"Telamon" wrote in message
...
Absolute scales would be dBV, dBuV, and dBm. In those terms the
reference is 1 volt, 1 micro-volt (0.000001 volt), and 1 milliwatt
(.001 watt).

The reason you need a reference value is noise prevents you from
measuring 0 Volts and 0 watts accurately so you need to use a small
reference value in its place and so everyone agreed to use these
values.

Given you are discussing use of the dB, I think the above leaves a bit out.
You can't use 0W as your reference because, given the definition of the dB,
you'd need to divide by 0 which, as I'm sure you know, isn't acceptable.

--
73
Brian
www.g8osn.org.uk