Convert Power to a Peak Voltage, when to multiply by sqrt(2)

  • #1
I have a dBW value and dBW I understand to normally be given as representing a RMS Power (however this is not specificically ever stated and I am told its just assumed?)

from dBW to Watts = 10^(dBW/10)
This then gives RMS power in Watts

At what point do I convert this from a RMS to a peak value:

1. Multiply RMS Power in Watts by sqrt(2) before using Voltage = sqrt(Power*50)
2. Or multiply the result from Voltage = sqrt(Power*50) by sqrt(2)

because they give two different values...
 

Answers and Replies

  • #2
Averagesupernova
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There is really no such thing as RMS power. No matter what audio power amplifier salespeople tell you, power is always average, or if so spec'd, peak. Do not multiply power by 1.414. To convert the power of a sine wave from average to peak, you need to compute the voltage, multiply that by 1.414, then convert back to power. You will find that with a sine wave, peak power is double average power.
 
  • #3
sophiecentaur
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from dBW to Watts = 10^(dBW/10)
This then gives RMS power in Watts
etc.
This may sound a bit lame but what is the context of your question? It seems to me that you may be talking about an RF signal which is varying in level (Amplitude Modulation?). The 50 figure suggests a 50Ω RF system. The arm-wavey use of the term "RMS Power" has different meanings and differently fuzzy use in RF and Audio.
and I am told its just assumed?
That proves my point! If it really means something then they would come clean and define it properly.
Power is Power. The Average power over time for a signal is just that. How that can be calculated must depend on the details of the system in question.
1. and 2. are confusing me a bit.
Try explaining the context of all this. It should become clear.
 

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