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Author Topic: Additional Thoughts  (Read 11709 times)

N0PQK

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Additional Thoughts
« on: May 01, 2017, 01:14:13 PM »

That is refreshing. I wonder how much of the older PLC system has been replaced by modern techniques and UHF / Microwave frequencies.

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ยง 15.113 Power Line Carrier Systems.
* * * * *
(g) Special provisions. An electric power utility entity shall not operate a new or modified power line
carrier (PLC) system in the 135.7-137.8 kHz and/or 472-479 kHz bands if a previously coordinated
amateur station pursuant to Section 97.301(g)(2) of this Chapter is located within one kilometer of the
transmission lines conducting the PLC signal.
* * * * *


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N3QE

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RE: Additional Thoughts
« Reply #2 on: May 17, 2017, 07:19:54 AM »

That is refreshing. I wonder how much of the older PLC system has been replaced by modern techniques and UHF / Microwave frequencies.

100kc-200kc carrier line transmission by the utilities was state of the art in the 1940's.

Back in the 1970's I had an Elmer who was benefiting from the decommissioning of Westinhouse 136kc line carrier units - each 136kc "transmitter" had one 807 tube for the oscillator and six 807's for the amplifier in it. There were also these big-ass ginormous coupling capacitors for injecting and extracting the 136kc, as well as ginormous chokes for segmenting the system.

In the 1970's this stuff was being replaced by low-band VHF telemetry with whips antennas as strategic locations.

The most recent trend is fiber optics for SCADA. This goes back at least 20 years. They call it "Optical Ground Wire": https://en.wikipedia.org/wiki/Optical_ground_wire
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KM1H

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RE: Additional Thoughts
« Reply #3 on: June 22, 2017, 10:47:00 AM »

During WW2 carrier line AM and CW was used by hams that had enough smarts to be able to build them from QST or other articles; there were no commercial products.

Carl
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