Question

To measure radio frequency, the suitable frequency meter is

• A. Weston frequency meter
• B. reed vibrator frequency meter
• C. Hetrodyne frequency meter
• D. Electrical resonance frequency meter

Hint:

Heterodyning is a fundamental technique in radio communications.
It down-converts a high-frequency RF signal to a lower, easily measurable intermediate or audio frequency.
This principle is key to RF frequency meters.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks to identify the appropriate type of frequency meter used to measure high-frequency radio waves (RF range).

Step 2: Detailed Explanation:

• Frequency meters are designed to operate over specific frequency bands:

• Weston Frequency Meter: A deflection-type meter operating on magnetic principles, limited to low power-system frequencies (typically $45-55\text{ Hz}$).

• Reed Vibrator Frequency Meter: Uses mechanical resonance of steel reeds, limited to low power-system frequencies ($50\text{ Hz}$ or $60\text{ Hz}$).

• Electrical Resonance Frequency Meter: Uses tuned LC circuits, suitable for low to medium audio frequencies.

• Heterodyne Frequency Meter: Operates by mixing (heterodyning) the unknown high-frequency radio signal with a highly stable, adjustable reference frequency from an internal local oscillator. This mixing produces a low-frequency beat note. When the reference matches the unknown frequency, the beat frequency becomes zero (zero-beat condition). This method is highly accurate and is the standard way to measure high radio frequencies.

• Thus, the heterodyne frequency meter is the suitable choice for the radio-frequency spectrum.

Step 3: Final Answer:
The heterodyne frequency meter is suitable for measuring radio frequencies.