🔍 Key Concepts

• Voltage Controlled Oscillator (VCO) function inside a VHF synthesizer • How a Phase-Locked Loop (PLL) keeps a transmitter on the correct frequency • Typical symptoms when a radio is off-frequency / loses lock vs when it just has power-output issues

💭 Think About

• Ask yourself: if the VCO stops working properly, what happens first – the accuracy/stability of the frequency, or the transmitter power level? • Which of these choices directly involves the frequency control loop rather than just the strength or width (deviation) of the signal? • When a PLL can’t keep the oscillator locked to the reference, what kind of fault/indication would the synthesizer circuitry be designed to detect or report?

✅ Before You Answer

• Identify which option refers to the frequency control system (PLL/VCO) rather than audio level or RF power level. • Decide whether VCO failure would be more likely to cause frequency instability/off-frequency conditions or only change the transmitter’s power level. • Eliminate any options that talk only about output power or modulation depth without mentioning the frequency-control mechanism.