On Sat, 01 Jul 2006 18:32:46 -0400, jawod wrote:
This I don't understand. To me, refraction versus reflection IS the
issue. In optics, Brewster's angle is used. I still don't quite
understand thte PseudoBrewster's Angle...it seems to have a different
definition (at least in the ARRL book).

Hi John,

Perhaps you should offer that definition as its application seems to
be quite rare, and paired with some obscurity to the world of
sub-atomic dispersion.

I guess I was trying to get at how much ham radio is propagated into
space. Certainly SOME does.

SOME about covers it (you want that specified in dB?). I suppose by
your other references to SETI you are wondering about the chances of a
QSO in the same frequency from the other side of that ionospheric
curtain.

Given the odds, one frequency is as good as the next....

How does this compare to that amount propagated into space by Broadcast?

There you have to consider the magnitude of flux, continuously, over
the years. If the broadcasting is from Fox news (or any Murdoch
source for that matter), it will be indistinguishable from pinko
noise.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Sat, 01 Jul 2006 18:32:46 -0400, jawod wrote:

This I don't understand. To me, refraction versus reflection IS the
issue. In optics, Brewster's angle is used. I still don't quite
understand thte PseudoBrewster's Angle...it seems to have a different
definition (at least in the ARRL book).


Hi John,

Perhaps you should offer that definition as its application seems to
be quite rare, and paired with some obscurity to the world of
sub-atomic dispersion.

I looked in some of my dusty old Optics texts to find Brewster: has
more to do with polarization. Brewster's angle is the incident angle of
light at which the reflected beam is the most completely polarized.

My bad.

I was thinking of the critical angle above which the light is reflected
back from the media interface and below which the light is refracted
through the "2nd" medium.

PseudoBrewster's Angle (PBA) is the "angle at which the reflected wave
is 90 degrees out of phase with respect to the direct wave" (p. 3-13
ARRL Antenna Book).

I see now that Both Brewster and PBA have to do with polarization.


I guess I was trying to get at how much ham radio is propagated into
space. Certainly SOME does.


SOME about covers it (you want that specified in dB?). I suppose by
your other references to SETI you are wondering about the chances of a
QSO in the same frequency from the other side of that ionospheric
curtain.

Not really looking for a QSO. Just trying to imagine SWL from a
different vantage point, I guess.

Given the odds, one frequency is as good as the next....


How does this compare to that amount propagated into space by Broadcast?


There you have to consider the magnitude of flux, continuously, over
the years. If the broadcasting is from Fox news (or any Murdoch
source for that matter), it will be indistinguishable from pinko
noise.

Short entries in some entity's log: "No intelligent life found" and "why
am I suddenly hungry?".

73's
Richard Clark, KB7QHC

On Thu, 06 Jul 2006 22:42:57 -0400, jawod wrote:
PseudoBrewster's Angle (PBA) is the "angle at which the reflected wave
is 90 degrees out of phase with respect to the direct wave" (p. 3-13
ARRL Antenna Book).

Hi John,

That sounds like ****-poor definition.

I see now that Both Brewster and PBA have to do with polarization.

And certainly one has very little to do with the other - except for
polarization. I'm surprised the author of that article didn't append
his own name to the angle.

Not really looking for a QSO. Just trying to imagine SWL from a
different vantage point, I guess.

Somewhere near the 15 meter band you can get the noise field from
Jupiter. Not exactly sentient, but still an exotic contact.

73's
Richard Clark, KB7QHC

"jawod" wrote in message
...
Tried to make the subject grab a bit.

I just fininshed the ARRL Antenna Book Chapter on Effects of Ground. There
are HFTA graphs showing elevation response for various antenna
configurations (mostly Yagis).

Most arrays show good response up to 12 degrees above the horizon, then
many show a null and then, a second peak around 25 to 30 degrees above the
horizon.

that is a function of height. the main lobe from the antenna is aimed at
the horizon and there are other lobes from the design of then antenna. then
reflections from the ground cause more vertical variations. these are
dependent on the height and the terrain around the antenna.


Here's my question:
At 25 to 30 degrees elevation response, aren't these waves leaving the
ionosphere (i.e., refracted instead of reflected)?

not necessarily. look at the arrival angle statistics and you will see that
frequently very high angle propagation is possible. usually higher angles
mean shorter distances but at times you can get many short high angle hops
to cover long distances also.


