4. Solving the formula for dB loss. A transmission line is shown in Figure 3-9. The input power to the line is
1 milliwatt (mW) and the output power is .5 mW. It is easy to see that this line causes a power loss of 50
percent. But what is the dB loss? You can use the formula to find out.
Number of dB = 10 x log P2 (larger power)
P1 (smaller power)
dB= 10 x log 1
Dividing 1 by .5 you get 2 as the result. This gives:
dB = 10 x log 2
Figure 3-9. Transmission line with 50 percent power loss.