Simple system for Monitoring Weather Satellites    




So you have decided you want to receive the NOAA and Russian METEOR orbiters and you have a radio that receives 137.500 MHz and a computer. So now what do you do? I hope this short dissertation will steer you in the correct direction.RIG can supply many of the items required for DIY applications. Please check out the › links ‹ page for commercial suppliers ... 



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Weather satellites fall into two main categories:

  • Low Earth Orbit (LEO - Polar APT) satellites

  • Geostationary Earth Orbit (GEO -Geostationary WEFAX ) satellites

Polar APT

Mostly enthusiast start by receiving images from the `Polar orbiting satellites', which transmit Automatic Picture Transmission (APT) signals in the 137MHz band. Current satellites include the American NOAA series and Russian Meteor or Sich series. These tend to be sun-synchronous, with two orbits passing at or near overhead at the same times each day, 12 hours apart. APT resolution is about 4km per pixel and two channels are usually transmitted, Visible and Infra Red. 


WXtoImg Sample Images

A few of the many web sites updated continuously using WXtoImg:


The 137MHz band is a fairly easy band in which to build your own equipment and is relatively inexpensive as a band to start with. Provided you own a PC then it is possible to get started receiving APT signals for a little as Receiver kit and antenna for less than 130 EURO, by using shareware to decode the signal, using the power of your computer sound card. 


Geostationary WEFAX 

The next stage tends to be reception from one of the geostationary satellites over the equator e.g. Meteosat 7 on the Greenwich Meridian , GOES East & West over America, Meteosat 5 over the Indian Ocean and GMS the Japanese satellite imaging over the Far East. These satellites transmit two kinds of images, namely High Resolution digital (HRI) and analogue (WEFAX). The easiest of these to receive is the WEFAX signal, which is transmitted in the 1.69 GHz range. HRI data reception, mainly intended for Primary Data User Stations can involve having to puchase a special key to decode the encrypted signal

WEFAX images can be received either using a prime focus dish linked to a 1.69 GHz receiver or it is possible to use a off-set dish (ex Satellite TV type) with an active feed, linked through a downconverter connected to your existing 137MHz polar receiver. For those with site difficulties, then both a long yagi or there is even a small 9 inch (22.5cm) micropatch flat antenna available commercially at at approximately 120 Pounds Sterling, can be used instead of a dish.

LEO weather satellite signals can be received on various frequencies in the 137 MHz band. The US NOAA satellites use 137.500 and 137.62 MHz. The Russian Resurs/Meteor satellites use 137.85 and 137.30 MHz. These frequencies are for the APT (Automatic Picture Transmission) signals (sound like a series of "pings"). Beacon signals from the NOAA satellites (sound like a very fast light "buzzing") can be found on 136.77 and 137.77 MHz.

LEO weather satellite signals can be received on various frequencies in the 137 MHz band. The US NOAA satellites use 137.500 and 137.62 MHz. The Russian Resurs/Meteor satellites use 137.85 and 137.30 MHz. These frequencies are for the APT (Automatic Picture Transmission) signals (sound like a series of "pings"). Beacon signals from the NOAA satellites (sound like a very fast light "buzzing") can be found on 136.77 and 137.77 MHz. 

The National Oceanographic and Atmospheric Administration (NOAA) has launched several satellites of the TIROS class. Russia has its own weather satellites in the Meteor class and China has launched weather satellites known as "Feng-Yun". The LEO weather constellations of the United States and Russia provide an easy reception target. The APT (Automatic Picture Transmission) signals transmitted by these satellites are very strong and distinctive. 

An APT signal can easily be distinguished by listening for the timing tone which is transmitted at a rate of 2 "beeps" per second. Each timing beep represents the start of a sweep of the scanning radiometer on board the spacecraft. A motor in the scanning radiometer provides the horizontal sweep, and the motion of the spacecraft through the sky moves the field of view to the position of the next sweep. As the spacecraft moves along its orbital track it therefore builds up a picture in much the same way as does a domestic television receiver (but with a resolution of 120 lines per minute). Between each timing beep is the modulated data for visible and infra-red images of the terrain beneath the spacecraft..

The NOAA beacons are quite a bit weaker than the APT signals. The transmitters are one Watt as opposed to 5 watts for the APT, and the beacon antenna is a small omni design as opposed to the beefier QFH for the APT downlink. The beacons are also switched off from time to time if there's a conflict with one of the other "birds". NOAA 11, for instance, is still actively collecting a limited amount of data even though the imager is kaput. During certain times the beacon on NOAA-14 is switched off so that the Fairbanks and Wallops stations can get some of the routing "housekeeping" data down from NOAA-11. The same holds true for NOAA-10 & NOAA-12.

If you have suitable receiving equipment (Receiver RX-137-141MHz) you can easily display APT weather pictures on your own PC. 

GEO satellites remain in a fixed position in the sky, and are usually less interesting to monitor unless you are interested in decoding weather picture signals.

For detailed reception data on LEO and GEO weather sats, you should consider subscribing to the WxSat ( Polar orbiting status report or ) mailing list..

To display a picture from the orbiting birds you need several things. First you need to 'acquire' the satellite. This means you need the program to calculate its position at any time and determine if you can hear the signals from the 'bird'.

The best place to get this program is probably WXtrack (Copyright © David Taylor, Edinburgh.). WXtrack has four screens, Setup, World Map, Ground Track and Flight, which are accessed by means of a tabbed page control. On first running the program, you will be presented with the Setup screen, although in normal use the World Map will be the first to display with a real-time presentation of your chosen satellites.

After you have acquired the program and have it running on your computer, you then need the Keplerian Elements for the NOAA satellites. These elements as well as some tracking programs are available from the NORAD Two-Line Element Sets Current Data ( ) If you use Keplerian Elements more than 3 or 4 weeks old, your chances of hearing the bird are reduced.

