[ARC5] LF NDB's

[Mike Morrow]

> ...unfortunately, the 137.5 KHZ ham band is not available to us 
> in the USA. What I had heard was that the power company's successful 
> lobbying kept us from getting us that band.

Lobbying is an inappropriate term.  Rulings on issues such as this were
not decided in congress, but by the FCC.

The concern is associated with large power line transmission networks.
Transmission line protection systems (phase-to-phase fault zone 1/2/3
relays and phase-to-ground fault relays) require the relay systems at
each end of the transmission line to "talk" to each other and to nearby
breaker trip relays, sending breaker trip-blocking or trip-permissive signals
designed to ensure that only a minimum number of breakers trip to isolate
a fault that may actually be sensed by several protective relay systems
at multiple substations or switch yards.  Traditionally, these signals have
been sent on VLF, LF, and low MF frequencies on the transmission lines
between substations.  There are also other signals continuously being
sent on similar frequencies between substations and switch yards to allow
conditions at one substation to trip the breaker at the far end of a line.
(If you're ever near a large substation and see large barrel-shaped and -sized
structures on some of the power lines at the station, you're looking at a
large wave trap or RF choke that indicates that such signals are conveyed
on that line.)  Some power engineering organizations are afraid that these
"carrier" relaying and remote tripping signals could receive interference
from local ham operation near a transmission line.  It's not really all
that likely, and the industry is slowly converting most of these signal
systems to a microwave or fiber optic medium.  So...maybe someday!

I think the U.S. 600-meter band experimental station license program would
be more interesting anyway ( http://www.500kc.com/ ).

Mike / KK5F