Over the last few days I have been increasingly fascinated the phenomenon of Meteor Scatter. The last few days have been filled with the Perseid Meteor Shower which means there was plenty of Scatter to observe.
Before I dive into the work of Amateur Radio Meteor Scatter I wanted to observe it using equipment ANYBODY can get and use. Using a simple SDR receiver and a small beam antenna I was able to receive the signals.
For Signals to be scattered in the first place. There first needs to be a transmitter sending them out. Amateur radio operators have their own transmitters which are used to talk to other amateurs but for those with the equipment mentioned above it is a lot easier to make use of a transmitter that is a lot more powerful.
GRAVES Radar
In the south of France is a RADAR system developed for tracking Satellites and other objects in Low Earth Orbit. It is known as the GRAVES Radar, (French: Grand Réseau Adapté à la Veille Spatiale). With the transmitter being located on a decommissioned airfield near Broye-lès-Pesmes at 47.3480°N 5.5151°E and the receiver at a former missile site near Revest du Bion on the Plateau d’Albion at 44.0715°N 5.5346°E.
The transmitter and receiver are approximately 226 miles (364.34 km) apart this is because the receiver cannot receive the transmitter directly otherwise it would block out the reflected signals it was trying to receive.
The transmitter sends out a CW signal with a power many KW on 143.050MHz. I have not been able to find a confirmed source of the official power output it’s probably classified information. More information on the Transmitter can be found here.
Receiving the reflections
As a meteor zips through the atmosphere and burns up it leaves an ionised trail behind it in the E layer of the atmosphere. This trail is what then reflects the RF signals transmitted by the GRAVES radar transmitter. Because the trails are so high up this reflected signal can be received for miles and miles around.
Pointing your beam antenna in the direction of the transmitter and connecting your SDR receiver to your PC and using some SDR software with a water fall (I Use SDR#). Set your mode to USB and tune slightly below the transmitter frequency of 143.050MHz. you may need to zoom in on the waterfall so only a few hundreds of hz are showing.
You should then start seeing blips appearing in the waterfall accompanied by the brief tones. Theses are the smaller fragments that burn up very quickly. Leaving only small trails that disappear quickly.
But sometimes there will be a larger meteor which lasts for a number of seconds before being completely burnt up. These leave a longer trails which take longer to disappear meaning the reflection exists for longer. This will give a longer tone and streak in the waterfall.
Below are a few screen recordings I have made. These are live recordings and so there are some periods of silence.
If you are closer to the transmitter then you may also experience similar phenomenon cause by Aircraft. This is un-ironically known as Aircraft Scatter. And then also satellites if your setup is large enough. It is possible to see longer trails created by the ISS (International Space Station) for example. These will have a doppler effect applied to them meaning the reflected signal will appear to change frequency over time. This is because the object reflecting it is moving.
If I ever manage to achieve this then I will update this post with examples of it.
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