# Element 3D Question 152

## Question:

 [EL3D-152] What would be the dB change in field intensity at a given distance if the transmitter output power is doubled? a} 1.5 dB. [Correct Answer] b} 6 dB. c} 2 dB. d} 3 dB.

## Challengers Excerpt:

What would be the dB change in field intensity at a given distance if the transmitter output power is doubled?

I believer the answer is wrong seeing that every other book and knowledge shows that it is 3dB.

## Response:

Your analysis is correct.  I believe the intent of this question was to ensure you are aware that a doubling of power would result in an increase of approximately 1.5 [1.414] of the field intensity.  Field intensity is typically measured in mV/m or dB/uV..  Today's spectrum analyzers would display the correct change in dB/uV if the source doubled in power.  The approximate 1.5 times increase would be for the mV/m figure.

e.g.  Assume a 50 ohm impedance.  1 mW would be 0.2236 V.  2 mW would be 0.3162 volts.  Doubling the power only increased the voltage by 1.414 [approximately 1.5].

## Recommendation:

Change the question to:

 [EL3D-152] What would be the change in field intensity [mV/m] at a given distance if the transmitter output power is doubled? a} 1.5 times.  [Correct Answer] b} 6 times. c} 2 times. d} 3 times.