosopher  wrote:

>On 23/06/2020 22:22, David Higton wrote:
>> In message 
>>            Michael J. Mahon  wrote:
>>
>>> More likely, capacitance between lines of a longer cable slows signal
>>> transitions, eroding signal margins.
>>
>> Please, learn transmission line theory.
>>
>> David
>>
>Is there any evidence that a USB cable behaves as a transmission line?
>Or that the spec matches source and destination impedance to it?
>
>Hmm it seems they do
>
>https://electronics.stackexchange.com/questions/325721/do-usb-data-wires-d-d-h
ave-90-ohm-differential-impedance-and-single-ended-45
>
>There will still be attenuation however over longer cables

I would have been very surprised if the spec wasn't for transmission line
behaviour - it's not exactly a new concept. Cheap Chinese cables however...


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W J G

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