Reducing Induction Effects, Counter-EMF, and Stray Voltages in Low-Voltage Communication Wires.

One of the observations which amaze older people like me, is how high the frequencies have become, at which even household appliances such as USB Cables can communicate. In my youth and young adulthood, such things would not have been considered possible. And the surprise which this progress brings, comes more strongly to older people, who actually did know about Electronics.

There is a basic enemy to allowing communication at high speeds: Plain wire has linear inductance, which becomes significant at the higher speeds.

There is a basic methodology to reducing the unwanted effect: Actual signal-wires are often accompanied by a shield wire, which needs to be grounded or connected to zero, at both ends of a wire bundle.

The concept is quite simple. This shield wire acts as a kind of secondary winding, to a virtual transformer, of which the signal wire would be the primary winding. Whatever counter-EMF the signal wire would produce, would also need to exist along the length of the shield wire. But because the shield wire is grounded at both ends, the counter-EMF which the signal wire can produce is also greatly reduced, in comparison with what one would obtain, if the signal wire existed by itself. When current flows in one direction through the signal-wire, current also flows in the opposite direction through the shield wire. If that current could not flow, then the full linear inductance of the signal wire would seem to exist. Otherwise, not so.

Now I suppose that it would be nice if overhead wires that stretch geographical distances, could also be shielded as easily. But one fact which is highly disappointing is, that shielding / elimination of stray-power problems, is highly lacking in many practical situations. More specifically, power lines may often only seem to have real phase wires, but no neutral wire that runs parallel. Instead, what some Engineers do, is simply to sink a grounding electrode into the earth, at the receiving end of such an arrangement.

The problem with that is the fact, that Earth is not a perfect conductor, and was also never ‘meant to’ participate in Humans’ high-voltage circuitry.

(Updated 3/12/2019, 15h20 … )

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Problems with my DSL, Recent Down-Time

I take the unusual approach of Hosting my site and blog on my private PC at home. This is not a recommendation for other people to do the same thing, it’s just how I do it. But then a side effect of what I do is the fact, that the availability of this blog is only as good, as the (DSL) network connection of my PC at home.

In recent weeks, Quebec, the province I live in, has been pounded by extremely cold weather (below -20⁰C), as well as more than one snow-storm. And this has played havoc with many customers’ service, as ice and water can penetrate the cables.

For that reason the availability of my site and blog has also experienced many issues. I apologize to my readers if this has inconvenienced them.

For the moment it looks like my ISP has been able to stabilize my connection, by reducing the speed with which I connect, and I’m fine with that, since a stable but slower connection is preferable to no connection at all.

I’m looking forward to some better solution in the distant future, but am confident that in the short term, the connection has been made stable again.

Dirk

 

My Experiences with the Bell Home Hub 3000

My ISP is Bell Canada, and my LAN connects to a service of theirs called ‘Fibe 50′, which stands for a 50 Mbps, DSL connection, to a Local Node, which in turn is connected to Bell via Fibre Optics. And this connection of my LAN is accomplished through a Home Hub 3000 Modem / Router.

The fact that I use my home PC as my Web-server, also means that a stable Internet connection is especially important to me, even though officially, I’m just a Home User. Just recently, my site experienced some down-time, due to problems with my DSL. And I’d like to weigh in on how good or bad the Home Hub 3000 might be, based on personal experiences.

First off, this Modem / Router once had a very bad reputation, when it was first released for public use, in the year 2016. But because that release of the modem preceded my personal range of experiences, I’m going to ignore this piece of History for the moment. It could very well be that in the year 2016 the modem was not ready to be released yet, but that in the year 2019, it is. This would be one example, where the service provider did their best to patch the behaviour of the modem, with many firmware updates, but without any actual modifications to the circuitry being possible.

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