*Question G8B05:
Which intermodulation products are closest to the original signal frequencies?*  

*Correct Answer is  C: Odd-order*  

### AI Response: (may contain errors)  

To understand why the correct answer is "Odd-order" intermodulation products, let's break down the concepts involved.

### Correct Answer: Odd-order

- **Odd-order intermodulation products** are generated from the mixing of two or more signals and are typically found at frequencies that are close to the original signal frequencies. 
- For two signals with frequencies $f_1$ and $f_2$, the odd-order products can be expressed as:
  - $f_1 + f_2$ (1st order)
  - $f_1 - f_2$ (1st order)
  - $2f_1 - f_2$ (3rd order)
  - $2f_2 - f_1$ (3rd order)
  
These products are generally closer to the original frequencies compared to even-order products.

### Why the Other Choices are Incorrect:

- **A: Second harmonics**
  - Second harmonics are simply multiples of a single frequency (e.g., $2f_1$). They do not involve mixing two different signals and are not considered intermodulation products.

- **B: Even-order**
  - Even-order intermodulation products (like $2f_1 + 2f_2$) are further away from the original frequencies compared to odd-order products. They tend to be at higher frequencies and are less likely to interfere with the original signals.

- **D: Intercept point**
  - The intercept point is a measure of a system's linearity and does not refer to specific intermodulation products. It indicates the point where the gain of the fundamental signal and the intermodulation products intersect on a graph, but it does not describe the frequency characteristics of the products themselves.

### Summary

- Odd-order intermodulation products are closer to the original signal frequencies due to their mathematical generation from the mixing of signals.
- Even-order products and second harmonics are either further away or not related to intermodulation mixing.
- The intercept point is a concept related to system performance, not the frequencies of intermodulation products.

This understanding will help you answer questions related to intermodulation products effectively on the Extra Class exam.