Hello Markus, LF,
At 23.00z I want to move an Eu-window of my grabber on "new"
frequencies, with the center 136.172 khz.
If someone is interested in control of the transmitting on "old"
frequencies
at this night, please inform. I will make display of concrete necessary
frequency in a small window.
73
Andrey
Dear LF,
after some detailed investigation of the interference situation at
W1VD and
VE7TIL, we propose to move down the recommended Eu TX slot by 5 Hz,
from the
current center frequency 136177 to 136172 Hz. The latter seems to be
clear
for Jay within about +-4 Hz (ie 136168 to 136176 Hz). HGA sidebands in
Europe are no worse as we are still within their spectral gap.
I would ask all interested receive stations to include this range in
their
observations, and look for possible interference at this QRG. If no
serious
problem pops up, we could all shift our grabber slots.
Best 73,
MArkus (DF6NM)
-----Ursprüngliche Mitteilung----- Von: Markus Vester
<[email protected]>
An: [email protected]
Verschickt: So., 13. Feb. 2011, 21:53
Thema: Re: New Eu slot 136.177 kHz?
Dear LF group,
the considerations which led to the choice of a new Eu waterhole have
been
explained in a posting from Dec 12th, attached beneath. Here's a brief
summary of the current situation:
- We clearly need separate E-W and W-E slots, due to side effects of
noise
blanking, and imperfections of transmitters and receivers.
- The Canadian West coast (Scott, Steve) experiences wide-area
interference
(presumably PLC), centered on 135700 and 136320. This is what
triggered the
search for an alternative Eu slot.
- Central and Eastern Europe suffers from HGA22 sidebands, except for
a few
narrow slots (135.975, 136.177, 136.38) . The density of FSK telegrams on
DCF39 and HGA22 has been increasing.
- We want to stay far enough from 137.0 in case CFH would be fired up
more
regularly.
- But we now have the problem that Jay is affected by local QRM around
136.177. It consists.predominantly of a group of unstable lines,
spaced by
about 1 Hz.
I had secretly hoped that Jay might ultimately find a way to identify and
fix the problem locally, but this may simply not be feasible. How far
up and
down does this interference extend in frequency? I'm also not sure
whether
Warren is actually having the same difficulty or not.
Now we have the dilemma that if we stay on the new slot, we may loose
many
excellent high-quality observations from Jay. If we move back to the old
one, we give away the slim chance of being picked up by Scott or his
friends
during that special Transpolar night.
The best choice may be to move on again. If we decide so, we will then
need
to collect information regarding bad and good channels from all key
players,
perhaps by detailed analysis of wav recordings of the whole lower part of
the band.
Best regards,
Markus (DF6NM)
From: Markus Vester
Sent: Sunday, December 12, 2010 3:13 PM
To: [email protected]
Subject: New Eu slot 136.177 kHz?
Dear LF,
after considerations with Scott VE7TIL, Mike G3XDV, and Laurence KL7UK, I
would like to discuss moving the European intercontinental transmit
slot. It
is currently centered on 136.320 kHz, and I propose a new center
frequency
of 136.177 kHz.
This discussion was initiated by VE7TIL, who is plagued by severe QRM
lines,
to an amount that he considers the vicinity of 136.32 kHz as being
unusable
for him. Scott believes that the interference is caused by a PLC system
leaking from a nearby powerline, and that it will probably not be
possible
to fix it locally. Of course it can be disputed whether QRM at one
receive
site would be reason enough to change a band plan, which has been
useful for
a number of years. On the other hand, there is only a limited number of
receivers around the world. And we would certainly like to have Scott
onboard, as the path from Eu to the American West coast is certainly
one of
the most challenging ones.
A few years ago, we decided to move Eu transmissions from the original
135922 Hz to 136320 Hz, driven by a wider gap in the American Loran-C
line
spectrum. Since the shutdown of US and Canadian Loran chains, this is no
longer an issue.
One benefit of going back to a lower frequency would be moving further
away
from the Canadian military transmitter CFH, which occasionally sends
out a
strong FSK (or MSK) signal centered on 137.0 kHz. It would be
interesting to
get some information how much this one actually affects the American LF
background at different frequency offsets.
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.
We looked at 136.37 first, but this would not fix the problem for Scott.
135.97 seems worse in Europe due to Luxembourg effect impressed on
HGA, and
is also getting close to the Greek military SXV. So we decided to
focus on
136.17 kHz. A closer look revealed that this very useful FSK minimum is
actually centered on 136177 Hz, and about 8 Hz wide.
For the last few days, I have been running my grabber
http://www.alice-dsl.net/df6nm/grabber/Grabber.htm with a split window,
showing both the present and the proposed new slot side by side. The
direct
modulation sidebands (showing as red bands) are much better on the new
frequency. Nighttime Luxembourg QRM generally does not appear to be
worse,
despite being closer to the HGA carrier. We also expect the latter to
be a
more regionally confined effect, which will not be present in remote
areas
of the world. After all, the main purpose of Eu-slot grabbers within
Euroupe
would not so much be ultimate sensitivity, but rather to provide a
monitor
for intra-Eu transmit frequency coordination, and a comparison log for
verification of DX receptions.
Before coming to a possible decision to move the Eu frequency band, we
would
like to collect some feedback on the receive situation in different
parts of
the world. Traditionally, Eu slot transmissions were primarily targeted
towards the American east coast. But of course we would like to include
other areas of the world. How useful would the proposed slot be for
example
in Russia or Japan?
Active Loran-C rates in Japan are GRI 8930 (lines at 136175.812 and
1368181.411 Hz) and GRI 9930 (lines at 136173.212 and 136178.248 Hz).
Russia uses GRI 8000 with lines at 6.25 Hz multiples, and perhaps GRI
7950
(136178.157 Hz). As the frequencies are very accurate, these lines are
very
useful calibration markers.
Now, your opinions please!
Best regards,
Markus (DF6NM)
