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Hello Markus,
very interesting graph.
I guess at the currently high energy costs someone
at the Europäischen Funkrundsteuerung GmbH
(EFR) must have started to think if it is really necessary to put a 40 to 50 kW
permanent carrier on the air to remotely switch on and off street lamp.
These 3 dB steps might be tests for a system to reduce the carrier level at
least between the telegrams to save costs.
Best
73
Geri, DK8KW / W1KW / DI2BO
----- Original Message -----
Sent: Monday, August 28, 2006 11:47
PM
Subject: Re: LF: DCF39
Dear LF group,
stimulated by Jim's
observation of DCF-39 outages, I set up SpecLab's plotter to monitor the
138.83 kHz carrier from Sunday afternoon till tonight.
The two dark
blue traces show the maximum and mininimum amplitudes within each two minute
measurement interval. The usual 3 mV/m carrier, attenuated at the passband
edge, places the upper trace at about 40% relative magnitude. The minimum
trace reflects the energy spread during the short telegrams, about -8dBc when
smeared by 0.34 Hz resolution bandwidth.
On Sunday afternoon, I aurally
observed many short interruptions, where the carrier went off completely after
a telegram, and ramped back up after a couple of seconds. These appear as dips
to zero in the minimum trace. There was also a long outage between 12:00 and
14:15.
Another interesting feature is the apparent power switching.
These 3 dB steps were again accompanied by short breaks, and occured at 20:40
(up), Monday 5:40 (down), 7:40 (up), 8:50 (down), 9:10 (up), 9:35
(down).
The light blue trace shows the recorded azimut, which should of
course be constant and due north. The irregular nighttime variations are
usually introduced by ionospheric multipath.
However the slower daytime
deviations (300 to 350 degrees) are an artifact due to E-field antenna
detuning by moisture. This "summer antenna" is a just piece of wire strung
among the branches of a fir tree, and series resonated with about 10 mH.
Whenever it starts to rain (which was often, e.g. at 16:05), its phase is
retarded and the apparent azimuth deviates clockwise, letting the SXV trace on
my grabber display turn from orange to greenish (makes sense doesn't it ;-) I
have tried to minimize this by loading the antenna with a high receiver input
impedance, but there is probably also a direct dielectric effect disturbing
the local electric field.
The red traces and dots are for SXV around
135.75 kHz. They show the usual morning and afternoon fieldstrength minima, as
well as the same weather artifacts in azimuth.
73 and best
wishes
Markus, DF6NM
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