As a case of last of the era, radio station JJC in Japan and 9VF in Singapore operated by Kyodo News in Japan is the last marine weather fax station which faxes daily news and navigational warnings. It is especially surprising since it is not affiliated with the meteorological agency – they operate their own fax stations starting with JMH.
One of the most important resources for those looking to receive radiofax is the list of transmission frequencies available from this guide written by the National Oceanographic and Atmospheric Administration (NOAA) of the US. This guide is regularly updated where information is available – and lists the carrier frequency (i.e. transmission centre frequency) for many fax stations around the world.
JJC and 9VF (on page 16) is listed with the following centre frequencies (tune to 1.9khz below in USB mode for white frequency at 2300hz and black frequency 1500hz):
- 4316khz at 5kW
- 8467.5khz at 10kW
- 12745.5khz at 15kW
- 16971khz at 15kW
- 17069.6khz at 15kW
- 22542khz at 15kW
- 16035khz at 10kW
- 17430khz at 10kW
The information is dated from 1999 – a long time ago – and I have reason to believe that the information may be incorrect. Radiofax services have been dwindling year-on-year, and surveys are held each year to try and gauge whether it’s worthwhile to continue operating such services. The frequencies above in bold are the ones which I have been able to hear the transmission on, although not necessarily decode a visible image.
The other frequencies which have not been bolded may be in operation, but propagation has not been favourable enough to my receiver to produce any sign of the signal.
Kyodo has a very specific signal – the slant factor in Fldigi is 0.004 for my sound card, compared to 0.012-0.015 for most other fax services, showing significant offset. The signal is transmitted in IOC576 mode with 60LPM speed (i.e. half the speed of most other fax services, taking one second per line of 1809 pixels). Faxes take hours to transmit at this rate, but at least it ensures a better quality for the delicate Japanese characters which are transmitted.
The signal transmits white tone for a while before a fax as a tuning signal, which then develops black pips which line up with the sync bar for almost a minute before the transmission. The start tone is prolonged, about five seconds, followed by regular polarity sync and then image transmission. The sync margin during the image period is black, which is inverted from the regular polarity where the sync margin is white.
So over the past few days, I’ve received a few faxes which are fairly “degraded” for quality – luckily as it is analog, it is possible to receive something even at low SNRs (~1-10dB), even if it’s just the sync margin.
In the case of fax transmissions, clarity is impacted by the signal to noise ratio, as well as the doppler multipath spreading of the signal which causes blurring at the edges and sometimes wavy/shifted faxes. As 1809 pixels are transmitted in one second (for 60LPM), a one pixel shift corresponds to a doppler multipath shift of 0.55ms which corresponds to a multipath distance at the speed of light of just ~166km!
For comparison, the distance by straight line from Tokyo to Sydney is 7822km, so the pixel time is about 2.1% path variation. Unfortunately due to the unpredictable behaviour of the propagation and height of the ionosphere, there is fading, sometimes deep and frequency selective causing horizontal noise bands, and multipath fades causing vertical lines to be doubled or jittery.
Of course, for the intended purposes of the signal, this should not be a problem, as it is intended to serve within its NAVAREA. While we are a neighbouring NAVAREA, that is no guarantee that the signal is receivable.
So here are some faxes:
27th January 2013 – JJC 22542khz ending 1956EDT (UTC+11)
27th January 2013 – JJC 22542khz ending 2040EDT (UTC+11) Sumo Match News.
27th January 2013 – 9VF 16035khz ending 2122EDT (UTC+11) Kyodo [?] News.
27th January 2013 – 9VF 16035khz ending 2226EDT (UTC+11) – missed the beginning because I didn’t have Fldigi’s non-stop mode activated, and it lost correlation. Kyodo News.
27th January 2013 – JJC 12745.5khz ending 2257EDT (UTC+11) Navigational Warnings – tuning tone, pre-sync pips, start tone, phasing visible.
28th January 2013 – JJC 22542khz ending 1824EDT (UTC+11) Fishing Chart (partial).
28th January 2013 – 9VF 16035khz ending 1824EDT (UTC+11) Kaiun-Suisan News (interrupted – Fldigi decided to “freeze” for a bit, don’t know why). In this transmission, you can just barely detect the beginning of the fax, and then the sync margins become clearer, and then the signal fluctuates … vertical banding is local interference.
And just for clarification, no, unfortunately I cannot read Japanese … but I do enjoy watching the propagation conditions visually judging by the image of the fax – and I do enjoy DXing signals, even though I’m in a noisy built up area. I had attempted to make contact with Kyodo before for QSL but unsuccessfully – so I am trying again. I would enjoy it more if I was in a radio background-quiet area ..
In 2010, I went to my Dad’s place – and using just a longwire, achieved much much better results (using MultiPSK for decoding as well). There’s no way I can do the same at my Mum’s place – even using a magnetic loop antenna to reduce interference!