What is the Maximum Range I Can Get?

ab cd

Senior Member
The Maximum Range achievable at any location depends on
(1) Curvature of earth
(2) The terrain around that location. Terrain plays a very important role as hills & changes in ground level will restrict maximum range.

This is due to the fact that propagation of radio waves in GHz/Microwave range is line of sight. The range is therefore limited by curvature of earth, and is about 250 nautical miles / 450 km for an ideal condition of perfectly level terrain. Hills & rise in ground levels further restrict maximum range to less than 250 nautical miles / 450 km.

In order to determine what maximum possible range you can get at your location, follow the steps below:
(1) Visit the site http://www.heywhatsthat.com
(2) Select tab "new panorama"
(3) Enter your latitude and longitude
(4) Enter your elevation (=enter elevation of your antenna)
(5) Enter title
(6) Hit "submit request" button
(7) Wait and view sponsor's advertisement while panorama is generated
(8) When panorama is generated, scroll down to map, and click "up in the air" tab on top right of map.
(9) Zoom-out the map till you see two circular curves in blue & yellow colors, showing maximum distance of aircrafts at 10,000 feet & 30,000 feet elevation.
(10) Below the map you will see text boxes light yellow & light blue with default aircraft heights 10,000 feet & 30,000 feet. Change these to suite your requirements, and press "Enter" button. The two curves will modify to new height figures you have entered. Since commercial planes normally fly 45,000 feet and below, I use 45,000 feet for high flying planes (outer blue range curve) and 10,000 feet for low flying planes (inner yellow range curve).

tmp_22478-heywhatsthat terrain range-576492644.png

The layers of air cause refraction of radio waves, and radio line of sight may extend beyond optical line of sight by as much as 50 to 100 nautical miles. Your maximum possible range will therefore be about 50 to 100 nautical miles more than the maximum possible range shown by the curves you got from heywhatsthat.com site.

Physical Horizon vs Radio Horizon.PNG

To achieve your maximum possible range, your antenna should be installed at a height where it is above trees & houses surrounding it, and can "see" the horizon.

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ab cd, do you know if there is something similar to this? Heywhatsthat doesn´t work above 60 North. :(
There may be more sites like heywhatstha, but unfortunately I am not aware of these.

There is another site "Radio Mobile" for range plotting, but it is not totally based on geography/topology of terrain, but also takes into consideration receving system's electrical parameters.


Martin has done a range plot for my location. You can see details here:

I am posting below my range plot done by Martin.

Thank you very much ab cd! I will try that one and see what it say. How does it compare for you with heywhatsthat?
Thank you very much ab cd! I will try that one and see what it say. How does it compare for you with heywhatsthat?
Both the "Radio Moble" plot & "heywhatsthat.com" plot fit closely to my actual VRS plot, if in the heywhatsthat.com I enter plane height 40,000 feet in the blue text box at bottom right of "Up in the Air" map.