*Question G8A13:
What is a link budget?*  

*Correct Answer is  C: The sum of transmit power and antenna gains minus system losses as seen at the receiver*  

### AI Response: (may contain errors)  

A link budget is a crucial concept in radio communications that helps engineers and operators understand the performance of a radio link. 

### Correct Answer Explanation:
**C: The sum of transmit power and antenna gains minus system losses as seen at the receiver** is correct because:

- A link budget accounts for all the gains and losses in a communication system from the transmitter to the receiver.
- It includes:
  - **Transmit Power ($P_T$)**: The power output from the transmitter.
  - **Antenna Gains ($G_T$ and $G_R$)**: The gains from the transmitting and receiving antennas.
  - **System Losses ($L$)**: Any losses due to the environment, cables, connectors, and other factors.

The formula for a basic link budget can be expressed as:

$$
P_R = P_T + G_T + G_R - L
$$

where:
- $P_R$ = received power
- $P_T$ = transmit power
- $G_T$ = gain of the transmitting antenna
- $G_R$ = gain of the receiving antenna
- $L$ = total system losses

### Incorrect Answer Explanations:
- **A: The financial costs associated with operating a radio link**  
  This choice is incorrect because a link budget does not involve financial considerations; it focuses on the technical aspects of signal strength and losses.

- **B: The sum of antenna gains minus system losses**  
  This is incorrect because it omits the transmit power. A complete link budget must include the transmit power to determine the received signal strength accurately.

- **D: The difference between transmit power and receiver sensitivity**  
  This choice is misleading. While receiver sensitivity is important for determining if the received signal is adequate, a link budget encompasses more than just this difference. It includes all gains and losses in the system.

### Summary:
Understanding the link budget is essential for ensuring that a radio link can successfully transmit and receive signals. It helps in designing systems that meet the required performance criteria.