Question 1A5

Frequency tolerance is expressed in parts per million (ppm), meaning a deviation of a certain number of Hertz for every million Hertz of the nominal frequency. The "legal tolerance" for frequencies like the VHF marine band (where 156.800 MHz and 156.525 MHz reside) is commonly 10 ppm for low-power transmitters. The 2 ppm accuracy of the frequency counter describes its measurement precision, not the operational legal tolerance itself. To calculate the allowed deviation at 10 ppm: * For 156.800 MHz: 156,800,000 Hz * (10 / 1,000,000) = 1568 Hz or 1.568 kHz. * Allowed range: 156,800.000 kHz ± 1.568 kHz = 156,798.432 kHz to 156,801.568 kHz. * For 156.525 MHz: 156,525,000 Hz * (10 / 1,000,000) = 1565.25 Hz or 1.56525 kHz. * Allowed range: 156,525.000 kHz ± 1.56525 kHz = 156,523.43475 kHz to 156,526.56525 kHz. Checking the frequencies in option A: * 156,798.758 kHz is within the range [156,798.432, 156,801.568] kHz. * 156,526.243 kHz is within the range [156,523.43475, 156,526.56525] kHz. Both frequencies in option A fall within the 10 ppm legal tolerance, making A the correct answer. The other options contain frequencies that deviate by more than 10 ppm from their nominal values.