Mountain/hill Bounce calculators
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Bob Larkin
Aug 13, 2018, 3:58:10 PM8/13/18
to PNW-Mi...@googlegroups.com
Experimenters, here is something for entertainment. For several years I
have been working with calculating the amount of signal received from
bounces off "mountains." This has resulted in a couple of on-line
calculators that seem to provide reasonable results. At this point I
would like others to try these out and report their data points.
If you go out and bounce a VHF/UHF/microwave signal off of an object,
like a hill or mountain (maybe a building), enter the data to the Web
"Calculator to Find Mountain-Bounce Radio Scattering Efficiency from
Measured Data"
http://www.janbob.com/electron/Calc_MtnBounce7.html
To use this you need the obvious station parameters and also an estimate
of the received power. This latter item is a good subject for separate
discussion, as there are several appropriate ways to find this. For
now, we assume you have a calibration from a signal generator, or have
figured the power from the observed S/N, or otherwise estimated the dBm.
The result of the calculator is a number I call Scattering Efficiency.
The gist of this is that there is some mountain area that is visible to
both stations. This intercepts some amount of power from the
transmitting station. 100% or 0dB scattering efficiency would result if
that total power was radiated by an isotropic radiator. In the real
world, much power is absorbed. Measurements on ice/rock mountains of
the Pacific Northwest US suggest values:
Rock/Ice mountain, stations on the same side: -15 to -25 dB
Rock/Ice mountain, stations at glancing angles: -25 to -40 dB
For reference, the Moon produces an efficiency in the range of -11 dB.
The second related web page is the "Calculator to Estimate
Mountain-Bounce Radio Transmission Loss (to Predict Received Signal Power)
http://www.janbob.com/electron/Calc_MtnBouncePredict5.html
This is what we would use to estimate the signal level to be received
for a particular bounce path. It assumes we have an idea of the
Scattering Efficiency.
One note: The observable part of the mountain is modeled as a triangle
with a variable included angle at the top and some height. The resulting
area is half the base times the height. All that is important is that
resulting area. If the triangle model is inappropriate, create a
triangle with the same area as the correct shape. Maybe this needs to
be changed to allow different shapes, or just an area input. Feedback
would be appreciated.
Let us know what you find!
Thanks and 73, Bob W7PUA
have been working with calculating the amount of signal received from
bounces off "mountains." This has resulted in a couple of on-line
calculators that seem to provide reasonable results. At this point I
would like others to try these out and report their data points.
If you go out and bounce a VHF/UHF/microwave signal off of an object,
like a hill or mountain (maybe a building), enter the data to the Web
"Calculator to Find Mountain-Bounce Radio Scattering Efficiency from
Measured Data"
http://www.janbob.com/electron/Calc_MtnBounce7.html
To use this you need the obvious station parameters and also an estimate
of the received power. This latter item is a good subject for separate
discussion, as there are several appropriate ways to find this. For
now, we assume you have a calibration from a signal generator, or have
figured the power from the observed S/N, or otherwise estimated the dBm.
The result of the calculator is a number I call Scattering Efficiency.
The gist of this is that there is some mountain area that is visible to
both stations. This intercepts some amount of power from the
transmitting station. 100% or 0dB scattering efficiency would result if
that total power was radiated by an isotropic radiator. In the real
world, much power is absorbed. Measurements on ice/rock mountains of
the Pacific Northwest US suggest values:
Rock/Ice mountain, stations on the same side: -15 to -25 dB
Rock/Ice mountain, stations at glancing angles: -25 to -40 dB
For reference, the Moon produces an efficiency in the range of -11 dB.
The second related web page is the "Calculator to Estimate
Mountain-Bounce Radio Transmission Loss (to Predict Received Signal Power)
http://www.janbob.com/electron/Calc_MtnBouncePredict5.html
This is what we would use to estimate the signal level to be received
for a particular bounce path. It assumes we have an idea of the
Scattering Efficiency.
One note: The observable part of the mountain is modeled as a triangle
with a variable included angle at the top and some height. The resulting
area is half the base times the height. All that is important is that
resulting area. If the triangle model is inappropriate, create a
triangle with the same area as the correct shape. Maybe this needs to
be changed to allow different shapes, or just an area input. Feedback
would be appreciated.
Let us know what you find!
Thanks and 73, Bob W7PUA
James C
Aug 13, 2018, 4:18:12 PM8/13/18
to Bob Larkin, PNW Microwave
Very cool Bob! Thanks for putting this together! .-James K7KQA DN06
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