ASVAB (Armed Services Vocational Aptitude Battery)Electronics Information (EI)Hard
A client observes that their older analog radio receiver produces a high-pitched 'whistle' or 'howl' when tuned to certain frequencies, especially when near another strong radio signal. This interference is most likely caused by which of the following phenomena?
- AElectromagnetic Pulse (EMP)
- BThermal Noise
- CIntermodulation Distortion
- DStatic Discharge
Show answer & explanationAnswer & explanation
Correct answer: C. Intermodulation Distortion
Intermodulation distortion occurs when two or more signals mix non-linearly in a receiver, creating new, unwanted frequencies (intermod products) that can manifest as whistles or other forms of interference, especially in older or poorly designed receivers.
Why the other options are wrong
- A. EMP is a brief burst of electromagnetic energy that can damage electronics, not a continuous whistling interference.
- B. Thermal noise is random electronic noise, usually heard as a hiss or broadband static, not a distinct whistle at specific frequencies.
- D. Static discharge is a momentary electrical discharge, typically causing a crackle or pop, not a sustained whistle.
Intermodulation Distortion (IMD)
The generation of new, unwanted frequencies (intermod products) when multiple signals are amplified or processed non-linearly.
- Caused by non-linear components in a system.
- Results in spurious signals outside the original signal bandwidth.
- Often heard as whistles, clicks, or garbled audio in radio receivers.
Memory trick: Whistling signals are Often IMD's song.