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Posted by Glenn on August 09, 2026 at 22:38:35.
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PLC is a name that I am very familiar with. In my world it is a complex and useful device. A programmable logic controller has been a very contributing device. Early on they were very simple and much like boat anchors. Now they control large industrial processes/facilities and are a vital part of our world. We could not manage the intricacy of this day and age without them. But there is another PLC. The power line communications system. They are about as archaic as the old boat anchor PLC's that I mentioned above. I have been monitoring the power line communications system in my area for about the last three years. Before that I believed them to be a broadband low frequency system because of the observations that I had made. I believe that I was wrong. The power line communications systems that I monitor in this area are usually 8 channels of digital or analog data. I believe I have two systems in my area that I can receive. One close up and one more distant but on the same power line. The close up system does not have stable frequency control. The second more distant seems to have better. Their frequencies are (I am approximating) 130 kHz to 400 kHz. Do they interfere with my reception? Not much but when they shut the closer system down it gives me a blast of frequencies right smack in the range of 160 to 190 kHz for a few minutes to sometimes a few hours. Their "channels" have simple status as well as a simple tone and carrier analog. I usually see them for a short while in the evening and sometimes in the morning. These power line PLC's are likely inside their substations. What is ironic is that each of these substations have microwave systems available to do the same job. I suppose they may consider the the power line PLC as a backup. But the microwave is not being used as a primary. In fact I don't think the microwave is tied into these status points. Why would an operator start the power line PLC up and let it stabilize and then retrieve his information when he would instantly have it available through the microwave system? I don't know but I would like to know their thinking. The industry I worked for had two or three methods of redundancy based on what was available. Broadband ether net from the company system, cellular modems or in some case telco broadband. One other division used satellite as a backup. There were security layers to keep knot heads out. I am not inferring that they should not have the power line PLC but I seriously question whether they are needed or not and if something more secure or more useful could be put to use. Do any of you detect such systems in your area?
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