Chapter 11 / 11.10 / 11.10.2

11.10.2 Why Do Radio Waves Become Weaker AS They Travel?

Signals become progressively weaker with increasing distance, even in perfect free space. This FAQ explains spherical spreading, free-space loss, effective isotropic radiated power (EIRP), antenna aperture, and the Friis transmission equation, showing why signal strength decreases and how antennas help overcome this loss.

1. Why Doesn't a Radio Signal Maintain the Same Strength?
2. Is Energy Being Lost?
3. Why Does Signal Strength Follow the Inverse-Square Law?
4. What Is Free-Space Loss?
5. What Is Power Density?
6. Why Do Antennas Matter?
7. What Is EIRP?
8. What Is the Friis Transmission Equation?
9. Why Do Higher Frequencies Appear to Have Greater Path Loss?
10. How Does This Affect Communication-System Design?
11. Why Is Understanding Free-Space Path Loss So Important?
12. What Should You Remember?

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