dBm, dBu, dBc?

[sck0006]

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

 

[Pooh Bear]

Correct me where I am wrong, please.

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

dBu, decibel with reference of 1uV

No. That would be dBuV.

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

Graham

 

[Bob Monsen]

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.

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

---
Regards,
Bob Monsen

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

 

[John Larkin]

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

Db relative to carrier power level.

John

 

[sck0006]

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

 

[Pooh Bear]

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?

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

 

[sck0006]

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