Monday, November 17, 2008

Alleged HomePlug Document Suggests Awareness of Interference Issue

Publically, the two standardizing industry associations for the HomePlug and DS2 powerline communication standards act as if there's no problem with RF emissions from devices which are basically wideband transmitters putting appreciable HF energy into AC power lines, which unintentionally serve as very efficient transmitting antennas.

A document alleged to be an internal "executive seminar" at the HomePlug Alliance has been posted to the files section of UKQRM. If this is real, it strongly suggests that someone working for the HomePlug Alliance is completely aware that a problem exists. Members of UKQRM can go to that group's files section and download this document.

What we have here is something at least resembling an internal presentation of PowerPoint-like slides stored as a .PDF file. Its heading on each slide is "Homeplug Executive Seminar." It shows measurements proving that their devices do not meet European electromagnetic compatibility standards, and had to gain the CE mark by exploiting loopholes. Subsequent slides claim that it's all just a problem with the standard test setup, which is simply unfair to powerline devices, that's all.

If this means that the whole idea of sending data through active power lines is so stupid that excessive RF power must be used to make it work even a little, I agree.

From page 4:

Safety, immunity and harmonics are correct but almost all PLC devices pass over the CISPR 22 class A, B limits so failed the test and we could not generate (directly) the DoC (Declaration of Conformity) needed for Europe

This is accompanied by a chart which looks like a dBuV over frequency run. Indeed, it shows 85 dBuV all the way across HF under their test parameters, except for sharp notches in some (NOT ALL) ham radio bands. This is indeed well in violation of EMC standards.

What do you do if you fail the test? Why claim that the standard is too old fashioned, of course, and rig up your own test so your product passes, despite a known EMC problem. Continuing, on page 5:

Several studies have been done on this current issue
• Some experts have demonstrated that the current interface used for the test was not accurate for the powerline and have proposed their own schematics (gaining up to 10 dB so passing class A and B)

Few competent bodies have proposed their own method
• They created their own measurement method and built for the manufacturer, the TCF (Technical Construction File: this is the second official way to gain the CE mark, specially when a unit do not follow at 100 % the harmonized standards)
• So they demonstrated with their method that the unit will not harm the “network”
• With this TCF, the CE mark could be affixed to the product so the PLC device could be sold in Europe

The "Final Solution?" Why, pressure international bodies to change the law, of course. Page 6:

A sub group of the CISPR was created to work on this issue
• The interface used to test the CISPR 22 test was developped a long time ago and is not fair for a measurement on the power line
• CISPR SC I PLT TG is working to find a test method that will properly test power line communications ports.

And, if that doesn't work, of course maybe if you lobby hard enough, the ITU will simply clear out a huge swath of HF for you. Page 8:

As of today the best case for this new CISPR I 89
standard is 2009
ITU-R: We have also investigated the possibility to
obtain a dedicated band for the PLC, it will take if
accepted around 10 to 15 years…
During this interim period the TCF will be always
the best compromise but could be subject to

In other news, BPL is not dead. IBM announced that it seeks to build an extensive system to bring broadband to rural areas. In other words, if you try to escape the cities, you will find that HF has been jammed in the country too.

I'm glad I'm not a conspiratologist. The idea of a worldwide total blockage of HF would have me going on Art Bell (or his replacement) by now.