dBm, dBu, dBc?

Correct me where I am wrong, please.

dBm, decibel with reference of 1mW (at specified impedance)

dBu, decibel with reference of 1uV

What in God's name is dBc? This is in RF frequencies at 50 Ohm
impedance. I've seen it in a few service manuals, usually in relation
to harmonic levels. Please straighten me out, I would greatly
appreciate it.

Thanks,
Steve

 

No. That would be dBuV.

dBu is a voltage based measure used in ( pro ) audio where 0dBu is 0.775V.

Graham

 

http://www.google.com/search?hl=en&lr=&c2coff=1&oi=defmore&defl=en&q=define:dBc

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Regards,
Bob Monsen

A great truth is a truth whose opposite is also a great truth.
- Niels Bohr

 

Db relative to carrier power level.

John

 

Thank you everyone, it makes perfect sense now.

In response to dBu, dBuV.. I have a spectrum analyzer, an esa-1000,
and it uses dBu for all its measurements. Is this actually dBuV, just
abbreviated? Thanks again for the replies... Steve

 

It must be.

The dBu ( for audio ) was 'invented' in the mid 70s to replace the by then
misused dBm( 600 ohms) for voltage based measurements of audio signals..
Audio circuits had long ceased to use 'matched impedance working' for a host
of practical reasons.

The IEC defines decibel units. Most consist of dB+ reference level.

E.g....

dBV ( volts )

dBW ( watts)

dBm ( milliwatts ) ( + reference impedance ) - the W is inferred -
presumably for historical reasons

Graham

 

Makes sense. Thanks for the great replies!
Steve