Poul-Henning Kamp kirjoitti:
I spent some time capturing some data today.
The measurements is from my $20 loop-antenna in the attic, which is
something like 8 meters up and 10 meters besides the lawn-mower loop:
http://phk.freebsd.dk/time/20150509.html
In the Finland that problem is even worse! For me it's called Savon
Voima, our local power company (but also many other power companies
around the Finland). They are using PLC based remote readable utility
meters. These meters communicate with power lines, using ancient 1200
bps. FSK using 83.2/93.6 kHz frequencies. Because the power grid is not
designed for this kind of communication, those frequencies will of
course leak all over the places.
Because the metering hardware is cheap crap made by Slovenian company,
those frequencies are not very accurate/narrow and so they block the
DCF77 77,5 kHz band totally! Because all in-house wiring act as an
transmitter antennas, the field strenghts inside the houses can be as
high as 120 dBuV/m.
The system is so stupid that it need to communicate 24h to transfer less
than six digits (the reading of the utility meter), which is basicly
needed once per month for elecricity billing. Every meter can act as
repeater to other meters.
The DCF77 problem was verified when there was large blackout. During
this blackout the DCF77 clocks was syncronized at moments, when they
never synchronize normally.
When this was reported to Finnish authority called Viestintävirasto
(it's Finnish version of FCC), they say that this doesn't matter - the
DCF77 is not "protected" in Finland (even when you can buy radio
controlled clocks from the shop).
The whole idea about PLC is so stupid and the universal stupidity factor
of the people designing these is so high that there's nothing to do
anymore. Even the power company said that this is not reliable system,
having much of interferences, the readings are not transferred
succesfully all the times. But still they buy this kind of crap, even
when knowing it weaknesses. Clearly the marketing guys of PLC systems
knows their business and they can even cope with local auhorities so
that there's no problems to install these everywhere.
I think that we have lost the game! Only way to set the clock is to
build your own DCF77 transmitter - like the local authority said: the
DCF77 band is not "protected" - at least here in Finland...
--
73s!
Esa
OH4KJU
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