Once you are tracking the birds you should hear them on your receiver.They will be on 137.62 (NOAA-17), 137.500 (NOAA-15), 137.850 (Meteor 3-2), 137.4 (Meteor 2-16), 137.3 (Meteor 2-17 and 2-18). Now comes the first thing different about NOAA orbiters. The frequency deviation of the FM transmission is about +/-18-20 kHz. This is 4 times the normal deviation of a police call (NFM) and 1/3 the deviation of the FM broadcast band FM signal (WFM). If you receive the signal on the regular communications width of the scanner the light areas of the picture will be noisy and the signal will sound distorted and the picture will basically be useless. If you use the FM broadcast bandwidth (assuming your scanner will let you), the signal will be weak and there may be too much background noise to see the picture.

So what now ? Well there are two ways to fix the problem, find a receiver with the proper I.F. bandwidth filter of 15 kHz (NFM), or modify the I.F. of your scanner to about 30- 50 kHz. The simplest mod which has been found to be workable is to remove the narrow communications I.F. filter and replace it with communications I.F. filter 30 kHz . This provides for good Wefax pictures from GOES and pretty fair NOAA orbiter pictures. It can of course result in retuning the radio, voiding the warranty and making the squelch not work properly.

The other characteristic of the NOAA satellite transmissions is THEY ARE WEAK. To get good pictures over a large area we have found a pre-amplifier to be essential. A GaAs-FET type can be obtained from various sources at a reasonable price but still about 50-100 dollars. You can also build one for about 25 dollars from plans for a pre-amp for the 2-meter amateur band and tune it to 137.5 easily... 

Lastly, but importantly, the antenna can be of an omni directional, uniform pattern type such as a turnstile antenna similar to those used in the FM broadcast reception business but of course tuned to 137.5 MHz. Mount the pre-amp at the antenna if possible... 

Now that you have a nice audio signal from the satellite, what happens next? The audio tone of 2400 HZ which is the carrier tone that is used to carry the picture information (video), must be detected and the video data converted from analog to digital and then displayed on the computer monitor by the software. The hardware (soundCard) and software (JVComm32) to do this is available from several sources with more coming along. Several stand-alone boxes are also available that produce some form of computer output either in printed form or on the display... 

One of the best sources for information is the WEATHER SATELLITE HANDBOOK available from Dr. Ralph Taggart of Michigan State University at 602 S. Jefferson, Mason, MI 48854 for $15.00. Taggart also writes the monthly WEATHERSAT column which appears in '73 Magazine. A must is the Journal RIG ( Remote Imaging Group ) - which is published quarterly... 

At the present the simplest software for thePC IBM (OldTimer MS-DOS :-) is the JVFAX 7,1a (Eberhard Backeshoff, DK9JV) software. A hardware kit is available from EMGO which includes the video dectector circuit and A/D converter. Input to the PC is via the COM port. If you want to build your own, complete documentation to build an interface circuit on an IBM PC prototyping board is available from M. Gola - EMGO, for $6.00 - EasyInreface... 



[1] - ANTENNA (Turnstile or QFHA)

[2] - PRE-AMP 137 - 138 MHz

[3] - RECEIVER 137 - 141 MHz

[4] - IBM COMPATIBLE PERSONAL COMPUTER (minimum requierement:Pentium 133 MHz/RAM64MB/HDD 1GB/WIN-95) 


[6] - CAPTURE SOFTWARE (JVComm32 , WXtoImg , MultiFAX , WXSat ,   Sky-Eye ) 





[1] Ó RIG

[2] Ó 

[3] Ó MultiFAX 


LINKS TO OTHER WEFAX ENTHUSIASTS (Some Interesting and Useful Weather Satellite Links)

Satellite Hot report - satellite informations, news and documents from satellite world

David & Cecilia Taylor's Web pages - Over Christmas 1998 I decided... 

Enrico Falconelli and Roberto - HRPT specialists and construction

Benvenuto nella Home Page di Valter Medri - daily updated Pictures from NOAA and METEOSAT images of Italy

F1AGW Jean-Louis - Comment les informations et les images météorologiques sont transmises et comment les recevoir

Jacques Gentil´s pages   daily updated Pictures from polar orbiting satellites over the Mauritius region

De kunstmaan groep from Joop Meijer

Nobuhiro Kajikawa  HRPT images.

Paul Hayes  QFH antenna

Julian Moss G4ILO software and details of  interface for the RX2 receiver.

Otso Laakso, Finland with a image archive which include all his colorised NOAA pictures since 1997.

The KB8UKP Amateur Radio and WXSAT Page

Jess Urban -KCOBYF - Automatic Picture Transmission Images

University of Cordoba, Argentina NOAA and Meteor images of South America

Michael Pedersen (Denmark)   pcb construction, and information

Hartmut Schaksmeier (Germany)

Mike Dunn´s Web Page (Tasmania)

Laura Halliday´s VA3LDH Web Page

Jim K2TL using WXSat .

Peter Tanner´s Web Page JVFAX masks for downloading

Archived Pictures from Noel

Mika Iisakkila Weather Satellite page from Finland

Steve Blackmore Weather Satellite page

Ian Busby Weather Satellite Image Homepage, using WXSat

Kevin´s Weather Page

Kevin Bates Weather Site

Milan Konecny VE3NZK using WXSat

Salvador Esteban Munoz EB3NC, Barcelona Spain using WXSat 

Les Hamilton Weather Satellite Image Pages, free software and using WXSat 

ON4KGV Gustave The following pages are dedicated to weather satellite imageries   

Bob Cash Daily weather satellite images (received in Fountain Hills, Arizona, USA)

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