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Message-ID: <002501c6cb51$0e692880$0300a8c0@lark>
From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <584.3adc3c8.3224be5f@aol.com> <001c01c6cb25$9d825270$0100a8c0@W1KW>
Date: Tue, 29 Aug 2006 10:30:56 +0100
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Subject: Re: LF: DCF39
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Hi Geri, mmmm I hope not, because random changes in level will kill it as a
useful beacon source, and relagate it to the category of QRM.

Cheers de Alan G3NYK

----- Original Message -----
From: Holger 'Geri', DK8KW <geri@dk8kw.de>
To: <rsgb_lf_group@blacksheep.org>
Sent: 29 August 2006 05:43
Subject: Re: LF: DCF39


Hello Markus,

very interesting graph.

I guess at the currently high energy costs someone at the Europ�ischen
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 -----
  From: MarkusVester@aol.com
  To: rsgb_lf_group@blacksheep.org
  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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