[Elecraft] OT: math question

[Tom Hammond]

At 12:01 PM 3/30/05, you wrote:
>How would one calculate the amplifier gain (in dB) required to go from one
>power level to another?  For example from 5W to 100W.

10 log(P2/P1) = 10 log(100/5) = 10 log(20) = 10 (1.30103) = 13.0103dB

An easy 'rule of thumb' way to get a good idea of such levels
is to remember that:

   a power INcrease of 2  = approx. +3dB change
   a power DEcrease of 2  = approx. -3dB change

   a power INcrease of 10 = +10dB
   a power DEcrease of 10 = -10dB

So, to go from 5W to 10W output, you have 3dB GAIN
     to go from 10W to 100W, you have 10dB gain

Since dB's can be added, going from 5W to 100W = 3db + 10 dB = 13dB

Similarly, if you went from 2W to 800W...

   From 2W to 4W (first doubling of power) =  +3dB
   From 4W to 8W (2nd doubling of power)   =  +3dB
   From 8W to 800W (increase of 10X)       = +10dB
                                           -------
    Total power increase in dB     =         +16dB

73,

Tom Hammond   N0SS