decibel and logarithmic scales

Hi

Could you please help me with these queries? Thanks.

Regards
PG

Q1
I hesitate to call the decibel a "unit" in the same way that a Volt or a Farad is a "unit".
A decibel is a ratio. It only becomes a unit when given a modifier such as dBm.
dBm is a power relative to 1 milli-watt, so 1 Watt can be expressed as +30dBm.

Which leads on to the concept of larger or smaller.

10dB = 1Bel

So the dB is less than the B.
I think you have blown your own mind on this one!

Q2
I cannot see where the 0.5 comes from.
I think that the author has had a moment of confusion, possibly he was thinking about V being the peak voltage as you may measure with an oscilloscope.

JimB

Thank you, Jim.

I'm still confused about Q1.

Regards
PG

hi PG,

Consider the prefix's used for length measurement units.

1metre= 100centi-metres= 1000milli-metres

1Bel =10 deci-Bel

The conventions used are the same throughout most of the engineering values

E

Thanks Jim for the heads up on my typo.

Thank you, Eric.

I do know that what those prefixes mean. But the way that text puts it is not very clear and that was the reason I reached this wrong conclusion which I mentioned in my previous post.

Regards
PG

Consider this: 10 pennies equal a dime, but (number of dimes)x10 = number of pennies needed to equal that amount in value.

It is all in how the question is asked.
John