FCC Exam Question: 6A404

An advantage of link coupling between RF amplifier stages is:

A. The flexibility of mechanical construction possible
B. Reduction of tube capacitance effects on the L/C ratio of the tank circuits
C. Both A and B
D. Neither A or B
Correct Answer: C

Explanation: Link coupling utilizes a small, separate coil (the link) that is inductively coupled to the main tank circuit coil. This provides significant mechanical flexibility (A) because the link coil can be easily positioned, rotated, or even remotely located from the tank circuit itself, simplifying chassis layout and adjustments compared to direct connections or fixed taps. Furthermore, link coupling helps reduce the impact of tube (or transistor) capacitance on the tank circuit's L/C ratio (B). By coupling via the link, the active device's parasitic capacitance is not directly shunted across the *entire* resonant portion of the tank circuit. The link effectively transforms the impedance, isolating the primary L/C components from the full effect of the device's capacitance, allowing for a higher Q and more stable resonance. Therefore, both A and B are distinct advantages.

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Includes Elements 1, 3, 6, 7R, 8, and 9.