Advanced Qualification · A-006 Receivers · A-006-005-006
Which of the following is an important reason for using a VHF intermediate frequency in an HF receiver?
- A To prevent the generation of spurious mixer products
- B To move the image response far away from the filter passband
- C To provide a greater tuning range
- D To tune out cross-modulation distortion
Correct answer: B — To move the image response far away from the filter passband. From the official ISED question bank, verified word for word.
Why
Using a very high intermediate frequency in an HF receiver pushes the unwanted image signal, which is a mirror frequency created during mixing, far enough away from the desired signal that the front-end filters can easily block it. The full explanation — and one for every question — is in Pro.
Practise this section
Receivers: superheterodyne design, selectivity, sensitivity, images, AGC and noise.