From: "Dave Sergeant" <dsergeant@btinternet.com>
To: rsgb_lf_group@blacksheep.org
Date: Thu, 15 May 2003 14:34:26 +0100
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Subject: Re: LF: No US Ham Band
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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

dsergeant@btinternet.com
http://www.dsergeant.btinternet.co.uk