It will plot the 0.6 Fresnel zone and the true radio path for a given value of K (the effective Earth radius factor).  This is all displayed in reference to the path's elevation data taken at intervals along the link path.  You can also place obstructions or trees along the way to let you know if you actually have a clear radio line-of-sight path.

Still (somewhat) experimental.

Using Your Own Data

To use your own data, you'll first need to hand enter the elevation and obstruction's height.

Yeah, I know, it sucks. Oh well.

Example of a Bad Link

Assumed :

TX Site Elevation : 185.00 m
TX Antenna Height : 8.00 m
RX Site Elevation : 180.00 m
RX Antenna Height : 15.00 m
    Path Distance : 20.00 km
(Everything else is default)

Path Distance Step     Ground Elevation     Obstruction/Tree Height
(kilometers)           (AMSL - meters)      (AGL - meters)

2	               185                  3   # small bush/tree thing
4                      184                  15  # large building
6		       188                  2   # small bush/tree thing
8                      188                  4   # small building
10                     175                  15  # really big monster !!
12                     170                  5   # UFO landing pad
14                     179                  30  # huge tree/cliff
16                     187                  2   # small bush/tree thing
18                     186                  8   # large building
19                     179                  1   # small bush/tree thing

Plot that as an example.  If everything goes right, you'll see a neat graphic showing a crappy RF path (Fresnel zones hit the ground).

You'll want to break the total path distance up into steps, say 0.1 to 1.0 kilometers, and find the ground elevation and obstruction height at those specific locations.

Do this for each point along your radio path, starting out, say 0.2 kilometers in front of the first (transmitter) antenna site. End with the total path distance, say 2.0 kilometers, MINUS a little bit (to keep from overwriting data) at the second (receiver) antenna site.

Example of a Good Link

Assumed :

TX Site Elevation : 180.00 m
TX Antenna Height : 13.70 m
RX Site Elevation : 186.00 m 
RX Antenna Height : 19.80 m
    Path Distance : 2.00 km
(Everything else is default)

Path Distance Step     Ground Elevation     Obstruction/Tree Height
(kilometers)           (AMSL - meters)      (AGL - meters)

0.2                    181                  3   # small bush/tree thing
0.4                    182                  9   # large building
0.6                    183                  2   # small bush/tree thing
0.8                    183                  4   # small building
1.0                    184                  1.5 # monster !!
1.2                    183                  5   # UFO landing pad
1.4                    181                  15  # huge tree
1.6                    184                  10  # tree thing
1.8                    185                  8   # large building
1.9                    186                  1   # small bush/tree thing

Notes

• Smaller step sizes for the elevation data are better.
• Elevation step sizes don't have to be equal.
• Use high quality, 7.5-minute topo maps or DEM data to get your elevation data.
• You could even use a GPS receiver and walk along the path plotting points.