Am I right to consider this component of propagation to have left the
earth?

This would indicate a substantial fraction of each amateur transmission
is sent into space.

I always thought Broadcast transmissions were most likely to emanate from
Earth. Are hams more or less likely to transmit into space than
Broadcast?

broadcast is more likely. there are many more broadcast stations on the air
24x7, over the same range of spectrum that we use, and running much higher
power than we use. the most likely signals to reach out from earth are
likely fm broadcast and tv signals since those are normally well above the
critical frequency that reflects from the ionosphere and can be fairly high
power. lower hf, mf, and lf are less likely to get out as they reflect from
the ionosphere even at very high angles.



John
(who wishes to remain a student and never an expert)

Dave wrote:


broadcast is more likely. there are many more broadcast stations on the air
24x7, over the same range of spectrum that we use, and running much higher
power than we use. the most likely signals to reach out from earth are
likely fm broadcast and tv signals since those are normally well above the
critical frequency that reflects from the ionosphere and can be fairly high
power. lower hf, mf, and lf are less likely to get out as they reflect from
the ionosphere even at very high angles.


Radar is the best we do, but not much information is transmitted beyond
the fact that we are here, the beam is usually narrow, and the direction
varies quickly. EME is a distant 2nd, carries real information in
simple codes, the direction varies slowly, the beamwidth is usually low
(on high GHz bands it can be less than the width of the moon), and the
number of transmitters is very low.

Either one of the previous could be picked up from a fair distance, but
not likely because of the narrow angles and varying direction. And
commercial broadcasting doesn't have the ERP in any particular direction
to carry far. We live next to a very large noise source that would tend
to swamp out what we generate.

tom
K0TAR

Tom Ring wrote:

Radar is the best we do, but not much information is transmitted beyond
the fact that we are here, the beam is usually narrow, and the direction
varies quickly. EME is a distant 2nd, carries real information in
simple codes, the direction varies slowly, the beamwidth is usually low
(on high GHz bands it can be less than the width of the moon), and the
number of transmitters is very low.

Either one of the previous could be picked up from a fair distance, but
not likely because of the narrow angles and varying direction. And
commercial broadcasting doesn't have the ERP in any particular direction
to carry far. We live next to a very large noise source that would tend
to swamp out what we generate.

VHF and UHF emissions escalated rapidly after WWII with the
popularization of TV, and these readily penetrate the ionosphere. So
there's a sphere of such emissions radiating outward from the Earth at
the speed of light. And at the leading edge of this radiation sphere are
the McCarthy hearings and the Howdy Doody show. No wonder the ETs have
left us alone!

Roy Lewallen, W7EL

Roy Lewallen wrote:

VHF and UHF emissions escalated rapidly after WWII with the
popularization of TV, and these readily penetrate the ionosphere. So
there's a sphere of such emissions radiating outward from the Earth at
the speed of light. And at the leading edge of this radiation sphere are
the McCarthy hearings and the Howdy Doody show. No wonder the ETs have
left us alone!

Roy Lewallen, W7EL

What was wrong with Howdy Doody?

tom
K0TAR

Dave wrote:
"jawod" wrote in message
...

Tried to make the subject grab a bit.

I just fininshed the ARRL Antenna Book Chapter on Effects of Ground. There
are HFTA graphs showing elevation response for various antenna
configurations (mostly Yagis).

Most arrays show good response up to 12 degrees above the horizon, then
many show a null and then, a second peak around 25 to 30 degrees above the
horizon.


that is a function of height. the main lobe from the antenna is aimed at
the horizon and there are other lobes from the design of then antenna. then
reflections from the ground cause more vertical variations. these are
dependent on the height and the terrain around the antenna.


Here's my question:
At 25 to 30 degrees elevation response, aren't these waves leaving the
ionosphere (i.e., refracted instead of reflected)?


not necessarily. look at the arrival angle statistics and you will see that
frequently very high angle propagation is possible. usually higher angles
mean shorter distances but at times you can get many short high angle hops
to cover long distances also.


Am I right to consider this component of propagation to have left the
earth?

This would indicate a substantial fraction of each amateur transmission
is sent into space.

