[Uram-rejections] Skywave propagation at low frequencies

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> From webstump at chiark.greenend.org.uk Sat Dec 19 18:53:31 2015
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> From: "Jimbo ..." <james.stewart497 at ntlworld.com>
> Newsgroups: uk.radio.amateur.moderated
> Subject: Re: Skywave propagation at low frequencies
> Date: Sat, 19 Dec 2015 18:53:24 -0000
> Organization: A noiseless patient Spider
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> 
> "Brian Reay" <no.sp at m.com> wrote in message 
> news:n545ai$9j6$1 at dont-email.me...
> > On 19/12/2015 16:43, Richard Lamont wrote:
> >> On 19/12/15 16:14, Brian Reay wrote:
> >>> Richard Lamont <richard at lamont.me.uk> wrote:
> >>>> On 15/12/15 23:11, Ian Jackson wrote:
> >>>>
> >>>>> If the D-layer also absorbs the even lower frequencies (for instance,
> >>>>> the LW broadcast signals), and if there actually IS propagation via
> >>>>> ducting, I would have thought that the lossy D-layer would attenuate 
> >>>>> the
> >>>>> RF signal as it 'rubs along' the upper side of the duct. At night, 
> >>>>> when
> >>>>> D-layer disappears, the duct would widen, and upper side would then be
> >>>>> the more-reflective, less-lossy F1 and F2 layers - thus allowing the
> >>>>> radio wave to propagate to greater distances.
> >>>>
> >>>> AIUI the E layer critical frequency at night is usually somewhere in 
> >>>> the
> >>>> MF broadcast band, so any refraction of LF is done by the E-layer 
> >>>> before
> >>>> it gets to the F layer.
> >>>
> >>> What electron density are you assuming? I've just done a quick 
> >>> calculation
> >>> and that would only be true for a low angle of attack as f critical is
> >>> lower than you suggest.
> >>
> >> I wasn't assuming anything about electron density. My knowledge of
> >> propagation is pretty limited, and my comment came from half-remembering
> >> some broadcast engineering tome I read donkeys' years ago.
> >>
> >> This may be of interest:
> >> https://www.itu.int/rec/R-REC-P.684-6-201202-I/en
> >>
> >
> > OK.
> >
> > I was just curious, being a mathematician I tend to check things against 
> > the numbers and they don't seem to quite stack up. However, there may be 
> > another factor involved so I've no wish to make a thing of it.
> >
> > I've always thought the F layer was the key player after sunset but, if 
> > you look at the altitudes, things get a bit less clear cut- especially if 
> > the E layer plays more of a part.
> >
> >
> > Out of interest, I recall being told that the E layer was the first to be 
> > identified and was referred to the Heaviside layer for sometime. A gem my 
> > Grammar school Geography teacher came out with, he seemed to know quite a 
> > bit about the Ionosphere.
> >
> >
> >
> >
> He was probably a class A radio Amateur ... 
> 
> 
> 
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