Text 29502, 46 rader
Skriven 2012-06-05 14:21:06 av Richard Webb (1:116/901.0)
  Kommentar till text 29499 av Michiel van der Vlist (2:280/5555)
Ärende: Fidonews Vol 29 No 23 June 04, 2012 Page: 2
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hello Michiel,

On Tue 2012-Jun-05 09:33, Michiel van der Vlist (2:280/5555) wrote to Ward
Dossche:

 WD> That fact that the Ithasca heard Earhart at 3105kHZ is an indication
 WD> she was real close because Earhart's transmitter flying at 1,000ft
 WD> only could reach about 50 miles.

MvdV> For the so called ground wave.

YEs, agreed.

MvdV> There is however ionospheric reflection. During daylight
MvdV> frequencies in that range are reflected by the the E-layer, also
MvdV> called the Kennely-Hevyside layer. The hight of the E-layer is 100
MvdV> - 130 km. So single hop signals can easily reach hundreds of
MvdV> kilometers.

Indeed, nighttimes especially, but I"ve seen daytime props
on nearby frequencies that would cover that distance.

 WD>  As a reference Nikumaroro is 400 miles away, she never could've been
 WD> there.

MvdV> I'd say 400 miles - although maybe too far for a relyable 24/7
MvdV> connection - is very well possible on that frequency. Short wave
MvdV> propagation is fickle and depends on many circumstances that vary
MvdV> in a hard to predict way. That frequency is close to the 80 meter
MvdV> ham band and radio amateurs often cover such distances. 


Indeed, and that part of the spectrum would be one of my
go-to frequencies, anywhere from late afternoon through the
night, and maybe in the daytime.  IF that weren't choice #1
for a frequency, band wise it would at least be #2.
That's why 80 and 40 meters, i.e. 3.5 and 7 mhz are the
go-to places for regional emergency work.  That 3 mhz
channel would have been especially reliable during a solar
minimum imho.


Regards,
           Richard
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 * Origin:  (1:116/901)