On 15 May 2003 at 12:27, James Moritz wrote:
>The FCC said a new amateur LF allocation is not justified "when
>balanced
against the greater public interest of an interference-free power
grid."
Have they got this the right way round? Virtually all radio services
on LF suffer a continual and steadily increasing amount of
interference from the power grid, but I have yet to hear of an
instance where radio signals cause interference problems to the power
grid. All seems a bit "Alice in Wonderland"...as if a secretary
somewhere had made a typo, and no-one who knew anything about the
subject had ever checked it.
I downloaded and read the full FCC report (linked from the ARRL site)
which explains their decisions in more detail. The problem is
possible interference by amateur signals to the PLC system used by
the power line companies to control power line switching - note that
this is nothing to do with PLT, or broadband, but a FSK system they
use.
Despite assurance from ARRL that an amateur would have to be within a
few 100 yards of the line for there to be any problem, at which
distance the power line QRM would be horrendous, FCC have gone along
with the power companies in rejecting the proposals. The fear is of
switching relays being incorrectly turned off by amateur interference
and causing power blackouts. Of course a system (in itself an
unlicenced user of the band) which does not fail safe in these
situations is badly designed anyway.
The document is worth reading, but somewhat depressing. Both in the
136 case and in the 5MHz one they have gone 100% with the objectors
and the amateur case has been totally ignored. If you download it
note that it is a very bloated Word document at 1.3Mb. In pdf it
comes down to 275k, and saved in Open Office format (zipped XML) it
is a mere 49k!!
73 Dave G3YMC
[email protected]
http://www.dsergeant.btinternet.co.uk
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