[Amps] Watts to DBM??

[Dr. David Kirkby]

Han Higasa wrote:
> hi Andy
> 
> 1W = 0 dBW = 1000mW = 30 dBm
> 
> A [dBm] = 10 x log (P) 
> 
> where P is power in milliwatts.
> 
> P [mW] = 10^(A/10)  = (A/10)th power of ten
> 
> whare A is power in dBm.
> 
> 3 dBm = 10^0.3 = approx 2 mW
> 10 dBm = 10^1 = 10 mW
> 
> de Han JE1BMJ

Han,

you seem to be the only one to answer the original question directly.

I would have added however that the log needs to be to the base 10, and not base 
e. Depending on what software you use to do the computation, the 'log' function 
may assume different bases.

Mathematica for example, assumes base e.

In[3]:= Log[1000.0]

Out[3]= 6.90776

and one needs to tell it to use base 10 if one wants base 10, as one would in 
this case.

In[4]:= Log[10,1000.0]

Out[4]= 3.

So does the free open-source Sage maths software.

http://www.sagemath.org/

IIRC, most calculators use the 'log10' button for log to the base 10.

dave