Appendix B. Path Loss Calculations

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.