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Re: (meteorobs) meteor detection in AM SW band

Hi:
You are correct about the complexity of electromagnetic propagation, 
and there are may many texts and papers written about the propagation 
of radio signatures and computer programs to determine MUF.

But I believe in the "keep it simple." If an individual is interested 
in experimenting, start with the simplist of tools and basic of 
readings.

Who was it that said.... "to enjoy meteors, all you need are your 
eyes ?"

George John Drobnock

--- In meteorobs@yahoogroups.com, Michael Linnolt <mlinnolt@a...> 
wrote:
> These statements regarding the transparency of our atmosphere to RF 
are a substantial oversimplification, and hence not really accurate. 
The transparency of our atmosphere (actually the ionospheric layer)
to 
vertically incident waves is given by the parameter fc (critical 
frequency). Frequencies above fc penetrate through to space, while 
those below are reflected back to earth. fc varies tremendously with 
time of day, geographical location, season, 27-day and 11-year solar 
cycle. It can be as high as 50-60Mhz (6 meters) during daytime
11-year 
solar maximum, and as low as 1 Mhz (300 meters) during night at solar 
minimum. In addition, the transparency is a function of angle of 
incidence, which along with fc, determines the MUF (maximum usable 
frequency) for HF radio transmissions. MUF more closely tracks the 
frequencies of interest for any meteor scatter work, since it deals 
with propagation at the typical low incidence angles for terrestrial 
signals. MUF varies from a high of around 70Mhz to a low around 
2-3Mhz.
> 
> The science of ionospheric radio wave propagation is complex, with 
sophisticated models and software available to track these parameters 
and frequencies, in near real time. Anyone interested in using these 
range of frequencies for meteor scatter should be aware of these 
issues, and not rely solely on oversimplified and generalized 
statements as presented here by CR Kitchen.
> 
> Mike Linnolt
> 
> --- drobnock2 <drobnock@p...> wrote:
> 
> >  See -- C. R. Kitchen, "Astrophysical Techniques,"
> > Adam Hilger, Ltd., 
> > 1984 revised 1991.
> > 
> > Kitchen  makes the statement that in radio astronomy
> > - scatter radio 
> > is within this astronomy  - the sky is transparent
> > for electromagnetic 
> > radio between 10mm and 10 meters (microwave to 25
> > mHz). He further 
> > states that electromagnetic radiation greater than
> > 50 meters 
> > (transmitted from earth) fails to penetrate the
> > atmosphere and is 
> > reflected back into the atmosphere.
> >
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