In rec.radio.amateur.antenna Jeff Liebermann wrote:
On Mon, 7 Dec 2015 01:17:34 -0000, wrote:

The term is "skywave" and it is not known to happen below 500 kHz.

I beg to differ. The current issue of QEX has an article on a WWVB 60
KHz frequency standard:
http://www.arrl.org/files/file/QEX_Next_Issue/2015/Nov-Dec_2015/Magliacane.pdf
On Pg 15 is the section on 60 KHz propagation:
LF radio propagation is substantially different from that
which exists at higher frequencies. Its remarkable stability
and reliability have often led to the belief that 60 kHz
signals propagate great distances over ground wave paths alone.
In reality, a combination of surface wave and D-layer
ionospheric paths are responsible for WWVB signal propagation.
At night, cosmic background radiation supports a level of
D-layer ionization that is sufficient for propagating LF (and
lower frequency) radio signals over long distances. Greater
D-layer efficiencies and increased effective height with
decreased ionization levels contribute to greater signal
coverage during the nighttime hours. etc...

Note that nowhere in there is the term skywave used.

So, here we have propagation via the ionospheric D-Layer which I
believe is considered a skywave. Note that the author talks about
measuring broadcast band frequencies to an accuracy 312 micro-hertz,
where such things as varying path lengths are important.

The wavelength of 60 KHz is about 5 km. The height of the D layer
varies from 60 to 90 km or about 12 to 18 wavelengths at 60 KHz.
That's too big for a waveguide structure, which suggests that the
dominant mode of propagation is skywave, not ground wave.

We will have to disagree here.

If it were reflections from the D-layer, one would expect to see a
"hole" in the signal level starting at around a few hundred miles or so
extending to around a thousand miles or so where the level would come
back up.

Such "holes" in signal strength from skywave propagation are easily
seen in the plots you can get from the pskreporter web site.

There are no holes in the WWVB signal strength.

Something else is at play here but I'm not sure what to call it, but
I would not call it skywave.

There is no frequency at which ground wave ceases and skywave takes
over. There seems to be quite a bit of overlap.

Yes, and it is again easily seen in the plots from pskreporter, expecially
on 160 and 80 meters.

Mo
https://en.wikipedia.org/wiki/Very_low_frequency#Propagation_characteristics

Here it is refered to as "ducting".

Sounds like a better term to me.



--
Jim Pennino

In message ,
writes



Define MF; there is no exact frequency where skywave ceases to exist, but
it has not been observed below 500 kHz. That does not mean that under
some extreme ionospheric conditions is can not happen, it means no one
has ever seen it happen.

Ummmmmmmmm.....

BBC Radio 4 on 198kHz is receivable (weakly) in Malta (900 miles?). It's
definitely stronger at night. Why is that?



--
Ian

On 07/12/2015 01:17, wrote:
In rec.radio.amateur.antenna Spike wrote:
On 06/12/2015 18:29, wrote:
In rec.radio.amateur.antenna Spike wrote:
On 06/12/2015 00:06, wrote:

snip

Your problem, or at least one of them, is that your first response
included this statement:

"Sky wave propagation doesn't happen at those frequencies for all practical
purposes."

I let this slide in the interests of discussion, but seeing as you wish
to nit-pick and be rude, we'll revisit this by my asking you what you
meant, as you are implying that there is in fact some form of skywave at
these low-MF Aeronautical beacon frequencies. Please explain.

I see you finally read the link so now you think you are going to sharp
shoot the original post.

BTW, "for all practical purposes" is synonymous with "unlikely to ever
happen".

You don't seem to know whether or not sky-wave exists at these
frequencies. 'Practically', sky-wave would be unreliable for NDB
working, but that doesn't mean to say sky-waves don't exist. When you
make up your mind about the topic, let me know what your answer is. To
help you, there is a shed-load of information out there on MF sky-wave
propagation.

The term is "skywave" and it is not known to happen below 500 kHz.

While doing that, please also explain what you think it is that causes
the claimed variations in the ground wave than enable DX beacon hunters
to hear such stations at very long ranges.

Search for "ground wave propagation" and read up on it.

I can't take that from someone who doesn't know that sky-wave exists at MF.

Once again, the term is "skywave".

Define MF; there is no exact frequency where skywave ceases to exist, but
it has not been observed below 500 kHz. That does not mean that under
some extreme ionospheric conditions is can not happen, it means no one
has ever seen it happen.

