FCC Technician Exam Question Of The Day (T0C10)

Q) Why is duty cycle one of the factors used to determine safe RF radiation exposure levels?

A) It affects the average exposure of people to radiation

NJ2X Notes:
Non-Ionizing Radiation Warning Symbol
A duty cycle is the time that a device spends in its active state as a fraction of the total time under consideration.  In an amateur radio and RF safety context, the term is used with reference to transmitters.  Different operating modes have different duty cycle characteristics since the RF being radiated is often intermittent.  A lower duty cycle reduces the average exposure to the RF radiation. 

Examples of operating mode typical duty cycles:
  • CW           = 40%
  • SSB voice = 20%
  • FM            = 100%
Duty cycle is used to determine average power.  Here is the formula:

      Average power = PEP x operating cycle x (transmitting time / averaging period)


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