[Lf] [Fwd: LF: RE: RE: Fieldstrength at sunrise]

[Andre' Kesteloot]

"M. Sanders (PA3BSH)" wrote:

> Hello Marucus and group,
>
> Shaving mirrors and parabolic dishes do not have an apparent phasing problem
> because they reflect the E/H plane in an area relatively small compared to
> the phase velocity (speed of light). All reflected em waves remain almost in
> phase.
>
> Waves reflecting on moving mirrors show doppler effect, do we observe this
> at dawn/dusk on LF?
>
> If a mirror is 'made' 50-90 km in height (above the biosphere) and covering
> an area of tens of thousands of square kilometers then timing differences
> will occur between the hypothetical electromagnetic 'ray' taking the short
> route and the 'ray' taking the long route. Since all em waves travel in the
> same speed an interference pattern would be caused at the receiving end
> (like groundwave/skywave interferance). These patterns would be different
> for each wavelengt and signal strength differences would be noted at certain
> receiving distances. In practice no such significant differences have been
> recorded, therefore it can still be concluded there is not a single mirror
> in the sky.
>
> > I just don't quite follow your first paragraph:
> >
> > > A focusing-mirror would have a different effect on each
> > wavelength, since
> > > phasing phenomena are dependent on wavelength.
> >
> > If you look at the reflection in terms of plain geometrical optics, no
> > diffraction or coherent wave interference is needed. It works
> > like a shaving
> > mirror or a broadband parabolic dish.
>
> Greetings and best 73's
>
> Michael Sanders, PA3BSH.