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

More SSTV images from space

After the success earlier in the week have been trying to get some more images from ARISSAT-1 as it passes near or over the UK during the evening. However reception hasn’t been quite as good.

The signal has been dreadful and the passes have been very short lived, not sure if it is the satellite’s performance falling off, interference or just bad luck. The only really decent image I got was another of the project logo. Really would so like to get a decent image from one of the on board cameras, had one almost image but far too much noise to make anything out.

8 years ago – UK139-L

The other day while hunting around for a home made programming cable for my Alinco DJ-X3 I found this odd looking box hiding in the bottom of a drawer

It is an eQSO/Echolink PC interface which I built 8 years ago when I set up a PMR446 eQSO Internet Gateway. The Gateway which was designated UK139-L was short-lived mainly due to the fact no one ever used it and it required a dedicated computer running 24/7.

My recollection of that period is a little vague but licence free PMR446 two-way radios had been around since 1999 and around 2003 was when they officially replaced the Short-Range Business Radio (SRBR) service and had become more mainstream and a lot of hobbyists saw them as a replacement for CB radio. Shops like Argos had started selling them to the general public (many of the dog agility shows I attended used them for across site communication).

Obviously being a geek interested in radio I decided to get some and when I found out about the scheme to connect gateways using a VOIP system to allow people to talk all over the world I couldn’t resist. With my usual enthusiasm I set about building one, testing it by driving around the local area and even created a website on the now defunct Geocities.

I will have a backup of the website somewhere, but as it turns out it was one of the pages archived by the Geocities.ws project. I have downloaded it and mirrored it on my current website at UK139-L Newark-on-Trent Some of the internal links are broken (not sure what version was archived) but I will fix it in the near future.

It has been years since I last looked at PMR446 but it seems the original website that coordinated the whole eQSO pmr446 project www.446user.co.uk has shut down and the official eQSO project appears to have reverted back to be just amateur radio based. However there appears to be an unofficial eQSO PMR network and an alternative in the form of the Free Radio Network

I will have to do more research and perhaps even resurrect the gateway when I get around to kitting out the shack.

ARISSAT-1

It has been nearly a year since I last posted, and what a year it has been.. but I digress.

Still tinkering with my radio scanners when I get the chance and over the last few days have been satellite hunting.

The ARISSat-1 amateur radio experiment was manually deployed on 3rd August 2011 from the International Space Station during EVA 29. Following on from the earlier SuitSat experiment ARISSat-1 was designed, developed and tested by AMSAT-NA and ARISS volunteers. It’s primary mission is STEM (Science, Technology, Engineering, Mathematics) education around the world.

The idea of the satellite is students should be able to easily receive the 2m FM transmissions as it fly around the globe and use the information in classroom exercises. The transmissions consist of voice message, SSTV images, telemetry and CW beacons.

Certificates will also be issued for SSTV image reception, voice and telemetry reception, CW reception, full SSB telemetry packet reception and Kursk experiment reception. The satellite has four cameras on board that will constantly be taking pictures and sending them to earth using SSTV Robot-36 format in the 2m FM transmission.

The official Web site for the ARISSat-1 project is arissat1.org .

Well I decided I would have a go and using my Realistic PRO-2006 scanner and my homebrew wideband antenna up in the loft have spent the last few evenings trying to pick up the transmissions as it heads over the UK.

The best reception so far was on the 21st August during the second pass of the evening where I got a decent amount of voice transmission and was able to decode a frame of SSTV (pictured above). I put the audio up on to soundcloud.com as well as youtube.

ARISSAT-1 21 Aug 2011 by nerdsville

Unfortunately the satellite has suffered some problems with it’s on board battery and goes silent/resets when it enters the shadow of the earth, which is problematic for reception in Europe as the current passes are occurring late evening.

There are a couple of decent passes this week, so hopefully can get some more intercepts and maybe decode some telemetry using a borrowed Alinco DJ-X10 which has SSB mode. Pass details for your location can be found here