Your variable ground-wave is a hoot.

The term is "ground wave" and ALL propagation modes are variable due
to many reasons; a heavy rainstorm will effect ground wave propagation
as it changes the ground conductivity.

The relevant quotes are he

Sky wave propagation doesn't happen at those frequencies for all practical purposes.

Tell that to the beacon DX hunters.

That is ground wave propagation; I'd give you a link but you obviously
prefer to pull crap out of your ass to reading links.

You're a troll, aren't you?

Says someone that can not even use the correct terms.

Jeff Liebermann (to whom thanks are due) has just blown you out of the
water with some indications of how important the D layer is to
propagation of signals over a wide band of frequencies. HTH

TTFN


--
Spike

"Crime butchers innocence to secure a throne, and innocence struggles
with all its might against the attempts of crime"

- Maximilien Robespierre

"Ian Jackson" wrote in message
...
In message ,
writes
Define MF; there is no exact frequency where skywave ceases to exist, but
it has not been observed below 500 kHz. That does not mean that under
some extreme ionospheric conditions is can not happen, it means no one
has ever seen it happen.

Ummmmmmmmm.....

BBC Radio 4 on 198kHz is receivable (weakly) in Malta (900 miles?). It's
definitely stronger at night. Why is that?


'Cos they increase power at night?
--
;-)
..
73 de Frank Turner-Smith G3VKI - mine's a pint.
..
http://turner-smith.uk

In message , FranK Turner-Smith G3VKI
writes
"Ian Jackson" wrote in message
...
In message ,
writes
Define MF; there is no exact frequency where skywave ceases to exist, but
it has not been observed below 500 kHz. That does not mean that under
some extreme ionospheric conditions is can not happen, it means no one
has ever seen it happen.

Ummmmmmmmm.....

BBC Radio 4 on 198kHz is receivable (weakly) in Malta (900 miles?).
It's definitely stronger at night. Why is that?


'Cos they increase power at night?

They don't (certainly not that I'm aware).
--
Ian

"Ian Jackson" wrote in message
news
In message , FranK Turner-Smith G3VKI
writes
"Ian Jackson" wrote in message
...
In message ,
writes
Define MF; there is no exact frequency where skywave ceases to exist,
but
it has not been observed below 500 kHz. That does not mean that under
some extreme ionospheric conditions is can not happen, it means no one
has ever seen it happen.

Ummmmmmmmm.....

BBC Radio 4 on 198kHz is receivable (weakly) in Malta (900 miles?). It's
definitely stronger at night. Why is that?


'Cos they increase power at night?

They don't (certainly not that I'm aware).

Moonbounce?
--
;-)
..
73 de Frank Turner-Smith G3VKI - mine's a pint.
..
http://turner-smith.uk

On 07/12/2015 08:22, Ian Jackson wrote:

BBC Radio 4 on 198kHz is receivable (weakly) in Malta (900 miles?). It's
definitely stronger at night. Why is that?

It's jimp's newly-invented variable ground wave.


--
Spike

"Crime butchers innocence to secure a throne, and innocence struggles
with all its might against the attempts of crime"

- Maximilien Robespierre

On Mon, 7 Dec 2015 07:22:53 -0000, wrote:

In rec.radio.amateur.antenna Jeff Liebermann wrote:
On Mon, 7 Dec 2015 01:17:34 -0000, wrote:

The term is "skywave" and it is not known to happen below 500 kHz.

I beg to differ. The current issue of QEX has an article on a WWVB 60
KHz frequency standard:
http://www.arrl.org/files/file/QEX_Next_Issue/2015/Nov-Dec_2015/Magliacane.pdf
On Pg 15 is the section on 60 KHz propagation:
LF radio propagation is substantially different from that
which exists at higher frequencies. Its remarkable stability
and reliability have often led to the belief that 60 kHz
signals propagate great distances over ground wave paths alone.
In reality, a combination of surface wave and D-layer
ionospheric paths are responsible for WWVB signal propagation.
At night, cosmic background radiation supports a level of
D-layer ionization that is sufficient for propagating LF (and
lower frequency) radio signals over long distances. Greater
D-layer efficiencies and increased effective height with
decreased ionization levels contribute to greater signal
coverage during the nighttime hours. etc...

