# Calculating dB output from this example

This is my extra credit assignment so don't tell me answers, but please guide me how I should do this. I need to learn.

Question states: Determine the power output of the receiver in watts and in the appropriate measure of dB

let: Pin = 2W

diagram: --> [ G1 = 1/4 ] --> [ G2 = 1/10 ] --> [ G3 = 20 ] -->

How should I start?

After some thinking..

I'm not sure but G might represent the General formula which is G = Pout/Pin

EDIT

Is this correct?

Pin(dB) = 10log(2W/1W) = 3.01dB --- as input

dB = 10log(1/4) + 10log(1/10) + 10log(20) = -3.01dB --- As output

So the output at the destination is 0?

• What are G1, G2 and G3 and what are the numbers 1/4, 1/10 and 20 associated with them? – Chris Taylor Nov 30 '11 at 8:27

Hint: Search for transfer function and Bode Plot
• @HelpNeeder :D See, this is completely different from what you ask. OK, they are simple gain blocks in series hence you can multiply to obtain just one block and the $G$ blocks are processing the signal I suppose.Do you know how to calculate the power of the signal? – user13838 Nov 30 '11 at 18:05