A Complex Metaphysical Conundrum

I can just imagine you all furiously Googling for the answer right now...

:-D

Very brave, John! I think the lack of response thus far indicates how terrified the great and the good here are of getting it wrong, 'cos those at the top have the farthest to fall in terms of reputation. I'll provide the answer the same time tomorrow and we'll see if there's any other brave souls out there. ;-)

Changing a signal level can be thought of as multiplying the signal by a constant. That constant can't have units because then you'd have (dBmV)^2

So that answer is likely to be that the increase is by 2 dB not 2 dBmV

If I have a meter that shows dBmV, and it says 3 and I crank up the input so it says 5, it went up by 2.

Do you have a counter-case? 3+2 equals something that's not 5?

You can change something by adding, too.

I haven't looked at it in detail but a bit of playing with a search engine finds the question here:

It says that a signal level can never go from 3 dBmV to 5 dBmV. I think it can.

This is a silly word game.

Haven't we had a discussion about this already some four years ago? Weren't you Don Kuenz then?

Jeroen Belleman

I'm sure I could find someone teaching mathematics like that in our wonderful modern school system in no time at all LOL.

I don't recall any such discussion and no, I'm not Don Kuenz either.

Jeez, when I said, "No Googling" I didn't seriously think anyone here would be dumb enough to need to actually do so! :-D From the site you pointed to: "This kind of statement is incorrect, because signal levels cannot increase or decrease in increments of dBmV, only dB." Well you learn something new every day on the net, doncha? ;->

How about this for an exam question.

Give an example of the construction of a 6dB power splitter, for use in a 50 ohm system, using only resistors. Assume that the resistors do not have any frequency dependent characteristcs at any frequency of use. There is no need to calculate any resistor values.

What happens to the other half of the power going into the 6 dB splitter when it is delivering one quarter of the input power through each output?

Why is it not possible to make a 3 dB power splitter using only resistors?

Or this.

Draw an op amp with the + input grounded using two 1K ohm resistors in an inverting conviguration. The op amp is shown with +12V and -12V power rails. Connect the input of this circuit to the centre of two 2K ohm resistors as a potential divider between +12V and 0V (ground) Ask what will be on the op amp's output when measured with a high impedance voltmeter.

If + is a boolean Or operator then perhaps 3 + 2 = 3

I don't see any mention of any search engine in your first post.

I tend to agree with John Larkin on this.

If a student can use a meter to see that a signal which was 3 somethings is now 5 somethings (depending on what is being measured) then I give them a pass.

So going back to the orginal question as stated, you're saying the statement in quotes is *correct* then. Nice to have a straight answer.

If you mean that do I think that something increases by 2 when it goes from

You can also multiply it by 5/3 to get the same effect if you want. I don't mind.

db is a logarythmic ratio. an increase from +3dBmV to +5dBmV is an increase by 2dB (not 2dBmV)

Adding 2dBmV to +3dBmV will not get you +5dBmV because it's a logarythmic scale.

Allright then. The statement is wrong. An increase is in dB, not in dBmV.

Jeroen Belleman