Note that nowhere in there is the term skywave used.

True. That would have been too easy.
https://en.wikipedia.org/wiki/Skywave
In radio communication, skywave or skip refers to the
propagation of radio waves reflected or refracted back
toward Earth from the ionosphere, an electrically charged
layer of the upper atmosphere.
In other words, anything that bounces at least once off the ionosphere
or earth is a skywave. The D-layer mechanism is described is most
cerainly a skywave.

So, here we have propagation via the ionospheric D-Layer which I
believe is considered a skywave. Note that the author talks about
measuring broadcast band frequencies to an accuracy 312 micro-hertz,
where such things as varying path lengths are important.

The wavelength of 60 KHz is about 5 km. The height of the D layer
varies from 60 to 90 km or about 12 to 18 wavelengths at 60 KHz.
That's too big for a waveguide structure, which suggests that the
dominant mode of propagation is skywave, not ground wave.

We will have to disagree here.

That's why I posted my rant. The idea that VLF signal will reflect or
refract off the D-layer is new to me. I had always assume that
everything with a wavelength longer than the BCB is ground wave.
Apparently not.

If it were reflections from the D-layer, one would expect to see a
"hole" in the signal level starting at around a few hundred miles or so
extending to around a thousand miles or so where the level would come
back up.

Such "holes" in signal strength from skywave propagation are easily
seen in the plots you can get from the pskreporter web site.

There are no holes in the WWVB signal strength.

The wavelength of WWVB is 5,000 meters and the D-layer is 12-18
wavelengths high. If I draw a scaled model of the earth, D-layer, and
the width of such a signal, there would be considerable overlap of the
incident and reflected signals, causing significant smearing of any
holes in the signal levels. You see those holes at 80m and up because
these shorter wavelengths don't have much overlap. That's not the
case at VLF, where longer wavelengths produce less distinct holes.
Anyway, if there really were holes in the WWVB coverage pattern, it
would have been noted in the propagation predictions and by numerous
users complaining of a loss of signal in specific areas.

Also, if propagation at 60 KHz were a mixture of sky and ground waves,
then the ground wave would also smear any gaps and holes. There might
be some change in signal levels near the alleged holes, but I don't
think you'll see anything under all the constantly changing
atmospheric noise.

Something else is at play here but I'm not sure what to call it, but
I would not call it skywave.

Good point. Nothing new can be discussed without first assigning a
name. Liebermann-wave does sound rather catchy. D-layer-ground-wave
is ugly. Duct-wave might work. Incidentally, it's likely that the
ground reflects, while the D-layer refracts at 60 KHz, adding
additional confusion.

https://en.wikipedia.org/wiki/Very_low_frequency#Propagation_characteristics
Here it is refered to as "ducting".
Sounds like a better term to me.

Ducting or Duct-wave are probably sufficiently vague. I had always
assumed that ducting operates exactly the same as in a waveguide (two
parallel quarter wave stubs elongated into a tube) with no internal
reflections involved. In this situation, it seems like anything that
can propagate between two conductive layers, either bouncing or
directly, can apply. Yeah, I guess that's vague enough.



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

In rec.radio.amateur.antenna Jeff Liebermann wrote:
On Mon, 7 Dec 2015 07:22:53 -0000, wrote:

In rec.radio.amateur.antenna Jeff Liebermann wrote:
On Mon, 7 Dec 2015 01:17:34 -0000, wrote:

The term is "skywave" and it is not known to happen below 500 kHz.

I beg to differ. The current issue of QEX has an article on a WWVB 60
KHz frequency standard:
http://www.arrl.org/files/file/QEX_Next_Issue/2015/Nov-Dec_2015/Magliacane.pdf
On Pg 15 is the section on 60 KHz propagation:
LF radio propagation is substantially different from that
which exists at higher frequencies. Its remarkable stability
and reliability have often led to the belief that 60 kHz
signals propagate great distances over ground wave paths alone.
In reality, a combination of surface wave and D-layer
ionospheric paths are responsible for WWVB signal propagation.
At night, cosmic background radiation supports a level of
D-layer ionization that is sufficient for propagating LF (and
lower frequency) radio signals over long distances. Greater
D-layer efficiencies and increased effective height with
decreased ionization levels contribute to greater signal
coverage during the nighttime hours. etc...

Note that nowhere in there is the term skywave used.

