[Elecraft] OT: math question

[Tom Hammond]

Hi Frank:

Thanks pal... guess I got a bit ahead of myself there!

Of course, you're completely correct! Should have been 26db, instead of 16dB!

73,

Tom

At 03:54 PM 3/30/05, you wrote:
>Hi Tom,
>Just a small correction to your 2W to 800W example:
> From 2W to 4W (first doubling of power) =  +3dB
> From 4W to 8W (2nd doubling of power) =  +3dB
> From 8W to 80W (increase of 10X) = +10dB
> From 80W to 800W (increase of 10X) = +10dB
>Total = 3+3+10+10 = 26db
>
>Best 73,
>Frank - W6NEK
>
>----- Original Message ----- From: "Tom Hammond" <n0ss at earthlink.net>
>To: <Able2fly at aol.com>; <elecraft at mailman.qth.net>
>Sent: Wednesday, March 30, 2005 11:01 AM
>Subject: Re: [Elecraft] OT: math question
>
>
>>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
>>
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