Radiofax: SVJ4 (Hellenic National Meteorological Service, Athens Marine Meteorological Centre, Greece)

Continuing on my radiofax expedition, I thought it would be best to try looking for another station I had never heard from home, hoping it would still be alive. In this case, it is SVJ4, operated by the Hellenic National Meterological Service of the Athens Marine Meterological Centre, Greece.

According to the NOAA/NWS Radiofax Schedule, SVJ4 operates two frequencies – 4481kHz and 8105kHz. During one day using the UTwente WebSDR, I thought I’d tune in to see whether there was any action – the UTwente receiver is normally pretty good at picking up anything in Europe. To my surprise, I was able to hear the signal on the latter frequency, but even more surprising was that the published frequencies were the SSB tuning frequencies and NOT the centre frequencies which would be 4482.9kHz and 8106.9kHz respectively. Perhaps this should be fixed …

As a result, I recorded the signal from WebSDR (to avoid the “twente wobble” due to adaptive resampling) and decoded it with Fldigi, choosing the best faxes over the period of a few days to showcase below. Note that the faxes below represent a snapshot in time and are not up to date. None of the following charts should be used for navigation. Copyright in the chart contents remains property of the sender, in this case, the Hellenic National Meterological Service of the Athens Marine Meterological Centre, Greece. The provision of the images below serve as documentary evidence of the station’s transmission characteristics, format of the content distributed and as evidence of the station’s activity.

Faxes

The faxes were received via WebSDR recording, with the charts presented in their transmission order but excerpted from decodes made on different days of January 2019. As the WebSDR does exhibit audio discontinuities under network stress, some of the images were altered in Photoshop to restore their alignment which may result in slight alignment discrepancies and corrupted lines. SVJ4 operates in a “block” arrangement, starting up at around 0845UTC and sending charts throughout to around 1100UTC, making it easy to receive in a sitting. The schedule from the NOAA/NWS schedule is mostly correct with only a slight exception.

The first chart is a surface analysis, as expected. It shows the SVJ4 transmission characteristics quite clearly – a relatively short start and end tone, short phasing period, a continuous gradient bar from white to black just prior to the chart and sending of charts in the landscape orientation (shorter transmission time). The chart also features a geostrophic wind scale in the corner, with annotation text in the top left corner. The gradient bar is prefixed by three letters, SWA. The margins of the image are white in the image period, with this showing quite strong similarities to HSW64, the station operated by Thailand, which might be using the same equipment and also publishes the SSB tuning frequency rather than the centre frequency.

A deviation from the NOAA/NWS schedule is made here, as the surface prognosis is for +42 hours.

This is followed by a surface prognosis for +66 hours, whereas originally in 2007 this would likely have been +24 and +48h respectively.

The four charts that follow the surface prognosis are the HNMS WAVE model charts which show wave height and direction for +30, +36, +42 and +48 hours. This first set is for the Mediterranean Sea.

This is followed by the same four charts, but instead for the Agean Sea.

Conclusion

It was a surprise to see another station I had never received before and the charts that were sent. SVJ4 is a simple station sending all the charts just once a day in a “block”, but this makes it easy to observe. It probably uses similar equipment to that used by HSW64 (Thailand) as they both advertise the SSB tuning frequency rather than the transmission centre frequency, and both feature white-to-black scale bars with letters on the left. All charts sent from SVJ4 are rather consistent in labelling, orientation and appearance, which is a little boring. But at least my curiosity is somewhat satisfied and it’s good to see it’s alive.

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2 Responses to Radiofax: SVJ4 (Hellenic National Meteorological Service, Athens Marine Meteorological Centre, Greece)

  1. Frank says:

    Hola Gough, thanks for the excellent series on HF radiofax. I am a frequent ie daily user of fax services when afloat. A comment on carrier.v.assigned frequencies ‘but even more surprising was that the published frequencies were the SSB tuning frequencies and NOT the centre frequencies which would be 4482.9kHz and 8106.9kHz respectively. Perhaps this should be fixed …’

    Interesting that there is that glitch in the listing… maybe a note to NOAA is in order.. email addys can be found down the bottom of the NOAA PDF as can the addy for the Hellenic Met Office.

    This is from the NOAA site http://www.nws.noaa.gov/os/marine/rfax.pdf

    ‘Unless otherwise stated, assigned frequencies are shown, for carrier frequency subtract 1.9 kHz. Typically dedicated radiofax receivers use assigned frequencies, while receivers or transceivers, connected to external recorders or PC’s, are operated in the upper sideband (USB) mode using carrier frequencies.’ Very hard to explain… best to just accept it for what it is :).
    Cheers,
    Frank

    • lui_gough says:

      No no – indeed, I understand completely the difference between the USB dial frequency (which is designed to centre tones at 1500/2300Hz for WMO style fax receivers) and the centre frequency of the emission (so the data swings the carrier +/- 400Hz either sides), hence the comment that the listing did not note the caveat, because if you notice the HSW64 listing in the rfax.pdf has a * to denote that it (might be) the dial frequency instead (and indeed, it is in the case of Thailand HSW64).

      I have tried to send NOAA/NWS an e-mail previously for a completely unrelated reason – a posting about this shortly – but lets just say that due to the US Government Shutdown, it seems they will take a while to get around to addressing e-mails sent to them.

      – Gough

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