Question E9A03:
What term describing total radiated power takes into account all gains and losses?  

Choices:  
A: Power factor  
B: Half-power bandwidth  
C: Effective radiated power  
D: Apparent power    

Correct Answer is  C: Effective radiated power  

Correct answer: C — Effective radiated power

1) Why it’s correct
- Effective Radiated Power (ERP) is the transmitter output power after accounting for system losses and antenna gain, referenced to a half-wave dipole. It represents the “total radiated power” in the direction of maximum radiation, including all gains and losses.

2) Why the others are incorrect
- A: Power factor — An AC power term (ratio of real to apparent power). Not about radiation.
- B: Half-power bandwidth — Frequency range over which the response is within −3 dB of peak. Not a power accounting term.
- D: Apparent power — AC quantity $S = V_{\text{rms}} I_{\text{rms}}$ (in VA). Not radiated power.

3) Useful formulas and rules
- Linear form:
  $$\text{ERP} = P_{\text{out}} \times G_{\text{ant, lin (dBd)}} \times \eta_{\text{system}}$$
  where $P_{\text{out}}$ is transmitter output, $G_{\text{ant}}$ is antenna gain relative to a dipole, and $\eta_{\text{system}}$ includes feedline/connector/mismatch losses.

- dB form (common in practice):
  $$\text{ERP}_{\text{dBW}} = P_{\text{out,dBW}} + G_{\text{dBd}} - L_{\text{dB}}$$

- Related term (often tested): EIRP, referenced to an isotropic radiator
  $$\text{EIRP}_{\text{dBW}} = P_{\text{out,dBW}} + G_{\text{dBi}} - L_{\text{dB}}$$
  $$G_{\text{dBi}} = G_{\text{dBd}} + 2.15\ \text{dB}, \quad \text{EIRP}_{\text{dBW}} = \text{ERP}_{\text{dBW}} + 2.15\ \text{dB}$$

- Rules of thumb:
  - +3 dB ≈ 2× power
  - +10 dB = 10× power
  - −3 dB ≈ 1/2 power (the “half-power” point)