On 9 Jan 2005 14:06:22 -0800, "jetfixr" wrote:

I recently took a test and I failed to understand how the answered was
derived.. Heres the question:

A malfunctioning transmitter designed to transmit at 28 watts of power
has a power output of 7 watts. In its current state, its signal is
being received by a base station at 5uV. If the transmitter were to be
repaired and had its proper output of 28 watts, what would the receive
signal signal at the base station be?

I figured if the transmitter were repaired, that would be a improvement
of 6dB on the transmit side. At the receiver I would figure the signal
should be 20uV, but somehow the the correct answer was a receive signal
of 10uV. I have no idea how they derived 10 uV and no explaination was
given. Can someone help me out with the math here?

You are over complicating things. According to ohms law, whenever you
double the voltage, (and resistance remains the same) the current
must also double so your power quadruples. For example,

10 Volts / 5 Ohms = 2 Amps Power = 10 V x 2 A = 20 Watts

20 volts / 5 Ohms = 4 Amps Power = 20 V x 4 A = 80 Watts

So taking it in reverse, if you power quadruples from 7 Watts to 28
Watts, the voltage in you example doubles from 5 uV to 10 uV.