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Re: (meteorobs) eta Aquarids, strike one
>>I'm wondering if contributors to meteorobs who have experience with simultaneously observing meteors visually and with, say, a car radio, would be so kind as to share that experience with me. What percentage of visual meteors have an audio counterpart, and vice versa. <<
Hello Bruce....during the mid 1990's, I did a lot of simultaneous recording meteor data visually, while monitoring reflected sounds from meteors over a couple of the fm freq bands. It's been a while....but it seems to me that I would routinely see, as well hear a signature simultaneously with about 1/5 of the visual meteors.
>> In the case of matched sets, what is the preferred direction to look and listen relative to the radiant? Relative to the distant FM transmitter? <<
Usually the very bright meteors would produce a radio signal no matter where in the sky it occurred. On some nights, I experimented by pointing my yagi antenna straight up and still picked up a significant number of simulatenous meteors. I only pointed my antenna straight up a few times, mainly out of curiosity. But I'd usually leave my antenna pointing the same direction every time, to monitor the same distant fm transmitting station. I was in Descanso, Calif. about 40 miles east of San Diego. The transmitting station was in Phoenix, Arizona....I can't remember the distance now. When listening in on Phoenix, I'd have my antenna pointing in that direction at a 45 deg angle towards phoenix. I usually observed in that same general direction....at least initially, but I'd often follow the sky upwards towards the zenith. There seemed to be no particular area in the sky, that I could say a visual would produce a radio signal in. Like I said previously, with the very bright meteors it didn't matter where in the sky it occurred, a radio signal was always heard. With the dimmer meteors it was hit or miss. With the statements of others...primarily Rainer Arlt, I summarized the following within my unpublished meteor observing guidebook. I once made copies to send these to others but I no longer do that. But you might want to refer to the following as I'm quoting myself":
"Radio signals reflected off a meteor's ionized and free electron column is done in two ways. These are known as Underdense and Overdense echoes.
UNDERDENSE - Underdense echoes are caused by a weakly ionizing meteor. Which means only a few electrons will be reflecting the radio waves. With this configuration of ionization, the radio beam will be reflected pretty much like that of a light with a flat mirror. The ionized column has to be aligned correctly to reflect a signal from a transmitter to a distant receiver.
OVERDENSE - Overdense echoes are caused by a strongly ionizing meteor. Which means that a high density of electrons are found in the meteor trail. This high electron density has the looks and behavior of a cylinder that reflects radio waves in all directions. Radio reflections can be detected even when the ionized column is not aligned like a mirror to reflect a signal. This allows the detection of overdense meteors in a larger area. Also the number of overdense echoes will increase much steeper during a major shower maximum than the underdense echo number. This is not only due to the lower population index, but mainly due to the easier alignment for "bright" echoes to be detected".
Good luck!
GeoZay