[sdiy] doh!

[Tim Ressel]

Ian,

Thanks for the correction. Indeed, I meant to make the
point that the third letter denotes the reference.

Let me add that different displines have different
references. In RF land, dBm means 1mW into 50 ohms.

I believe my point has been made: Know the reference
when doing dBs!!

--TR

--- Ian Fritz <ijfritz at earthlink.net> wrote:
> At 01:45 PM 10/23/2002, media.nai at rcn.com wrote:
> 
> >dBu is dB referenced such that .775V into 600 Ohm
> is 1 mW, and Decibels are
> >logarithmic so
> >
> >dBu = 20 log (Vrms/0.7746) and
> >
> >Vrms = .707Vpk  (Vpk = Vp-p/2)
> 
> I don't believe this is quite correct. What you are
> describing is dBm, not 
> dBu. Just remember that the "m" refers to a
> "m"illiwatt (into 600 Ohms).
> 
>    Ian
> 


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