Satgen 450 Meteors,Where,When,Why by GM4IHJ (BID SGEN450) 8Nov97 Thanks to readers who have pointed out that the excellent astronomy magazine Sky and Telescope Dec97 p108, has finally recognised that meteor observation via the radio propagation properties of the ionized trails they create in the ionosphere, is both interesting and potentially far more productive than outdoor visual observation with its attendant risk of pneumonia. S+T recommends far field reception of FM broadcast stations between 88.1 and 107.9 MHz. A band also available in Western Europe. But there are lots of other useful bands if you have a suitable receiver :- Radio Amateur beacons and FM repeaters 28 to 29.5 MHz Low VHF TV Europe 48.25, 49.75, 55.25 MHz ( very hi power strong sigs) Radio Amateur beacons 50 to 50.1 MHz (24 hours a day) Low VHF TV America 56.25 MHz Low VHF FM Eastern Europe around 72.1 MHZ These lower frequency meteor scatter signals are much stronger than those at frequencies above 80 MHz and they can be received on a simple home made dipole or Turnstile antenna. Equally important :- a. You should be aware that many TV and FM station go off from midnight local to about 0600 local time. Whereas radio amateur beacons though weaker in signal strength stay on 24 hrs/day as do a few TV stations. b. FM stations overlap in frequency. You can get 3 or 4 stations in different parts of Europe all on the same frequency . So using FM stations for meteor flux rate counts is suspect. c. Radio listeners using audio reception , hear far more meteor signal echoes than visual observers see visible meteor trails. The smallest dust grain contains millions of atoms which when ionized in a collision with the atmosphere produce excellent reflection and forward scatter of low VHF radio signals. Indeed if you try echo counting in a big shower like the January Quadrantids, the August Perseids or the Leonids (1100 to 1300ut peak) 17 Nov , you will find the echoes coming so fast they overlap into a continuous tone. To counter this wall to wall effect the IHJ station DX TV was left tuned to 48.25 MHz and actual locked TV pictures were counted in order to discern when shower maximum occurred (BWTV bandwidth to audio rx bandwidth gives about 100 times reduction in observed echoes which makes maximum timing clearer) d. However times change, and starting with the 96 Leonids the IHJ shack features a dipole feeding a Drake R8E rx sending audio 2.7 kHz wide to a sound card feeding AF9Ys excellent FFTDSP software. This allows continuous observation and recording of a low VHF spectrum in 2Hz channels over 2.4 KHz , in a band tuned 48.252 which covers 4 TV stations, on different frequencies in Denmark, Sweden , Germany and Spain, permitting simultaneous records over 140 degree arc of bearing. e. But you do not have to wait for big showers. Every morning 0600 to 0900 local time your part of the earth is running into the paths of ancient comet dust streams which provide the bulk of meteoric material. You must of course ensure the TV stations of your choice are on the air ( furthest east, soonest on) Then once you know the regular performers you can enjoy meteors with your breakfast, every morning, rain or shine, cloudy or sunny, dark or light.