What's a dBu ?
 

On Mon, 7 Nov 2005 20:25:50 -0000, "Jeff" wrote:

Mmmmm..... I reckon it's just you. ;-)

d

Pearce Consulting
http://www.pearce.uk.com

Then try doing a little research on the web then, you will find at least
four usages of "dBu".

The correct one,

dB rel 1 micro volt, when written without access to mu,

dB rel 1 micro volt/m (used by the FCC)

and dB rel 1 micro Watt (mainly sat downlink people).

Regards
Jeff


A plague on all their houses! The FCC at least should know better.

d

Pearce Consulting
http://www.pearce.uk.com

What's a dBu ?
 

On Mon, 7 Nov 2005 15:41:48 -0000, "Jeff" wrote:


"
Should be relative to a microvolt into a 600 Ohm load.

Forget microVolt!
0 dBu is steady AF established at 775 milliVolts line level -- regardless
of load Z.

It is an easy mistake to make, because dB relative to a microvolt is often
written as dBu rather than
using the Greek letter 'mu'; a limitation of the ASCII character set!!

That wasn't the mistake - the mistake was to think that it ever had
anything to do with the Greek alphabet! The 'u' in dBu stands for
unterminated or unloaded, because, while it is the same voltage as
that required to maintain a power level of 1 milliwatt (not micro)
into a 600 ohm load, it's a *voltage* measure, not a power measure.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

What's a dBu ?
 

On Mon, 7 Nov 2005 19:39:02 -0000, "Jeff" wrote:


It is an easy mistake to make, because dB relative to a microvolt is often
written as dBu rather than
using the Greek letter 'mu'; a limitation of the ASCII character set!!

Jeff


dB relative to a microvolt is written as dBuV, so there need be no
confusion.


Well I am afraid that RF engineers are a lazy breed and it is often written
as dBu, much in the same way as dBm.

That's not lazy, that's efficient! That's what engineers *do*..... :-)
--

Stewart Pinkerton | Music is Art - Audio is Engineering

What's a dBu ?
 

On Mon, 07 Nov 2005 19:56:45 GMT, (Don Pearce)
wrote:

On Mon, 7 Nov 2005 19:39:02 -0000, "Jeff" wrote:


It is an easy mistake to make, because dB relative to a microvolt is often
written as dBu rather than
using the Greek letter 'mu'; a limitation of the ASCII character set!!

Jeff


dB relative to a microvolt is written as dBuV, so there need be no
confusion.


Well I am afraid that RF engineers are a lazy breed and it is often written
as dBu, much in the same way as dBm.

Jeff


Well, I've been an RF engineer all my life, and I've never come across
dBu instead of dBuV.

I can't match Don's experienec of RF engineering as a toddler, but I
spent 30 years in the C&I industry, and I've heard about every
possible abbreviation. However, I agree that you always see dBuV fully
written out, because it is absolutely *not* the same measure as dBu,
especially since RF terminology generally relates to 50 ohm loads.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

What's a dBu ?
 

On Mon, 7 Nov 2005 20:25:50 -0000, "Jeff" wrote:

Mmmmm..... I reckon it's just you. ;-)

d

Pearce Consulting
http://www.pearce.uk.com

Then try doing a little research on the web then, you will find at least
four usages of "dBu".

The correct one,

dB rel 1 micro volt, when written without access to mu,

dB rel 1 micro volt/m (used by the FCC)

and dB rel 1 micro Watt (mainly sat downlink people).

Hmmmmm, you're right. Tsk, tsk..............

Could be interesting if you try to shove +10dBu down a system which
was expecting +10dBuV........................
--

Stewart Pinkerton | Music is Art - Audio is Engineering