Question T0C02
From subelement T0 - T0C
At which of the following frequencies does maximum permissible exposure have the lowest value?
Why is this correct?
50 MHz has the lowest Maximum Permissible Exposure (MPE) limits because the human body absorbs RF energy most efficiently at this frequency. The wavelength at 50 MHz is about 1.5 meters (5 feet), which closely matches typical human height, making our bodies effective antennas. At both higher and lower frequencies, human bodies absorb less RF energy, so the exposure limits are less restrictive.
Memory tip
Remember the 'human antenna resonance' concept: when wavelength matches body dimensions, absorption peaks. This principle applies across RF safety questions—look for frequencies where physical dimensions create resonance effects. The 6-meter band (50 MHz) is uniquely hazardous for this reason.
Learn more
In practical station operation, 6-meter operators must be especially vigilant about RF exposure compliance due to these restrictive MPE limits. This frequency band requires careful antenna placement and power calculations. The FCC's frequency-dependent exposure standards reflect biological research showing peak absorption rates vary significantly across amateur frequency privileges, with VHF frequencies presenting unique challenges for station RF exposure evaluations.
Think about it
Why do you think antenna manufacturers often specify different minimum safe distances for 6-meter antennas compared to HF or UHF antennas of similar power ratings?