Padders in receivers: In a radio receiver, what is the function of padders?

Introduction / Context:
Padders are small capacitors used in the local oscillator or tuning circuits of radio receivers. They play a crucial role in ensuring the oscillator and RF stages track each other correctly across the frequency band.

Given Data / Assumptions:

• Receiver uses superheterodyne design.
• Tracking means maintaining a fixed IF difference between the RF and LO frequencies across the entire band.

Concept / Approach:

Because the tuning capacitance vs. frequency relationship of RF and LO circuits may not match perfectly, padders are added to adjust (pad) capacitance in the LO circuit, ensuring proper alignment and tracking across the band.

Step-by-Step Solution:

Verification / Alternative check:

Radio servicing manuals confirm that padders are adjusted during alignment to ensure RF and LO stages track properly.

Why Other Options Are Wrong:

• Discard the carrier: function of detector, not padders.
• Filter input signal: done by RF filters.
• Suppress noise: handled by AGC and filtering.
• Provide impedance matching: padders are not for matching.

Common Pitfalls:

• Confusing padders with trimmers (used for fine adjustment).

Final Answer:

Facilitate tracking