[Lf] more of propagation

[Andre' Kesteloot]

Väinö Lehtoranta wrote:

> David,
>
> Yes, skywaves or actually ionospheric waves!
> After being few years in CCIR SG6 IWP6/1 group
> I learned that original 'skywave' was a kind of
> ionospherically reflected (refracted), calibrated
> (by IWP6/1) species archived to CCIR databank.
> After that I began to talk and write about
> 'ionospheric wave', so all the others know that
> it was a component that came back to ground level
> after making a round trip to ionospheric region.
> No layman knows what is a 'skywave' as he/she
> thinks sky is something else than ionosphere.
> Some people mix it with 'space wave' which in
> fact is a combination of direct and reflected
> components, usually only above certain freqs.
> My English is not good enough to explain...
>
> Deep angle 'ionospheric' propagation with real
> 'ground bounces' is OK if you talk about NVIS
> (Near Vertical Incidence Skywave' propagation.
> If you talk about long distance propagation,
> as most hams are interested in and talking,
> this propagating wave with billions of 'rays'
> tries to avoid ground as far as possible.
>
> Deep incidence angle ray pictures have been
> produced for decades only because it is very
> difficul to draw the whole system to a nearly
> correct scale. So, most people are thinking of
> a 'skywave' as bouncing between the earth and
> one or more of the ionospheric layers while
> each of the billion rays tries to avoid the
> ground as far as possible - this is due to an
> extra attenuation caused by a 'ground bounce'.
>
> That is the main reason why 'skywave' forecasts
> are not usable for certain paths like the EU-
> Australia or EU-South Africa paths. Most of the
> predictions are still based on 'hops' instead
> of ionospherically ducted propagation modes.
>
> Some of the real researchers have estimated
> that 3/4 of so called 'transatlantic propagation'
> must be due to some type of ionospheric ducting,
> one question is: how often F2 is involved in it.
> Has anyone ever confirmed the existence of F1?
>
> Regards, Vaino, OH2LX
>
> At 18:21 17.8.2000 -0400, you wrote:
> >Hi Vaino    What did you mean  By "ground  bounces" ? Did you mean
> >skywaves?
> >
> >Väinö Lehtoranta wrote:
> >
> >> The behavior of propagation conditions on low
> >> frequency bands is a function of qth, latitude,
> >> etc. In our case almost any amount of extra hard
> >> x-ray precipitation to the D-region, which is what
> >> happens during certain flares, ruins low frequency
> >> conditions here. Our main MF test stations have been
> >> Norwegian Kvitsoy 1314 kHz and Kemi NDB 373 kHz.
> >> They both without exception get weaker or even
> >> disappear during even slight solar disturbance.
> >> We recorded Kvitsoy and other LF/MF frequencies for
> >> decades. SID effects are short lived but eg after
> >> the middle of this July Kvitsoy was inaudible here
> >> for several days. According to studies the mode
> >> on 1314 should be F2 only on short distances, so
> >> it is sometimes difficult to decide whether the
> >> F2 or E or both were affected by D-region block.
> >> 50 MHz people like to talk about transatlantic Es
> >> between say UK and NE America but it appears
> >> that F2 most certainly must play some part in it.
> >> There appears to be some kind of rather regular
> >> 'ionospheric ducting' on transatlantic paths.
> >> Most talk about 'ground bounces' is misleading.
> >>
> >> Regards, Vaino, OH2LX
> >> IARU Region 1 Auroral studies coordinator
> >>
> >> At 18:38 16.8.2000 -0000, you wrote:
> >> >have been watching the postings on CFH and DCF...
> >> >
> >> >just what is it you guys are monitoring for, and how are you doing it?
> >> >
> >> >what programs do I need etc.? or how may I participate?
> >> >
> >> >david
>
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