True. That would have been too easy.
https://en.wikipedia.org/wiki/Skywave
In radio communication, skywave or skip refers to the
propagation of radio waves reflected or refracted back
toward Earth from the ionosphere, an electrically charged
layer of the upper atmosphere.
In other words, anything that bounces at least once off the ionosphere
or earth is a skywave. The D-layer mechanism is described is most
cerainly a skywave.

I would disagree with that.

So, here we have propagation via the ionospheric D-Layer which I
believe is considered a skywave. Note that the author talks about
measuring broadcast band frequencies to an accuracy 312 micro-hertz,
where such things as varying path lengths are important.

The wavelength of 60 KHz is about 5 km. The height of the D layer
varies from 60 to 90 km or about 12 to 18 wavelengths at 60 KHz.
That's too big for a waveguide structure, which suggests that the
dominant mode of propagation is skywave, not ground wave.

We will have to disagree here.

That's why I posted my rant. The idea that VLF signal will reflect or
refract off the D-layer is new to me. I had always assume that
everything with a wavelength longer than the BCB is ground wave.
Apparently not.

Well, there is line of sight, but irrelevant here.

If it were reflections from the D-layer, one would expect to see a
"hole" in the signal level starting at around a few hundred miles or so
extending to around a thousand miles or so where the level would come
back up.

Such "holes" in signal strength from skywave propagation are easily
seen in the plots you can get from the pskreporter web site.

There are no holes in the WWVB signal strength.

The wavelength of WWVB is 5,000 meters and the D-layer is 12-18
wavelengths high. If I draw a scaled model of the earth, D-layer, and
the width of such a signal, there would be considerable overlap of the
incident and reflected signals, causing significant smearing of any
holes in the signal levels. You see those holes at 80m and up because
these shorter wavelengths don't have much overlap. That's not the
case at VLF, where longer wavelengths produce less distinct holes.
Anyway, if there really were holes in the WWVB coverage pattern, it
would have been noted in the propagation predictions and by numerous
users complaining of a loss of signal in specific areas.

The wavelength doesn't have any effect on where the reflections would
appear.

Redraw your scaled model using rays.

The holes appear from two mechanisms:

The first hole will appear between the farthest reaches of ground wave
and the nearest a reflected wave can hit the Earth.

Subsequent holes appear between the regions where reflection can hit
the Earth.

I've been watching propagation using pskreporter for a few years
now. Right now propagation is so poor all you see is the first hole
in the skip propagation with a little propagation into the second
"skip" region. About a year ago when the bands were in really good shape,
you could see the hole between the second and third "skip" region.

Also, if propagation at 60 KHz were a mixture of sky and ground waves,
then the ground wave would also smear any gaps and holes. There might
be some change in signal levels near the alleged holes, but I don't
think you'll see anything under all the constantly changing
atmospheric noise.

Ground wave only goes so far. Yes the distance varies with conditions,
but ground wave has no holes in coverage. Skywave doesn't normally
exist until well after ground wave has petered out.

Something else is at play here but I'm not sure what to call it, but
I would not call it skywave.

Good point. Nothing new can be discussed without first assigning a
name. Liebermann-wave does sound rather catchy. D-layer-ground-wave
is ugly. Duct-wave might work. Incidentally, it's likely that the
ground reflects, while the D-layer refracts at 60 KHz, adding
additional confusion.

https://en.wikipedia.org/wiki/Very_low_frequency#Propagation_characteristics
Here it is refered to as "ducting".
Sounds like a better term to me.

Ducting or Duct-wave are probably sufficiently vague. I had always
assumed that ducting operates exactly the same as in a waveguide (two
parallel quarter wave stubs elongated into a tube) with no internal
reflections involved. In this situation, it seems like anything that
can propagate between two conductive layers, either bouncing or
directly, can apply. Yeah, I guess that's vague enough.

A waveguide would have very little loss, while ducting would have a
lot of loss.


--
Jim Pennino

In rec.radio.amateur.antenna Spike wrote:
On 07/12/2015 08:22, Ian Jackson wrote:

BBC Radio 4 on 198kHz is receivable (weakly) in Malta (900 miles?). It's
definitely stronger at night. Why is that?

It's jimp's newly-invented variable ground wave.

All propagation modes are variable over time due to a number of reasons.

--
Jim Pennino