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| Subject: | LF: Proposed Eu waterhole center 136.172 kHz |
| From: | Markus Vester <[email protected]> |
| Date: | Thu, 24 Feb 2011 06:14:12 -0500 |
| In-reply-to: | <e5b.b83817a.3a899eae@UNKNOWN> |
| References: | <fda.7c41c1e.3a36327b@UNKNOWN> <e5b.b83817a.3a899eae@UNKNOWN> |
| Reply-to: | [email protected] |
| Sender: | [email protected] |
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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)
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)
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