Introduction & Equipment Required

We are dealing with APT (automatic picture transmission) in this section as it is by far the cheapest and easiest way of receiving satellite images.   We will hopefully be covering other types of satellite transmissions in the future.

For those who have never seen an amateur weather satellite image before click here.

These satellites are polar orbiting so travel around the earth in a north-south or south-north direction all day every day. There are American (Noaa) and Russian (Metor,Resures) satellites. You should expect to receive 3-6 images each day depending on your location. If you have never received an image from a satellite read on and learn how.
 

Equipment required

Receiver
Sound blaster compatible sound card
External Antenna
Computer
Software
Other bits and bobs

Receiver

Much against popular belief a scanner can be used to receive these images.  The difference between a standard scanner and an APT receiver is that the bandwidth is wider. Commonly on a scanner it is 15-25 Hz and on a satellite receiver it is closer to 50Hz. This will affect the results that you would expect to receive but if you already have a scanner why spend any more out on a hobby that you may not enjoy?

The frequencies that you will need are:

There are a couple of others but they rarely transmit over the uk.
 

Sound Blaster Compatible Sound Card

Pretty straight forward. One thing is make sure that it works correctly,  i.e. drivers are up to date and there is a facility for either a line in or mic in connection. Unfortunately one of the many things with soundcards you can hear the sound through the speakers but due to the way they work the computer may not be sensing the sound.  Always remember to check your settings.
 

External Antenna

This is very important as satellites transmit at very low power levels and a well placed antenna is an important part of imaging. I use a wide band discone picked up for less than 20 pounds at a rally and this does a remarkable job in my eyes. You can get dedicated antenna and these will be mentioned in a later section.

Computer

If your reading this I will assume that you possess a computer of a reasonable standard so no more to say here other than if its higher than a 486 with good hard disc capacity you should have no problems here.

Software

There are two vital pieces of software you will need. The first being a satellite tracking program so you know when the satellites will be over your location.   I use Les Hamilton's Footprint (download from here) and I will discuss the set up a little further on in this article.

The second programme is wxsat (download from here).  This program enables you to see the sound received turn into an image. As before this will be discussed a little later in more detail.

Other Bits & Bobs

The only other piece of equipment is a lead from your scanners head phone socket to your sound card. These are only a couple of pounds and will be useful for other types of decoding not just satellites.

Sound & Satellite Tracking

The first thing to do is check that the computer can record a sound file do this by connecting a lead from the headphone socket on the scanner to the mic in/ line in connection on the reverse of the PC. The fastest way to check I find is to open a programme called sound recorder.

On windows 98  Start, Programs, Accessories, entertainment, Sound Recorder.

Find any active signal press the record button stop after a few seconds and then play (don't forget to turn the scanner down at this point) If you hear what was just being transmitted great if not double click the speaker bottom right of your desktop and check the settings.  There is a help section built into Windows so I'll let you all work it out.

The second part is to find out when a satellite is passing over head.   For this I use footprint and will explain the basics of how to use it.

With satellite prediction you need information called Keplerian elements these can be downloaded from the web from here (click keps then kepele.zip you will also need an unzipping programme such as winzip).

When these have downloaded unzip them to the same folder as footprint - normally C:\footprint.
Now double click the footprint icon and up pops the programme. Don't panic its not that complicated I promise.  A screen shot from Footprint :

First thing to do is set your location (Top Left click File, Set defaults) and time settings not forgetting to make sure the daylight saving button is pushed to ON for those in the UK. The only settings you should change are Latitude, Longitude, Location, and to check the time setting are correct for your part of the world (Chelmsford Longitude is 51.5 degrees North, Longitude is 0.5 degrees East).

Next you need to set the recently downloaded kepelers into the programme. Click File, load 2 line file. Then choose Kepele.tle file and ok. Then push file again and press save default element set. This just saves those kepeles as the ones it should work from each time you open the programme up. Please note that to make sure your predictions of satellites are correct kepeles should be updated at least once a fortnight.

Last of all we need to pick the satellites and see where they are in relation to our location. Click Satellite and scroll down to it and left click on the satellite you wish to track. At the bottom of the screen under the map you will see boxes with sat1-sat8 in them double click on one of those and it should have changed from sat# to the satellite you picked from the list. At the same time on the map an icon should have appeared with the same name and a ring around it. You can have up to 8 satellites on the map at once so repeat the above few steps for all of them if you like. To find out when they will be over your location click AOS/LOS and then list by time. If all is well you should see some thing like this.
 

If not and the box is blank make sure the satellite button and the bottom of the page is depressed/highlighted.  If you do have any major problem there is an excellent help file built into the program to get you started.

