| Earth
Bulge |
As the distance
between two points increase, so does the curvature of
the earth. This is called the earth bulge...
When planning a long microwave link,
the size of the Earth bulge must be considered.
The Earth bulge formula:
Lets break it apart....
The Height of the Earth bulge in feet
equals the Distance in miles between the two antennas,
squared, divided by 8.
Example: The
distance between two proposed antenna sites is 10 miles.
10 ^2 = 100
100 / 8 = 12.5
The size of the bulge at 10 miles in
the center is 12.5 feet.
Antenna height must be adjusted to overcome
this. |
| Antenna
Height |
So, we know
the size of the fresnel zone and the earth bulge, now
what?
Add the two together to form the minimum
antenna height...
Keep in mind the MINIMUM height is 60%
of the fresnel zone divided by two, plus the earth bulge.
Don't forget to
figure in the trees or any other obstruction in the
height the antennas need to be !!!....
One more formula... |
|
