[Uram-rejections] Twisted pair

Tue Jun 21 07:54:29 BST 2016

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 last sentence is a bit disrespectful 

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> From webstump at chiark.greenend.org.uk Tue Jun 21 04:11:32 2016
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> From: Jerry Stuckle <jstucklex at attglobal.net>
> Newsgroups: uk.radio.amateur.moderated
> Subject: Re: Twisted pair
> Date: Mon, 20 Jun 2016 23:11:19 -0400
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> On 6/20/2016 5:52 PM, mm0fmf wrote:
> > On 20/06/2016 22:15, Jerry Stuckle wrote:
> >> On 6/20/2016 1:31 PM, mm0fmf wrote:
> >>> On 19/06/2016 21:30, Roger Hayter wrote:
> >>>> mm0fmf <none at invalid.com> wrote:
> >>>>
> >>>>> On 19/06/2016 15:37, Jerry Stuckle wrote:
> >>>>>> On 6/19/2016 8:38 AM, mm0fmf wrote:
> >>>>>>> On 19/06/2016 11:50, Roger Hayter wrote:
> >>>>>>>> being a digital system
> >>>>>>>
> >>>>>>> At the level being discussed it's an analog system. Very fast I
> >>>>>>> grant
> >>>>>>> you but the signals on the wires are not digital.
> >>>>>>>
> >>>>>>>
> >>>>>>
> >>>>>> Actually, ethernet is a digital system.  The signal is two levels
> >>>>>> - on
> >>>>>> and off.  Yes, there is some distortion of the signal while
> >>>>>> traveling,
> >>>>>> but it is still a digital signal.
> >>>>>>
> >>>>> Shame I happen to work for someone who just happens to make Ethernet
> >>>>> PHYs. It's analog at the cable, we employ analog mixed-signal
> >>>>> designers
> >>>>> to develop the insides of PHYs. Elsewhere, when you look at the
> >>>>> signals
> >>>>> passing from the PHY to the MAC and signals from the MAC, they're
> >>>>> digital. Designers just specify whatever standard pin driver is need
> >>>>> from the libraries. But not the cable/PHY.
> >>>>
> >>>> There is no actual distinction between a digital and an analogue
> >>>> signal,
> >>>> the physics is the same.  But when it takes some effort to recover the
> >>>> data intact then analogue design skills certainly come into it.   But
> >>>> you are also correct (looked this up) that there are *not* just two
> >>>> binary levels but five of them in in gigabit ethernet.  Note, five
> >>>> discrete levels, *not* a continuous range of desired values.   And all
> >>>> four pairs in the standard cable are used.  10Gb is something else
> >>>> again.   But it is still a digital signal, just one that needs lots of
> >>>> analogue style care and attention to recover intact.
> >>>>
> >>>>
> >>> Yes Roger. It's not OOK at the high rates and is multi-level.
> >>
> >> Roger is true - at 1GB and above, there are multiple levels involved.
> >> However, these are *discreet levels*.  The signal is still considered
> >> digital.
> >>
> > But hang on Jerry I thought an ethernet signal on a cable has one of two
> > valid values - on or off, one or zero. Now you are saying it's multiple
> > discreet levels.
> >
> 
> It depends on the speed of the ethernet.  Different speeds use different
> encoding methods.  As I said 0- *1GB and above*...  Do you read what you
> reply to?
> 
> > What is being missed is not whether Ethernet is digital, it is, but the
> > front end of the PHY is a very analog thing and not like the inputs of
> > typical logic systems.
> 
> No, the front end is digital, also.  It may use some analog techniques
> to process the signal - but it is still considered a digital signal and
> a digital front end.
> 
> You really need to take some EE courses and learn about both analog and
> digital signal processing.
> 
> -- 
> ==================
> Remove the "x" from my email address
> Jerry, AI0K
> jstucklex at attglobal.net
> ==================
> 
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