Hi All,

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Does this account for the peak and fade sinewave effect we get on
CFH over about an hour, both at US sunset and UK dawn?

Mike, G3XDV (IO91VT)

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Reference measurements around the time of the '99 eclipse have indeed shown
the same effect on 75kHz during sunrise and sunset. Since there should be a
multi hop sky wave propagation between Canada and the UK also multiple peak
and fade effects can occur.

However the observations can be explained by this effect only if the timing
of the events corellates with the dusk/dawn times at the position of the
reflections against the D-layer. Or puting it the other way around if we
study the timing of the effects we can approximate the location of the
reflections against the D-layer and find out what the number of hops is on
any lf DX propagational path. With some experience it should be possible to
predict signal sunset/dawn related signal peaks and make a DX-sked
accordingly.

BTW: A North-South path or v.v. does not show multiple effects since the
solar radiation changes at more or less the same time over the total
propagational path. The effect could be more intense in this case.
Propagational paths near the 'grey-line' should have a less intense effect,
possibly obscuring one or more hops along the great-circle path passing near
Iceland/Greenland.

Greetings,

Michael Sanders, PA3BSH