"Glenn Booth" wrote in message
...
Crossposting removed.

Hi,

"don" wrote in message
...
dbm is as stated a reference of two like power values to a 1mW reference
however the impedence does not need to be 600 ohms, it can be any value
of
ohms as long as both power values are based on the same impedence

dbu is not unloaded but db(micro) it is as above but with a reference of
1microWatt it is not actually a u but the greek character mu

No, in this context it's dBu (note the capital B, for Bell). It's equally
valid to use a reference of 1 microWatt, but that's not what is used
commonly in professional audio. It might appear, for example, as
dB(?V/m) for electric field strength, relative to 1 microvolt per
metre. Not sure if the mu will come through in ASCII - apologies
if it doesn't.

If the load is 600 ohms, then dBu=dBm.

Regards,

Glenn.

Glenn is correct. dBu(micro)V is generally used for field strength
measurements and is referred to 1 microvolt/m.

dBu and dBm refer to the same *voltage* level, but different power levels.
dBm refers for 1mW into 600 ohms, dBu is the same voltage level (0.775v rms)
but without reference to a load. I have never heard of dBm being referred
to anything other than 1mW into 600 ohms, nor dBu being referred to 1 micro
watt. The point about dBu is that it is a *voltage* level reference, not a
power reference.

S.