Determine RF power output

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ejleiss

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Hello,

I am playing around with an RF transmitter and I am looking at the output carrier wave on a signal analyzer. The output on the analyzer is measuring -7dBm. If someone were to ask what is the RF output power level, how do I explain this in terms on mW or Watts?

Thanks
 

mW = 10^(dBm/10)
dBm = 10 * log(mW/1mW)
 

-10 dBm is 0.1 milliwatt. 0 dBm is 1 milliwatt. 30 dBm is 1000 milliwatts or 1 watt. a 3 dB difference doubles, or halves, the power.

So starting at -10 dBm, and going up 3 dB to -7 dBm, means you have double of 0.1 milliwatts, or 0.2 milliwatts.

Now, you have to be careful when using a signal analyzer to measure power. If there is modulation, you must open up the measuring system's bandwidth to include most of the modulation width. You are not just looking for the peak of the waveform you see on the screen, but need the instrument to "integrate" ALL of the power there vs frequency.
 

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