On Thursday 12 December 2019 13:07:31 John Dammeyer wrote: > Way back in 2000 I was part of a company (nSine) in the UK. We > developed powerline networking and could actually send MPEG-4 video > over powerline. Unfortunately when the tech bubble burst so did the > company. I was chatting with the founder of the company a few weeks > ago and in hindsight we wish we'd concentrated a bit more on the > appliance side but the money was all for networking over powerline. > > The biggest problem was also lack of co-operation between competing > technology companies. Oh and as more and more switching type power > supplies were connected to the AC Mains the more electrical noise was > introduced. So the standards for emitted noise were very low and our > signals had to fit below that level. > > That's one place were government regulations could have really helped. > By setting 'accidental' emissions really low but allowing signal > emissions to be above that but still below some other level. > > The third and really most interesting problem was that even a > household power line is still a star based signal transmission line > with taps. Easier in the UK and Europe because of the 220VAC. More > difficult in the USA/CANADA because split phase 220VAC/110VAC. Even > X-10 has had problems with that. > > Anyway, as a transmission line it has reflections and null points at > high frequencies and it's pretty well impossible to add termination > like you would for an RF antenna or CAN bus network that requires 120 > ohm resistors at each end and cable with an effective impedance of 120 > Ohms. AC Power line also has a bandwidth of only 3MHz to 30MHz some > of which is in the HAM bands. And a house running high speed power > line networking can turn into an interesting emitter of noise in the > various radio bands. > > So we used four modulation frequencies and a modified Controller Area > Network (CAN) protocol to allow CSMA/CR (Carrier Sense, Multiple > Access with Collision Recovery). Now a null point right at an outlet > socket at one frequency would not be a null at a different frequency. > > Alas, the IP disappeared into a large Chinese corporation and that's > the end of it at the moment. > > John Dammeyer
Interesting bit of history, thanks John. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
