To: | [email protected] |
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Subject: | Re: LF: VO1NA - IZ7SLZ |
From: | Paul Nicholson <[email protected]> |
Date: | Sat, 05 Mar 2016 18:37:58 +0000 |
In-reply-to: | <[email protected]> |
References: | <[email protected]> <[email protected]> |
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Markus wrote: > Despite the fact that no carrier trace was visible in > Domenico's 0.48 mHz spectrogram ... > 1:40 UT produced a single good decode of VO1NA in South Italy Well done, I reckon that to be 5418 km. I expect that record will stand for some time. The signal was -45dB in a 2.5kHz audio bandwidth and had a dB or two to spare. I don't think it would have decoded with one second symbols. Decodes at DF6NM 2016-03-02/03: > start car. sym. offs. > UT dB dB mHz > 23:30 11.9 7.9 0 > 00:00 12.9 10.0 -1.5 > 00:30 16.1 13.6 -1.5 > 01:00 11.6 8.3 -1 > 01:30 16.9 14.2 -0.6 > 02:00 10.7 8.3 -0.6 > 02:30 17.9 14.4 -0.6 > 03:00 14.1 10.8 -0.6 > 03:30 5.7 4.4 -0.8 > 04:00 5.2 5.1 -0.8 > 04:30 3.6 4.0 -0.8 Signals look to be 10dB up compared with recent nights. We're seeing the now familiar discrepancy between Eb/N0 calculated from the carrier S/N and the BER which suggests the phase isn't very stable and these tests are probably at the limit of what can be done at MF with message durations of this length. Markus is probably right with the suggestion that there is a maximum message duration related to the propagation spreading and it is likely to be typically just a very few minutes but I wonder how it varies with distance. This achievement represents considerable effort and patience by Markus. Few of these decodes would have been successful without spending a lot of time searching for the correct frequency offset. For example a 0.6mHz offset is nearly a whole cycle of phase shift on the 752*2 second messages which is well beyond the range of the phase search of the decoder. Today I put up another 150m metres of wire here. I would have got more done but for a tendency to sit amongst the trees taking in the winter scenery in the sunshine. It is very nice to be in the woods putting up wire and only hunger and darkness forced me back indoors. -- Paul Nicholson -- |
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