Here is a simple table of path loss calculations in free space for channel 1 with clear line of sight (the difference in path loss from channel 1 to channel 11 is negligible). See Chapter 6 shows how to use these numbers to figure out how far your network can reach. Distances are in miles; losses are in dB.
|
Distance (in miles) |
Losses on channel 1 (in dB) |
|---|---|
|
0.5 |
98 |
|
1 |
104 |
|
2 |
110 |
|
3 |
114 |
|
4 |
116 |
|
5 |
118 |
|
7 |
121 |
|
10 |
124 |
|
15 |
128 |
|
20 |
130 |
|
25 |
132 |
|
30 |
134 |
The path loss table above was calculated with the following formula, rounded up to the nearest whole number:
| L = 20 log(d) + 20 log(f) + 36.6 |
Check out ARRL online (http://www.arrl.org) for what might be the most authoritative source of radio information on the planet. Their excellent books (in particular, UHF/Microwave Experimenter’s Manual and The ARRL Antenna Book) are the definitive sources for learning about microwave communications.