What condition may prevent a VHF radio...

🔍 Key Concepts

• Frequency synthesizer / PLL (Phase-Locked Loop) and how it holds the receiver on the selected channel • Difference between normal superheterodyne operation (local oscillator + IF) and a fault condition • What happens when the tuning control circuit in a synthesized VHF set fails or becomes unstable

💭 Think About

• Ask yourself: Which option describes a normal, correct behavior in a superheterodyne receiver rather than a fault? Eliminate that first. • Which circuit is specifically responsible for locking the receiver onto the exact channel frequency in a modern synthesized VHF set? • If that circuit stopped working correctly, what would you notice about the set’s ability to stay on frequency or to hold the selected channel?

✅ Before You Answer

• Identify which options describe standard receiver functions (these are usually NOT the cause of a tuning failure). • Focus on the role of the PLL / frequency synthesizer in channel selection and stability. • Before choosing, be sure the condition you pick would actually cause the receiver to lose lock or drift off the desired channel, not just process the audio.

What condition may prevent a VHF radio receiver from staying tuned to the desired channel?

The local oscillator frequency is beating against the incoming signal to produce an Intermediate Frequency (IF).

The output signal of the Phase Locked Loop ( PLL ) circuit in the frequency synthesizer has become unlocked .

The discriminator circuit is alternately developing positive and negative voltages at the modulation frequency.

The ratio detector circuit is producing a variable output that deviates across the receiver's dynamic range.

🔍 Key Concepts

💭 Think About

✅ Before You Answer