Wouldn't that provide a better coverage with less fading compared to
traditional approach? Or is it that shortwave needs ionosphere to
work at all? Thanks.

"Jim" wrote in message
om...
Wouldn't that provide a better coverage with less fading compared to
traditional approach? Or is it that shortwave needs ionosphere to
work at all? Thanks.

Seems to me that the signal would have a pretty difficult time penetrating
the ionosphere at HF frequencies.There are of course complications to that
answer, such as MUF and incident angle, but in general if the ionosphere
acts to reflect earth originated signals, it will do the same to space
originated signals.

Dale W4OP

The ionosphere isn't anything like a perfect mirror.
RF at or below the MUF still penetrates, some fo it
refracts.
A friend just received her PHD in astrondomy and her
thesis was based on observations on the 2 HF
radio astronomy allocations.
Even with the MUF right above either of these 2 freqs,
signals stll penetrated the ionosphere.

I will ask Ms C how mcuh attenuation there was.
From conversations, it wasn't as much as I thought.
It seems that even at best, less then 10% of the RF
refracts in the ionosphere, the rest "punches" through.

Terry

In article .com,
wrote:

The ionosphere isn't anything like a perfect mirror. RF at or below
the MUF still penetrates, some fo it refracts. A friend just received
her PHD in astrondomy and her thesis was based on observations on the
2 HF radio astronomy allocations. Even with the MUF right above
either of these 2 freqs, signals stll penetrated the ionosphere.

I will ask Ms C how mcuh attenuation there was. From conversations,
it wasn't as much as I thought. It seems that even at best, less then
10% of the RF refracts in the ionosphere, the rest "punches" through.

The mechanics of how EM waves "bounce" off the ionosphere is a good
question for a PH.D. The current explanation of refraction seems
likely. If it is refraction then I would expect most of the energy to
be refracted and the rest lost in heating the ionosphere. When I have
used prisms with light waves in experiments most of the light energy was
bent to the same path (little scattering) depending on wavelength so if
the ionosphere is doing the same thing with radio waves then I would
expect the same with the difference of possibly higher loses in the
ionosphere itself.

I would expect all the radio wave energy to follow the same path until
there is significant heating of the ionosphere by the radio wave energy,
which at that point would be modifying the ionosphere medium.

The refraction concept has the EM waves incident to a boundary of
dielectric change. The wave path is bent according to the frequency of
the EM wave and the delta of the change in dielectric constants. Another
factor to consider is the angle of incidence so three factors are
involved that determine the outcome of where the energy goes but it
looks to me that most of the energy follows the same path so if 10% of
RF only gets refracted then I just don't understand what is going on
with radio waves and the ionosphere.

--
Telamon
Ventura, California

Jim wrote:
Wouldn't that provide a better coverage with less fading compared to
traditional approach? Or is it that shortwave needs ionosphere to
work at all? Thanks.

When you transmit a shortwave signal from an earth-bound transmitter, it
gets "bounced" off the ionosphere to come back down to the listener a
few thousand miles away.

If you were to transmit such a signal from space, it would bounce in
pretty much the same way -- except that instead of bouncing down to a
listener on Earth, it would bounce back out into space. Not
particularly useful.

--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

On Mon, 16 May 2005 02:01:18 +0000, Doug Smith W9WI wrote:

When you transmit a shortwave signal from an earth-bound transmitter, it
gets "bounced" off the ionosphere to come back down to the listener a
few thousand miles away.

If you were to transmit such a signal from space, it would bounce in
pretty much the same way -- except that instead of bouncing down to a
listener on Earth, it would bounce back out into space. Not
particularly useful.

Nonsense (at least above the MUF). Consider QSOs made using Mode K (21
MHz uplink, 29 MHz downlink) of the RS-10/11 and RS-12/13 ham satellites.

=====
RS-12 RADIO SPORT RS-12
Catalog number: 21089
Launched: February 5, 1991

Uplink: 21.210 to 21.250 MHz CW/USB Downlink: 29.410 to 29.450 MHz
CW/USB Beacon: 29.408 MHz
Robot: 29.454 MHz
[05232004]
=====

Snowbat wrote:

On Mon, 16 May 2005 02:01:18 +0000, Doug Smith W9WI wrote:

When you transmit a shortwave signal from an earth-bound transmitter, it
gets "bounced" off the ionosphere to come back down to the listener a
few thousand miles away.

If you were to transmit such a signal from space, it would bounce in
pretty much the same way -- except that instead of bouncing down to a
listener on Earth, it would bounce back out into space. Not
particularly useful.

Nonsense (at least above the MUF). Consider QSOs made using Mode K (21
MHz uplink, 29 MHz downlink) of the RS-10/11 and RS-12/13 ham satellites.

I recall listening to a satellite launched by China that played 'The East is
Red' as it came within range. Don't recall the frequency right off hand but
think it was up near 20 MHz or so. Perhaps someone else remembers it.

dxAce
Michigan
USA

dxAce wrote:

Snowbat wrote:

On Mon, 16 May 2005 02:01:18 +0000, Doug Smith W9WI wrote:

When you transmit a shortwave signal from an earth-bound transmitter, it
gets "bounced" off the ionosphere to come back down to the listener a
few thousand miles away.

If you were to transmit such a signal from space, it would bounce in
pretty much the same way -- except that instead of bouncing down to a
listener on Earth, it would bounce back out into space. Not
particularly useful.

Nonsense (at least above the MUF). Consider QSOs made using Mode K (21
MHz uplink, 29 MHz downlink) of the RS-10/11 and RS-12/13 ham satellites.

I recall listening to a satellite launched by China that played 'The East is
Red' as it came within range. Don't recall the frequency right off hand but
think it was up near 20 MHz or so. Perhaps someone else remembers it.

I did a quick Google and did find that that particular satellite was launched on
April 24, 1970 and used 20.009 Mhz to broadcast 'The East is Red'.

dxAce
Michigan
USA

On Mon, 16 May 2005 01:51:02 -0400, dxAce wrote:

I recall listening to a satellite launched by China that played 'The East is
Red' as it came within range. Don't recall the frequency right off hand but
think it was up near 20 MHz or so. Perhaps someone else remembers it.

CHINA-1 and CHINA-2 seem to fit your description:
http://www.svengrahn.pp.se/histind/China12/China12.htm

Snowbat wrote:

On Mon, 16 May 2005 01:51:02 -0400, dxAce wrote:

I recall listening to a satellite launched by China that played 'The East is
Red' as it came within range. Don't recall the frequency right off hand but
think it was up near 20 MHz or so. Perhaps someone else remembers it.

CHINA-1 and CHINA-2 seem to fit your description:
http://www.svengrahn.pp.se/histind/China12/China12.htm

I'll have to get a sound-card going again here as it would be a thrill to listen
to the recording they have up there on the site.

Almost as much of a thrill as it was to hear it live at the time I'll bet.

dxAce
Michigan
USA