Pinneberg (DDK3) HF Weather Facsimile Transmissions

I have posted before about receiving weather and shipping facsimile transmissions on HF, for a couple of days I have been using the FCDP+ and WXSat to do some decoding, also been investigating some of the mysterious RTTY transmissions you also find.

Interestingly my previous experiment was using an Alinco Scanner with SSB capability, produced better results than using the FCDP+ and SDR#. not really sure why. It appears the some processing of the audio upsets WXSat, I have tried many settings and adjustments but the decodes haven’t been brilliant clear despite the signal being very strong and clear, many of the faxs have come in with odd ‘stepping’ where portions of the image go out of sync which I have corrected in PaintShop Pro.

Any way, here is a small selection of the images I’ve decoded from the Deutscher Wetterdienst, broadcast on 7880 kHz (DDK3) from Pinneberg in Germany,

 

I think I might be mad!

I know it is difficult to believe but Spring is officially here! At 11:02 today the vernal equinox occurred.

Well earlier at 07:00 I was standing out in a snow shower with the 2m yagi monitoring the ISS downlink on 145.800MHz. This was a school contact with Australia being operated via a telebridge using an Italian ground station. Details here http://www.southgatearc.org/news/march2013/ariss_event_2003.htm

I did get a reasonable signal during the pass but sadly it was marred yet again by interference.

The weather is dreadful at the moment, the picture above shows the view out of the shack window last Sunday afternoon. I had hoped to capture various satellite transmissions but the weather was atrocious. It rained most of the day and then around 14:00 it turned into a short lived heavy snow shower.

On Monday night I went to catch the evening pass of STRaND-1 and AAUSAT3 only for it to start raining once I had got set up!

A Frustrating Afternoon

I have recently took possession a ‘new’ laptop, a nice Lenovo Thinkpad. with a Core i3 and Windows 7 Professional.

I was trying to use it this afternoon with the FUNCube Dongle and having no luck at all getting it to work! I had planned to decode some NOAA-APT transmissions and hastily reverted to my older laptop only to discover that it wasn’t receiving anything either.

In the end I traced it down to a faulty BNC coupler! I remember it was raining last time I used it and it did get slightly damp, so suspect there is some corrosion. Unfortunately by the time I had sorted it out I missed most of the overhead pass of NOAA-19.

I did manage to get two poor decodes of NOAA-18 and NOAA-15 but as you can see I was struggling with fading signals and interference.

NOAA-15 11-Nov-2012

NOAA-18 11-Nov-2012

What was interesting, and not seen before was the visible image (on the right) seems to change when it goes into darkness.

Damn you!

Some NOAA APT Decodes

Listening to the scanner this morning I heard the distinctive APT ‘chiming’ sound as one of the NOAA polar orbiting weather satellites was making a pass. It has been a while since I have done any APT decoding, so decided to capture some of the passes of NOAA-18 and NOAA-19 this afternoon.

The first two passes of both satellites were North to South around 20-30 degrees elevation, this image was the best of the them, the UK is in the upper left. 

NOAA-19 11:32 UTC 21-OCT-2012

The following passes were much higher, almost overhead, there was some interference on this NOAA-18 pass due to pagers and I got disorientated whilst hand holding 2-meter YAGI, hence the lost of signal near the top of the image.

NOAA-18 14:02 UTC 21-OCT-2012

However the NOAA-19 pass before it was much better. What is noticable is the bands of darkening, caused by nearby buildings and some large trees shielding the satellite from my the line of sight position.

NOAA-19 11:12 UTC 21-OCT-2012

All images were decoded realtime using the SDR-Radio program, received by the FUNCube Dongle connected to the InnovAntennas Yagi.

HF weather facsimile decodes

Following on from my experiments with SSTV decoding from the ARISSAT-1 satellite I decided to have an attempt at decoding some weather facsimile transmissions.

Known alternatively as radiofax, hf fax and weatherfax these transmissions were the forerunner to SSTV transmissions and are intended for marine navigation and weather forecasting. Using the short-wave HF band transmission they still enable information to be received by vessels out of range of modern internet communications. Some Japanese stations even use the technology to transmit newspaper images. More details of the technology and the history at http://en.wikipedia.org/wiki/Radiofax

These transmissions use single sideband and frequency modulation. The signal shifts up or down a given amount to designate white or black pixels. A deviation less than that for a white or black pixel is taken to be a shade of grey. With correct tuning (1.9 kHz below the carrier frequency for USB, above for LSB), the signal shares some characteristics with SSTV, with black at 1500 Hz and peak white at 2300 Hz.

It is fairly simple to decode using a computer sound card and there are many software solutions available, however most are commercial products and have severely limited trial versions. I have used the free WXFAX software, intended primarily for weather satellite decode (more on that at a later date) it can be configured to decode the FM-120 signal. Details here http://www.newearth.demon.co.uk/radio/hfwefax1.htm

Some more useful links about the broadcasts at  Marine Weatherfax NOAA broadcasts including a schedule of internal transmissions and stations (pdf) and also the German Deutscher Wetterdienst

Here are a few decodes made over the last few days on my Picasa Web Album

HF Weather faxes

From Please Ignore

To decode the signal require a SSB receiver I currently have in my possession a Alinco DJ-10X which has never excelled at HF frequencies and is very susceptible to overload and computer interference (it is more a VHF/UHF scanner) and has proved problematic in the past when using any data decoding using a sound card (suspect due to the heavily filtered audio output) but has been surprisingly good over the last few days. I am not using a dedicated HF antenna, but hasn’t been too bad since the signal is coming from Hamburg (on 7880kHz) and is fairly strong in the morning but performance falls off during the day.

From Please Ignore
 

Decoding in action

Rain, Rain go away!

>Rain

Yes, I know it a national past time to complain about the weather but really this rain is really starting to get me down. After a brief rest bite this morning and some sunshine it is raining again.

The weather station which I final set up a few months back is reporting 22mm in the last 24 hours.