The image below represents a part of the audio spectrum from the output of the NLO radio receiver which is tuned to 143.050MHz. On this frequency is a very powerful satellite radar which is located in eastern France, close to Geneva, operated by Onera.


TOP: Norman Lockyer Observatory, Sidmouth, Devon, UK
BOTTOM: Andy Smith, Tavistock, Devon, UK

UPDATED ONCE PER MINUTE (WHEN OPERATIONAL)
 

Data plots (G7IZU)
Top graph: meteor counts per hour
Bottom graph: ping durations (secs per hour)


 


When a meteor enters the atmosphere at a location somewhere between the transmitter and receiver at 80-110km altitude, the meteor's ionized trail reflects the radio signal for a brief moment. The signal appears as  quick "ping" of sound from the receiver which is rapidly descending in frequency, due to the Doppler effect. It is not the direct sound from the actual meteor. The image is updated once per minute and time flows from right to left. It shows approximately the last 2.5 minutes of reception. The different colours represent the strength of the received signals.

The Norman Lockyer Observatory is located at Sidmouth, Devon, UK.

Links:
NLO Homepage
G7IZU RRD Website (live page)
Download a Powerpoint presentation  - how the system works (requires at least a Microsoft Powerpoint 2007 viewer)