[Lowfer] New MW Allocation in the U.S. & Questions about LF

Wed Feb 15 23:22:34 EST 2012

Hello Perry / group

Thanks for your very thoughtful explanation.  A very similar one was 
presented by VY1JA as part of the of his Canadian experiment on the 
137KHz band.  He even tested his theory with the cooperation of Yukon 
Hydro as he has transmission lines passing over his property and was a 
protection and control expert for them for many years and borrowed a few 
pieces of test gear as well...  No issues where noted during his QRO tests.

I agree politics and turf wars, certainly not common sense.

Here in BC, there appears to be an ever increasing complexity to PLC 
signals as I'm fairly close to transmission lines I have noted a 
distinct change in their characteristics.  They have gone from using 
primarily FSK type data with a carrier to something that appears to be a 
BPSK signal with harmonics all up the band...  About 4 years ago a 
wideband data stream started too that is heard anywhere near BC Hydro 
transmission lines.  Considering the Canadian Navy uses this spectrum 
with considerable power in close proximity to the densest population 
area in BC and there has never been an issue here or in WA state I 
suspect the PLC bug bear is a non-issue and a convenient way to avoid 
the issue by the FCC.

You can monitor the goings of BC Hydro and all the other LF 
noise/signals on my Grabber 2 page.

I really wish the US would authorize the LF band as it would certainly 
spur some new and interesting activity.  Most importantly the LF and new 
MF bands will be places where interesting NEW stuff happens and may 
attract NEW young hams with technical skills to enjoy the challenge.

If there was ever a time for the bureaucrats to get their heads out of 
their butts and allow true amateur experimentation it is NOW.

73 Scott
VE7TIL
http://www3.telus.net/sthed/argo/

On 2/15/2012 7:58 PM, w8au at sssnet.com wrote:
> At 05:40 PM 2/15/2012, craig wasson wrote:
>> More likely the power companies' opposition to the LW allocation was
>> the power companies control generation and switching
>> using carriers in the 135khz range.  Simple on/off keying with no
>> security of any kind.  So a random signal in that range might shut
>> down a power plant or feeder.
>>
>> You would think that in this day and age they would want the power
>> grid to be more secure.
> Actually "security" was/is not a problem.
>
> A similar discussion on this topic occurred over 5 years ago with a debunking
> of Power Industry claims.   But it's hard for government to ignore the UTC
> (Utilities Telecommunications Council) speaking as if their arguments
> were true.
>
> The Utility use of LF is nowhere as extensive as it was years ago
> before Microwave
> and then Fiber Optics mediums were used.  All voice comms, generation control
> (of power plants), telemetering and data are gone. The migration from
> LF to Microwave
> and Fiberoptics was due to the much greater bandwidth available.
> Power company use
> of the LF spetrum is from 50 - 300 khz at most, and only provides 250
> kHz bandwidth.
> What basically is left on PLC is called Protective Relaying and
> Transfer Trip.
> These are non-intelligent single or dual carrier transmissions.
>
> Protective Relaying is used all along a string of connected
> substations to eliminate the
> tripping of every breaker along the path when an overcurrent fault
> occurs.  When a fault
> does occur, all substations (and generator plants) send a single
> carrier to each station
> to which they are connected.  The lines that are not at fault will
> convey the RF between
> stations and tripping will be blocked.  The only line that will not
> be blocked is the
> section that has the fault and it's RF signal will be lost because of
> the fault and will allow
> the associated breakers to trip, thereby keeping consumer power
> outages contained
> within a small area instead of the whole region.
>
> Let me add here that PLC (power line carrier) receivers are not
> sensitive!  They are
> designed to take volts, not microvolts, to activate them.  This is
> because sensitive
> receivers would overload on the noise levels usually found on HV
> transmission lines.
> The typical low loss of 1 dB per mile on HV transmission lines then
> allows PLC transmitters
> to run anywhere from 1 to 10 watts with volts to spare at the
> receiving end. .
>
> The general rule is that one should not hear a PLC signal beyond 1/4
> mile because
> the 3 phase parallel lines that are used to conduct these signals
> effectively suppress
> radiation, very similar to our open wire feedlines.   So, conversely,
> incoming signals
> from radiated sources will not normally be picked up by these lines.
>
> AND, even if they were, and the PLC receivers were activated, nothing
> would happen.
> As stated above, this would act to prevent any tripping of breakers,
> not cause it.
>
> Transfer Trip is a dual signal that runs continuously between major
> power plants and
> major substations.  (345kV - 750kV lines)   These signals are spaced
> a number of kHz
> apart and are used to actually trip breakers, not prevent it.  When
> one area has a fault
> the two signals are shifted 1 kHz in opposite directions.  For
> instance the lower of the
> two signals will shift 1 kHz low and the higher signal will shift
> 1kHz high.  This provides
> the security.  An interfering signal will never duplicate this.  AND
> the transmitters doing
> the freq shifting will elevate their power levels by as much as 10dB
> just to make sure they
> are received at the other end.
>
> Again, coupled with PLC rcvr insensitivity and higher Transfer Trip
> xmtr power, the security
> is maintained.
>
> So, call it Turf Wars, or Politics.... it definitely isn't common sense.
>
> Perry  w8au   (First Energy Corp, ret)
>
>
>> On 2/15/12, KD7JYK DM09<kd7jyk at earthlink.net>  wrote:
>>> : Can someone refresh my memory on what the objection within the US is to
>>> : the WARC 07 allocation at 135.7-135.8?
>>>
>>> Wasn't it due to a lack of  kickbacks to shut up the power companies and
>>> their lobbyists that know nothing about radio?
>>>
>>> Kurt
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