Question T5B11
From subelement T5 - T5B
Which decibel value represents a power increase from 20 watts to 200 watts?
Why is this correct?
A power increase from 20 watts to 200 watts represents a 10:1 ratio (200÷20=10). In decibels, +10 dB corresponds exactly to a 10:1 power ratio. The other answers don't match this fundamental relationship: 12 dB would represent roughly a 16:1 ratio, 18 dB about 63:1, and 28 dB over 600:1. Remember the key decibel benchmarks: +3 dB = 2:1 ratio, +6 dB = 4:1 ratio, and +10 dB = 10:1 ratio.
Memory tip
Pattern recognition tip: When calculating dB for power ratios, first find the simple mathematical ratio by dividing the larger number by the smaller. Then match it to the standard dB values: 2:1 = 3 dB, 4:1 = 6 dB, 10:1 = 10 dB. These three ratios solve most amateur radio decibel questions.
Learn more
In amateur radio operations, understanding these power ratios helps evaluate antenna gain, amplifier performance, and signal path losses. A 10 dB power gain is significant—it represents the difference between a 20-watt mobile radio and a 200-watt base station. When discussing RF system performance with other operators, these decibel relationships become second nature for comparing equipment specifications and calculating link budgets in repeater and EME communications.
Think about it
Why do you think amateur radio operators prefer using decibels instead of just saying 'ten times more power' when discussing equipment performance?