Message-ID: <4D04F7A2.9050303@online.fr>
Date: Sun, 12 Dec 2010 17:26:10 +0100
From: =?ISO-8859-1?Q?=22Jean-Pierre_M=E9r=E9_=28F1AFJ=29=22?=
 <jpm.f1afj@online.fr>
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; fr; rv:1.9.2.13) Gecko/20101207 Thunderbird/3.1.7
MIME-Version: 1.0
To: rsgb_lf_group@blacksheep.org
References: <FE0D24C032AE4336BA9047835511B3E3@White>
In-Reply-To: <FE0D24C032AE4336BA9047835511B3E3@White>
Subject: Re: LF: New Eu slot 136.177 kHz?
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: quoted-printable
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org


Hello LFers !
I centred the European window of my grabber on 136.177 Khz .
If you decide to change another time , I will follow you !
73 Jean-Pierre f1afj


Le 12/12/2010 15:13, Markus Vester a =E9crit :
> Dear LF,
>
> after considerations with Scott VE7TIL, Mike G3XDV, and Laurence KL7UK,=
 I would like to discuss moving the European intercontinental transmit slo=
t. It is currently centered on 136.320 kHz, and I propose a new center fre=
quency of 136.177 kHz.
>
> This discussion was initiated by VE7TIL, who is plagued by severe QRM li=
nes, to an amount that he considers the vicinity of 136.32 kHz as being un=
usable for him. Scott believes that the interference is caused by a PLC sy=
stem leaking from a nearby powerline, and that it will probably not be pos=
sible 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 certainl=
y 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 lin=
e 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 inter=
esting to get some information how much this one actually affects the Amer=
ican 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 transm=
itter in Budapest, an idle carrier sitting at 135.43 kHz, and excursions=
 to 135.77 during FSK bursts. Normally these bursts appear every 11 second=
s, 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 foc=
us 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-d=
sl.net/df6nm/grabber/Grabber.htm with a split window, showing both the pre=
sent and the proposed new slot side by side. The direct modulation sideban=
ds (showing as red bands) are much better on the new frequency. Nighttime=
 Luxembourg QRM generally does not appear to be worse, despite being close=
r to the HGA carrier. We also expect the latter to be a more regionally co=
nfined effect, which will not be present in remote areas of the world. Aft=
er 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-E=
u 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 1368=
181.411 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 (1361=
78.157 Hz). As the frequencies are very accurate, these lines are very use=
ful calibration markers.
>
> Now, your opinions please!
>
> Best regards,
> Markus (DF6NM)
>