1. What is Duty Cycle?

The duty cycle represents the percentage of time a radio is transmitting during a complete transmit-receive cycle. For the Yaesu FT-991, monitoring duty cycle is important to prevent overheating and ensure optimal performance.

2. How Does the Calculator Work?

The calculator uses the duty cycle equation:

Where:

• Transmit Time — Duration of transmission in seconds
• Total Cycle Time — Complete cycle time (transmit + receive) in seconds

Explanation: The equation calculates what percentage of the total cycle time is spent transmitting.

3. Importance of Duty Cycle Calculation

Details: Knowing your duty cycle helps prevent radio damage from excessive transmission times. The FT-991 has specific duty cycle limitations that should not be exceeded for prolonged periods.

4. Using the Calculator

Tips: Enter both transmit time and total cycle time in seconds. Transmit time cannot exceed total cycle time. Values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a safe duty cycle for the FT-991?
A: While the FT-991 can handle 100% duty cycle briefly, sustained operation should generally stay below 50% for SSB and 20% for digital modes.

Q2: How does duty cycle affect radio temperature?
A: Higher duty cycles generate more heat. The FT-991's cooling system is designed for typical amateur use, not continuous high-power transmission.

Q3: Does duty cycle calculation differ by mode?
A: Yes. SSB has lower duty cycle than FM or digital modes because of its lower average power during speech pauses.

Q4: How can I reduce my duty cycle?
A: Use lower power settings, take breaks between transmissions, and alternate between transmit and receive periods.

Q5: Why is my FT-991 shutting down during long transmissions?
A: This is likely thermal protection kicking in due to excessive duty cycle. Allow the radio to cool and reduce your transmission times.