(meteorobs) Observability function O.F - newbie question
Frans Lowiessen
lowiess at planet.nl
Thu May 12 15:26:38 EDT 2005
mark ford wrote:
>Hi
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>I have a couple of questions about radio 'observability function' (O.F)
>but first some explanation of what I mean.
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>This is the effect that is seen when you listen/receive meteor pings via
>radio. As the radiant drifts across the sky, the angle between it (the
>radiant) and the radio transmitter changes. This means that because the
>meteors are coming from a gradually varying mean angle (relative to the
>observer) as the radiant position changes, the average apparent cross
>section of the meteor trail becomes smaller or larger. The net result
>is that the strength of the ping for a fixed meteor size varies with
>radiant position , so you get to a situation where you miss smaller
>pings because they are too faint and get extra strong pings as the
>radiant/meteor/transmitter angle 'improves'. This seems to makes radio
>detection unreliable especially for even slightly estimating magnitudes.
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>Now what people seem to do is work out an O.F correction graph, which
>allows for the radiant drift and apply this to the counts.
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>My questions are
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>a) How does one work this O.F correction curve out?
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I am no an expert on this but things to consider are gain patterns of
antenne an sensivty of the reveiver
>b) Could I vary the amplifier gain on the radio receiver inline
>with the O.F. (for example using PC software to control the gain with an
>electronic attenuator on a continuous basis), to fool the receiver into
>seeing a constant uniform 'signal strength' for a given radiant(s)?
>rather than post processing the information. (It actually would only
>need to be a PC audio volume control that varies with the O.F)
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Would be a nice idea but one can not amplify signal which is not present
you could reduce atteniate siganal
but is not very interesting i think
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>This assumes that 'worst case' is when a meteor trail is 'end on' to the
>receiver. Presumably you would still get a signal but it would be much
>reduced in intensity?
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The are other people who have doen some very good research in this area
and one of them Mr Belkovic will be attending the upcoming IMO-cogres in
Belgium
Greetings Frans Lowiessen (PE0F)
> (and obviously sporadic's will always have random directions so the
>true numbers /sizes will not be counted).
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>Any help appreciated!
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>Mark Ford
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