What does it all mean?

Column 1 This is the Acquisition of Signal time (24 hr clock) Tells you when the satellite will start its pass over your location.
Column 2 Time in Minuets telling you how long the satellite will be in range of your location.
Column 3 Maximum elevation with the best being 90 degrees.
Column 4 Which direction it will be travelling over your location S=South-North and N=North to south
Column 5 The name of the satellite

At this point I recommend you wait until a suitable elevated pass is available to you above 50 degrees which I find is best and tune to that satellite's frequency and listen for it.  It should sound like this.

Don't worry if it isn't all that clear and don't be suprised if you hear pagers break through - it comes with the hobby unfortunately.

Once you are aware of what you are listen for we can go ahead and set up Wxsat for reception of the signal.

Reception and Processing of an Image

Once you are aware of when a satellite will be over head we can go ahead and set up Wxsat for reception of the signal.

The most simplest way to decode an image with this software is to do the following.  Wait until you can here the signal and then making sure the lead from the scanner to the computer is connected correctly and that sound is getting through ok.   To double check press 'recording' on the top bar then 'test'.  You should see a black box with a green (hopefully) fluctuating line inside.  Make sure this is within the top and bottom horizontal bars.  If not, turn the scanner's volume down and if too low turn the scanner's volume up a little.  When you are happy press 'recording' again and then 'stop'.

Now that we're sure the sound settings are close, it's time to receive your first image from a satellite.
I find when using a scanner, the programme doesn't always detect the signal properly so by doing the following you can manually capture an image. Also you should have the squelch fully open on your scanner.

Press 'Parameters' (don't panic all will become clear later) and then click #8 No Data.  Then press 'Recording' and 'Picture and wave file'.  It will ask you what you want to call the recording and where you want to store it.  Fill in as necessary and click 'ok'.  Your mouse pointer will go into thinking mode and the only heading highlighted is 'recording'.  When you can hear the satellite signal press 'recording' and then 'manual sync'.

Sit back relax and wait, don't worry if the image is angled or of poor quality just relax and wait until the signal is no longer present.  When its finished (depending on location anything from 6-12 Minutes should be expected on a 14 minute 50 degree+  pass) press 'recording' and 'stop'.

Now comes the more technical but most rewarding part.  Looking at the screen it probably looks something like this.  This image was taken using an Aor AR8000 with a Discone.

If it is a Noaa satellite it will have tried to decode two images side by side, the worse one will be the infra red.  With a scanner this is very difficult to receive.  On Meteor or Resures their will only be the visible image present.

Now we need to get it correctly oriented and straightened up, if the image obviously contains very little then it should only be a short wait until another satellite passes over.

Press 'File' and then 'wave input' and choose the recording you just did, click 'ok'.  Back at the main screen click 'parameters' and 'decoding'.  In front of you should be a box like this:

It look horribly complicated but we only need to change three settings here to straighten and orientate the image properly.  I have marked the three important ones with colours.

The Red box.  If you look at this and it says as above N-S (north-South) and you know the satellite passed over you travelling South-North, just click the arrow down and pick S-N.  Ignore the one with a star next to it in this pop down list.

The Blue box.  This changes the orientation of the image.  To make my images straight I have it set to 2399.650.  You may need to experiment to get the right settings for your computer.

After each change of this setting, press 'ok' then go back to file and press 'Start Processing'.  Then press 'file' again and 'manual sync'.  You should see the image re-decoding on the screen and after a few changes of the blue box it should be straight.

The Green Box.  This adjusts the amplification of the image, the higher the number the brighter it will be and the lower the number the darker the image should be.  Hopefully you wont need to use this too often if the sound settings are correct.

When you are happy with the brightness and orientation of the image it may well not start at the left of the page. If this happens press 'Edit', 'Correct X' and your pointer should have turned into a line.  Place the line on the part of the image you want to the left and click.  It should now look something like this and even a little straighter if possible.

The visible part of the image is on the left.

Congratulations you have decoded your first satellite image.  To save press 'bitmap', 'save as'.  You can then view and edit the image in a picture editor.

Don't worry if its not to impressive as you first thought it would be.   It is difficult to get good results with a scanner but be patient and if you take a fancy to the hobby, join a mailing list for enthusiasts were you can ask questions and get advice from people all over the world.

satellite imaging email list (just send blank email to the link) or have a look at the Remote Imaging Group website.

There are plenty of ways to improve the set up such as a dedicated antenna and receiver and the above groups will be able to assist you in further exploration of this hobby.

For some of the best received images in the uk have a look at Peter Tanner's site.

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