"Richard Clark" wrote in message
...
On Tue, 6 Feb 2007 22:35:04 -0500, "Stefan Wolfe"
wrote:

2. The effect of the 80m hill 10Km away is negligible. The arc tan is only
.008 degrees, thus the transmitter hardly "sees" it.

Actually, Stefan, the transmitter cannot see through it at all.

Exactly . And taking into account the 15 degree bend of the radio horizon
(even at 10 GHz) vs the arctan of .008 degrees for the the hill, reduced
somewhat by the 20 foot transmitter tower to .006 degrees, the hill itself
is invisible at a 30km far field. The bend of the propagating waves which
extends the radio horizon clearly mitigates any possible effects of the 80m
hill.

On Wed, 7 Feb 2007 00:08:19 -0500, "Stefan Wolfe"
wrote:


"Richard Clark" wrote in message
.. .
On Tue, 6 Feb 2007 22:35:04 -0500, "Stefan Wolfe"
wrote:

2. The effect of the 80m hill 10Km away is negligible. The arc tan is only
.008 degrees, thus the transmitter hardly "sees" it.

Actually, Stefan, the transmitter cannot see through it at all.

Exactly . And taking into account the 15 degree bend of the radio horizon
(even at 10 GHz) vs the arctan of .008 degrees for the the hill, reduced
somewhat by the 20 foot transmitter tower to .006 degrees, the hill itself
is invisible at a 30km far field. The bend of the propagating waves which
extends the radio horizon clearly mitigates any possible effects of the 80m
hill.


Hi Stefan,

You seem to be simultaneously agreeing and disagreeing. The hill is
either in the way, or it is not. It is in the way. To count on an
intermediary, such as suggested by Jimmie, knife-edge propagation or
bend of the waves, is probably not in our student's syllabus. Besides,
I have seen neither you nor Jimmie offer the attenuation presented by
such refractions (and the attenuation is not marginal). Without
quantifiables, the path budget cannot be calculated.

The problem, as stated, has a clear answer in looking over the hill by
raising one antenna, the question informs us that is the answer and
that is simply resolved with trig (albeit, including the radius of
earth and accounting for its curvature).

73's
Richard Clark, KB7QHC

Richard Clark wrote:

Hi Stefan,

You seem to be simultaneously agreeing and disagreeing. The hill is
either in the way, or it is not. It is in the way. To count on an
intermediary, such as suggested by Jimmie, knife-edge propagation or
bend of the waves, is probably not in our student's syllabus. Besides,
I have seen neither you nor Jimmie offer the attenuation presented by
such refractions (and the attenuation is not marginal). Without
quantifiables, the path budget cannot be calculated.

The problem, as stated, has a clear answer in looking over the hill by
raising one antenna, the question informs us that is the answer and
that is simply resolved with trig (albeit, including the radius of
earth and accounting for its curvature).

73's
Richard Clark, KB7QHC

Might I recommend a program misleadlingly called Radio Mobile. This
piece of software will all let you check many real world situations.
This program is not real easy to use, it's a lot worse than Windows or
Office (ok, not worse than Office), but it is worth learning unlike the
previous 2 mentioned.

The site you need for the software is

http://www.cplus.org/rmw/english1.html

and then you need to download a large amount of terrain data, which is
freely available from NASA. It looks like the way this is handled has
changed since I did it last, so I can't comment on how it is done now.

tom
K0TAR

On Wed, 07 Feb 2007 22:24:26 -0600, Tom Ring
wrote:

The site you need for the software is

http://www.cplus.org/rmw/english1.html

and then you need to download a large amount of terrain data, which is
freely available from NASA. It looks like the way this is handled has
changed since I did it last, so I can't comment on how it is done now.

Hi tom,

I was involved in Beta testing this. The current version allows
dynamic map loading over the Internet, and overlays of Mapquest, Tiger
or many other mapping programs available. I've been using it heavily
for the last few months and its world of variables allows for finely
grained analysis. However, it also allows for massive headaches if
all you are looking for is a simple solution. In short, no
quantifiables are going to follow from your recommendation - unless I
do it. This lil Red Hen isn't interested in cooking that bread.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Wed, 7 Feb 2007 00:08:19 -0500, "Stefan Wolfe"
wrote:


"Richard Clark" wrote in message
. ..
On Tue, 6 Feb 2007 22:35:04 -0500, "Stefan Wolfe"
wrote:

2. The effect of the 80m hill 10Km away is negligible. The arc tan is
only
.008 degrees, thus the transmitter hardly "sees" it.

Actually, Stefan, the transmitter cannot see through it at all.

Exactly . And taking into account the 15 degree bend of the radio horizon
(even at 10 GHz) vs the arctan of .008 degrees for the the hill, reduced
somewhat by the 20 foot transmitter tower to .006 degrees, the hill
itself
is invisible at a 30km far field. The bend of the propagating waves which
extends the radio horizon clearly mitigates any possible effects of the
80m
hill.


Hi Stefan,

You seem to be simultaneously agreeing and disagreeing. The hill is
either in the way, or it is not. It is in the way. To count on an
intermediary, such as suggested by Jimmie, knife-edge propagation or
bend of the waves, is probably not in our student's syllabus. Besides,
I have seen neither you nor Jimmie offer the attenuation presented by
such refractions (and the attenuation is not marginal). Without
quantifiables, the path budget cannot be calculated.

The problem, as stated, has a clear answer in looking over the hill by
raising one antenna, the question informs us that is the answer and
that is simply resolved with trig (albeit, including the radius of
earth and accounting for its curvature).

73's
Richard Clark, KB7QHC

There are lots of programs out here for calculating path loss for LOS
situations but figuring in the path via knife edge defraction is something I
have always tried to avoid.. In real life there are too many variables that
effect this and you could have a signal that would tend to fade. Over the
years I have forgotten or lost interest in figuring the impractical.

Jimmie