Why is it important to know the duty cycle of the mode you are using when transmitting?

Duty cycle refers to the percentage of time a transmitter is actively producing full RF power during a transmission. Different operating modes have vastly different duty cycles. Modes like FM or digital modes (such as FT8, RTTY, or PSK31) have a 100% (continuous) duty cycle, meaning the transmitter operates at full output power the entire time the push-to-talk is engaged. Conversely, CW and SSB voice have much lower duty cycles (around 40-50% or less) because power is only transmitted during key-down intervals or voice peaks. Many modern transceivers are only rated for continuous operation at lower power levels. If you transmit a 100% duty cycle mode at your radio's maximum rated SSB power, you risk overheating and permanently damaging the transmitter's final amplifier.