I always thought Broadcast transmissions were most likely to emanate from
Earth. Are hams more or less likely to transmit into space than
Broadcast?


broadcast is more likely. there are many more broadcast stations on the air
24x7, over the same range of spectrum that we use, and running much higher
power than we use. the most likely signals to reach out from earth are
likely fm broadcast and tv signals since those are normally well above the
critical frequency that reflects from the ionosphere and can be fairly high
power. lower hf, mf, and lf are less likely to get out as they reflect from
the ionosphere even at very high angles.



John
(who wishes to remain a student and never an expert)



Thanks to all for the "enlightenment".

Guess I've got a little SETI streak in me. I just got back a copy of an
Astrobiology text that I borrowed out. It's by Gilmour and Sephton,
Cambridge University Press if anyone's interested.

John

Dear John:
If you were a radio amateur who is interested in working other radio
amateurs at a great distance, then you wish to have a significant portion of
your antenna's radiation within about 12 to 2 degrees above the horizon.

In tern, this goal suggests that a preferred height for an HF,
horizontally-polarized antenna is between 2 and 2.5 wavelengths above
ground.

If the higher angle radiation does not pass through the ionosphere, it
contributes to interference to (relatively) nearby stations (and, because
the antenna probably is used for reception, contributes to hearing nearby
stations). Expensive HF antenna systems exist that significantly suppress
all except the lowest lobe.

If you wish to be a student of antennas, do invest in Kraus' 3rd edition
of Antennas. Read and study the book starting with the first chapter.

Regards, Mac N8TT


--
J. Mc Laughlin; Michigan U.S.A.
Home:
"jawod" wrote in message
...
Tried to make the subject grab a bit.

I just fininshed the ARRL Antenna Book Chapter on Effects of Ground.
There are HFTA graphs showing elevation response for various antenna
configurations (mostly Yagis).

Most arrays show good response up to 12 degrees above the horizon, then
many show a null and then, a second peak around 25 to 30 degrees above
the horizon.

Here's my question:
At 25 to 30 degrees elevation response, aren't these waves leaving the
ionosphere (i.e., refracted instead of reflected)?

Am I right to consider this component of propagation to have left the
earth?

This would indicate a substantial fraction of each amateur transmission
is sent into space.

I always thought Broadcast transmissions were most likely to emanate
from Earth. Are hams more or less likely to transmit into space than
Broadcast?

John
(who wishes to remain a student and never an expert)

On Sat, 01 Jul 2006 11:09:22 -0400, jawod wrote:

Tried to make the subject grab a bit.

I just fininshed the ARRL Antenna Book Chapter on Effects of Ground.
There are HFTA graphs showing elevation response for various antenna
configurations (mostly Yagis).

Most arrays show good response up to 12 degrees above the horizon, then
many show a null and then, a second peak around 25 to 30 degrees above
the horizon.

Here's my question:
At 25 to 30 degrees elevation response, aren't these waves leaving the
ionosphere (i.e., refracted instead of reflected)?

Am I right to consider this component of propagation to have left the earth?

This would indicate a substantial fraction of each amateur transmission
is sent into space.

I always thought Broadcast transmissions were most likely to emanate
from Earth. Are hams more or less likely to transmit into space than
Broadcast?

John
(who wishes to remain a student and never an expert)


To: "Richard Clark"
Subject: Please Post in rraa
From: "Walter Maxwell"
Date: Sat, 1 Jul 2006 17:31:29 -0400

Richard, I've been trying to post the msg below to the HFTA-ARRL-Space
thread, but after three attempts to send it it doesn't get posted.
Would you please post it for me in the spot following Mac's?

Walt, W2DU

Hello John,

I believe your other respondents missed one of your points concerning
reflection and refraction, and therefore didn't respond completely to
it.

Whether reflection, refraction, or total penetration of the ionosphere
occurs depends on the ionospheric layer, the time of day that
determines the sun angle on the layer, the resulting level of
ionization, the angle the ray makes on incidence with the layer, and
the frequency of the energy in the arriving ray.

Consequently, the answer is complex. As we know, when the frequency is
high enough (VHF and above) the result is total penetration--no
reflection or refraction--line of sight reception only.

On the other hand, at HF the ratio between reflection and refraction
varies. There are times when both occur. During those times the
portion of the incident ray that is reflected returns to earth, while
the portion that is refracted continues on through the ionosphere into
space and never returns. I'm not sufficiently knowledgeable on the
subject to go into further detail, but now that they've been nudged,
either Richard C or Reggie can. Or someone else more knowledgeable
than I.

Walt, W2DU