Date: Thu, 30 Dec 2004 09:33:27 +0000
From: "J. Allen" <vy1ja@northwestel.net>
To: rsgb_lf_group@blacksheep.org
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Subject: LF: Power Line Carrier gear   de VY1JA
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John,

I would be quite surprised if Power Line Carrier equipment were disrupted by 
amateur equipment.  The power lines are rotated physically to balance fields 
for a number of reasons.  It just happens to help prevent line transmission 
of PLC signals and pickup of our LF signals.

Installation, and maintenance of PLCs  came under my supervision until I 
retired from Yukon Energy Corp three years ago.  If a small utility like YEC 
installs and maintains things with this care, I suspect that the fears of 
power company problems in the populated world south of us are totally 
unfounded....

I will find out some of this, because several of the men in my previous crew 
are still with the power company and are all licensed amateurs.  My 
experiments will be done in such a way that they can monitor my early 
transmissions and signal levels (or as I suspect, absence of them) on the 
PLC subsystem.

It is my belief and expectation that this kind of monitoring and testing can 
demonstrate that amateur LF work can cohabit the same neighborhoods as PLC 
SCADA control systems.  The 138,000 Volt line which carries the PLC signals 
is approximately 100 meters from the tower which will be the 137 kHz 
antenna.

The way the PLC works is that the power transmission line also is used as an 
RF transmission line.  The PLC transmitter runs approximately 75 -150 Watts 
directly into the line and the line carries that to a matched load of a 
transmitter/receiver pair on the opposite end of the line.  With the high 
signal levels that are forced into the line and received on the opposite 
end, I cannot see how the small amount of signal that is picked up by the 
antenna effects of the power line can compare or how it can cause any 
trouble.

Has anyone in the UK heard of any LF transmitter causing problems with 
PLCs?.  If so, I would appreciate knowing the details.

J.

VY1JA
CP20kw