Which of the following conditions could...

🔍 Key Concepts

• MF/HF transmitter signal path from power supply → oscillator/PLL → modulators/filters → RF power amplifier → antenna/load • Difference between RF power being generated and RF energy being radiated (dummy load vs antenna) • Purpose of a crowbar protection circuit in a power supply and what happens to the transmitter stages when it operates

💭 Think About

• For each option, ask: would the RF power amplifier still be powered and capable of generating RF, or would something prevent any RF from being produced at all? • Think about what a dummy load does in a radio test setup: does it stop RF from being made, or just stop it from going out over the air? • Consider what happens to every stage of the transmitter if the power supply suddenly clamps or shorts to protect against overvoltage. Would the RF output meter see anything?

✅ Before You Answer

• Verify which option would remove or cut off DC power from the RF stages entirely, resulting in no RF generation. • Check which options affect only signal quality or routing (filtering, feedback, where the RF goes) but not necessarily whether RF is generated. • Make sure you distinguish between zero RF at the transmitter output connector vs no radiation from an antenna, and what the question is specifically asking about.

Which of the following conditions could cause zero RF output in a MF/HF transmitter operating in the F1B FEC mode?

The connection of a transceiver is connected to a "Dummy Load" antenna.

The failure of the voice bandpass filter in the stage preceding the RF amplifier.

The activation of a " crowbar " circuit in the power supply to prevent an unregulated voltage increase .

The generation of a positive VCO feedback signal to a Phase Locked Loop circuit in the transmitter.

🔍 Key Concepts

💭 Think About

✅ Before You Answer