Our guest speaker, Nick Read - G7DND/M5DND provided us with excellent live demo of meteor detection. The timing of this meeting was particularly critical as it occurred within the Leonids meteor shower. This is a predictable event as the Earth passes though the tail of the Temple Swift comet every year. Under clear and moonless conditions, the shower can be observed with the naked eye, although a full moon would have made observation quite difficult on this occasion.
Nick was able to demonstrate a method of detecting the reflected signals originating from a couple of very convenient East European 50MHz TV transmitters. The receiving antenna was a simple 6m Delta Loop, strung up just outside our clubroom. The reflected signal could be detected audibly in the 6m band as a series of tones lasting from a fraction of a second to several seconds. In addition to just hearing the tones, Nick was running some software on his computer that was providing a visual representation of this event.
As each meteor burns up in the earth’s atmosphere, it leaves an ionised trail behind it. There is also an ionised area around the meteor itself. The graphical image Nick had displayed showed each meteor as a straight line and if Doppler shift has been detected, the line started as a curve before straightening out. This particular software can also keep a log of the strikes, so the station can be left unattended for many hours if necessary.
The second demo of the evening was meteor scatter. Nick had set skeds with two stations, one in the south west of England and the other in Poland. The plan was that both stations were to put out a series of calls for Nick between 2100 and 2115 gmt. One station was to call in the first half of each minute and the other was to call on the second half of each minute.
Detection of the signals was made possible by using WSJT4 software by K1JT. (WS = ‘Weak Signal’). The designated time came and we all watched the screen for signs of recognisable call signs. Several minutes passed, but then we saw G4PCI (the west-country station) along with Nick’s call M5DND. Unfortunately no luck with the Polish station.
Finally, it’s worth noting that most meteors range in size from a grain of sand to a small pebble. The vast majority of those that enter the earth’s atmosphere, burn up long before reaching the ground!
Many thanks to Nick for coming along to Sutton & Cheam. It was a very enjoyable evening. Nick doesn’t drive, so we’d also like to thank Steve - G1LJR for providing the transport.