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Dear LF,
At 15:04, I had deactivated the noise blanker,
which is normally used to cut out most of the DCF39 modulation clicks.
Thereafter, you can see the true spectral content of the FSK sidebands. The
strong purple (ie. northerly) vertical
lines intruding from the top are from DCF39 Magdeburg, and the
red (ie. easterly) ones near the bottom are from HGA22 Budapest.
Between 15:05 and 15:12, there is a dense block of
telegrams, which is transmitted from all "EFR" stations in near
synchronism. The newer DCF39
transmitter (which was put to service in 2007) obviously has virtually
unfiltered modulation, with keyclicks going down all the way to
about 136.5 kHz. Below that, HGA22 takes over, with a somewhat
narrower modulation but of course closer to the carrier. The two of
them combined are covering up all of the LF band here.
The gaps in the red HGA spectrum are clearly
visible, at all multiples of approx. 200 Hz from the active space frequency
135.77 kHz. There are blue dashes from "Z" (SM6BHZ?), fitting in nicely at
137.176 kHz. The different effect on proposed Eu slot frequencies can be
seen on http://df6nm.bplaced.net/LF/testEu1012121515.jpg .
Interestingly, DCF39 is different in that there are
actually two sets of gaps, spaced at 200 Hz intervals around both the mark
and space frequency. This is probably due to a subtle difference in the
serial stop-bit timing between the transmitters. In effect, nulls are at at
137.765, 137.565, etc. kHz, and also at 137.83, 137.63, ...
kHz. In the capture there are faint yellow dashes from OE5ODL at
137774.5, indicating that our TA slot allocation is actually just
a tad too high to fit into a gap.
Best 73,
Markus (DF6NM)
Sent: Sunday, December 12, 2010 3:13 PM
Subject: LF: New Eu slot 136.177 kHz?
...
Here in Europe and Russia, a possible
disadvantage of going down is that we would also come closer to HGA22. This is
the 100 kW telecontrol transmitter in Budapest, an idle carrier sitting at
135.43 kHz, and excursions to 135.77 during FSK bursts. Normally these
bursts appear every 11 seconds, but at times there are annoying blocks of
consecutive telegrams several minutes long. Here in Bavaria, the FSK
modulation sidebands are visibe up to about 136.5 kHz, but there are
pronounced spectral gaps due to the 200 bd modulation. These clear gaps
are near 135.97, 136.17 and 136.37 kHz.
...
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