2021-05-10 Power Lines For Data Communication

In the late ’60s a high school friend and I worked part-time with a guy who did FCC type acceptance and other radio engineering. He bought used Hewlett-Packard, Tektronix and other high quality test equipment. One was a frequency standard which was directly traceable to the National Bureau Of Standards, now known as NIST. He checked frequency counters using the 10 MHz WWV stations. He also checked frequency counters against some AM broadcasting stations. One was an AM station in San Francisco, which can be heard in LA at night. He noticed that the frequency, which is supposed to be kept within a close tolerance, was changing periodically but still within tolerance. It seemed to be transmitting frequency shift keyed code. He asked the station engineer but was given no information other than it was secret. He came to the conclusion that the military was probably using it to send encrypted messages to submarines at sea.

The point is that it’s possible to use radio transmitter for something other than its intended purpose. So I thought about this idea.

The electric companies have some frequencies (VHF or ??) assigned to them for sending control signals between stations and equipment in the field. The big trend now is the IoT – internet of things. Residences are becoming more automated. If the electric companies have a need to control loads or generation sources on the grid, it would be very helpful if the slaves could be controlled remotely over the power lines.

The smart gas and electric meters are controlled over a Zigbee mesh network. The messages are stored and forwarded by a peer-to-peer network. I assume that this means there is no ability to control the amount of delay between the sender node and the receiver node since the number of hops and delays between hops is not known. This wouldn’t be a problem if the messages were sent directly over the power lines.

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