[Lowfer] Last Chance on 136 kHz Rulemaking

[JD]

>>> 3. They mention the worry about interference to hams - has anyone ever 
>>> seen a PLC signal?  With our narrowband techniques interference should 
>>> not be a problem.

This is a point especially worth addressing in replies to the FCC, IMO.

Yes, actually, we've all seen PLC signals.  They're all over the entire LF 
spectrum, though less so in the NDB bands and above.

For the most part, however, they are not a problem, precisely for the reason 
you mention, Craig.  The ARRL alluded to this in their original comments, 
and it's probably worth more of us responding to.  The utilities clearly 
have huge misimpressions about the kind of amateur operations that are 
possible in the band, and they're trying to sway the FCC's opinion based on 
this unrealistic notion.

While it's true that a strict interpretation of Part 15 would require them 
to protect our licensed operation, it's also true that a strict 
interpretation of Part 15 (and the Communication Act of 1934 as Amended, for 
that matter) does not permit them to prevent other users from sharing the 
spectrum in the first place!  None the less, the Commission has accorded 
them these special privileges for so long that their delicate condition has 
become a matter of public necessity (for now).  But the bottom line is, that 
untenable dichotomy, historical absurdity though it is, need not change in 
order for us to share the spectrum.

In my view, it's all a question of sound engineering.  From prior studies, 
we now know with good certainty how much interfering signal it takes to 
prevent PLC systems from functioning reliably, and so having a specific 
radiated power limit enables one to determine how far one must be from any 
such transmission line to ensure safety.

It's just that simple.  At LF, you're not going to have hard-to-predict 
reflections off of nearby objects adding to field strength, as happens at 
VHF for instance (just the opposite--it's unexpected absorptions we have to 
worry about in our antenna installations).  At LF, over distances as short 
as we're talking about, propagation is very stable.  Thus, the planning 
factors established for maintaining specified separation between hams and 
PLC users can be taken as extremely reliable, and it works out to be 0.95 km 
at one watt EIRP.

If they're worried about mobile operation near a power line being risky, 
fine--the FCC prohibits mobile operation so long as we have to share the 
band; problem solved.  (Who's going to operate mobile, anyway?  It's 
challenging enough to try to hear anything at LF in a vehicle, but it's 
ludicrous to think of trying to transmit mobile.  As I hinted in an earlier 
post, you'd be generating huge corona discharges if you tried to achieve 1 W 
EIRP with a 102" whip.  You'd have the EPA citing you for ozone pollution 
long before you became a risk to power lines!)

I think we need to emphasize that we understand the utilities' unique needs 
as they now, while simultaneously making it clear to the Commission that the 
power companies are utterly wrong about sharing being impossible, and we 
understand how it can be done.

John