This message is from the Technical Coordinator (TC) for the Michigan Section and is a perfect example of why power companies should not get involved in sending RF over power lines. It also seems to be an excellent recommendation for our ARRL Publication that was used by a telephone industry professional. Wallace is KE8HR, and manager of network engineering for SBC in Detroit. Dick Mondro, W8FQT ----- Original Message ----- From: "MURRAY, WALLACE W (AIT)" <wm3912@sbc.com> To: <dalew@dundee.net>; <w8fqt@arrl.org>; <JBRIDGEW@fcc.gov> Cc: <ke8hr@comcast.net> Sent: Wednesday, October 29, 2003 4:52 PM Subject: AC Power Interference
Two weeks ago, I had an opportunity to determine why all the DSL customers in a two block area in Mentor Ohio were out of service. The POTS telephone service was not effected. Cordless phones in the area were not working. As you can imagine, this was a problem that had existed for over a week and many hours of overtime had been expended by local telco craft. Our inductive coordination and electrical protection people had been involved but decided that this was a RF interference problem and called for help.
The symptoms were as follows, broadband noise from below the broadcast band up to about 6 MHz, and physically centered around a street which served the effected customers. The characteristic signature as viewed on the spectrum analyzer was spark interference from a single source. This spark interference signature could be seen on a loop antenna tuned to 6 MHz, or connected directly to the customer's cable pair.
Early on the power company, The Illuminating Company, that serves metro Cleveland had been called, but dismissed the noise to the telephone cable as being poor bonding and grounding. They reluctantly worked with SBC to add additional grounds. None of this did any good. The power company now took the position that it must be the telephone company.
This is when I was called and traveled to Cleveland and found the above spark interference. Upon being told that the "experts" were here from Detroit, the power company commented, "if they know so much, why don't they tell us where the problem is".
I knew that there was a new AC power interference Handbook from the ARRL and a visit to AES resulted in a copy. I now had pictures that I could share with Power Quality person from the power company. Further analysis resulted in determining that we were suffering from spark noise being generated in the URD or underground residential distribution. The telephone cable was buried in the same trench as the power cable about one foot above. The power quality person stated that he had never seen spark interference in the underground cause this kind of interference. It should be noted that the interference we were experiencing was perfectly described in Chapter 3 of the AC power interference handbook. HF noise on the "dip" pole, where the URD goes underground was strong.
Spark interference causes a broad spectrum of noise up to 1000 MHz. Further, the closer to the problem you get, the higher the frequency of interference should be observed. Based on this we opened up the squelch on the company 450 MHz radio and drove up and down the street looking for hot spots of noise. We found several, with the strongest being near a pad mounted transformer. The power company finally arrived with tools and equipment to open up the 13.2 kV pad transformer or area where the UHF interference was the greatest. When the case on the transformer was opened, and the power connectors removed and re connected the noise quit. Pictures in Chapter 3 of the book show all the pieces. Needless to say, the DSL circuits came up and worked better than ever.
Several observations. The power company was fully equipped with specialized equipment for quickly isolating the interference, but I never saw them use it. The power company assumed that because basis telephone service was not effected, the DSL data service was of no concern, to say nothing of the broadcast interference taking out a local 50 kW clear channel AM station and HF radio interference. Spark interference does not generate heat or waste power. Again, power company has little incentive to act. In looking at the ARRL web site for most recent FCC violation notices, two were sent by Riley Hollingsworth to the Counsel at the Ohio power company. This same power company is highly suspect for contributing to the recent power outage. Do we see a pattern here.
Final observations. Is BPL something that the power companies really want to do? My experience demonstrates that they have neither the desire nor the corporate focus to use the radio spectrum in a responsible manner. The power companies are not equipped to find and solve RF interference problems. Job skills are different between a power company lineman and a radio technician. My experience with this noise and others is that the power companies will not invest in the training or if they do, will not support the findings of the power quality people. There will be a significant number of people needed to chase interference if BPL is permitted.
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