Confusing wording?

I would take it to mean the taken readings should not be above or below each other than 1db.

That wording's even worse than the original!

I'm guessing they mean difference between consecutive readings, but they may mean difference between any two readings (ie between max and min)

100kHz really? 100MHz perhaps?

--
  Jasen.

Signal generator output flatness test ? All measurements should be inside 1dB. If you start with 9.0dBm output, maximum is 9.4 and minimum

8.4, that's a pass. If a single measurement is 8.3, it's a fail.

What's the box you're servicing ?

--
mikko

Agilent 8752C. But I'm not servicing it. I'm not qualified to service this kind of stuff. I do recommission them rather than see them go to landfill, though, but that's another story. Thanks for the reply.

Not by my reckoning. Should be 7.98 and 9.77dBw.

What the *** is a dBw? And how did you get those values?

To me, the original wording simply means that max-min < 1dB, where both max and min are the values in dBm. There is really no way to tell what max and min should be, except that they bracket this 9dBm value.

Jeroen Belleman

Argh, you're right! Yes, I should have written dBm. WTF did I get "dBw" from?? I don't even know myself. :/

I've taken another look at it and come up with something else entirely. I'll show my working for the avoidance of doubt:

Q: What is 9dBm + 1.0dB?

1. Convert 9dBm to Watts using lookup tables = 8mW approx.
2. What, then, is 8mW + 1.0dB?
3. 1dB translates to a factor of 1.259 according to the tables.
4. Multiply 0.008 by 1.259 = 0.01W or 10mW.
5. Use the tables to convert 10mW back into dBm = 10dBm.

So the permissible upper limit for a 9dBm signal is 10dBm. You can use the same method to find the lower limit (9dBm-1.0dB). I think that's correct, anyway, although since this is not my field, I could possibly be wrong....

Something should catch your eye here: 9dBm + 1dB = 10dBm. Simple. That's what the dB was invented for.

Jeroen Belleman

I'm afraid that makes no sense to me whatsoever, so I'll have to continue with my cumbersome methodology! If it had been 9dBm + 1dBm =

10dBm I could see your point. Looks like you missed out a "m". :-D

No, unsurprisingly he didn't.

dB is relative power a.k.a. a ratio, log scale dBm is absolute power

9dBm = 7.94mW 1dBm = 1mW 7.94mW + 1mW = 8.94mW = 9.51dBm != 10dBm

FFI, see

but I doubt you will since you have killfiled me :)

Nope, it works exactly like that. 1dB is relation (multiply) and 1dBm is absolute power.

If you increase power from 9dBm by 1dB, that equals 10^(0.1)=1.25 multiplication, i.e. 9dBm + 1dB = 8mW * 1.25 = 10mW = 10dBm.

But if you combine 9dBm and 1dBm, you get 8mW+1mW=9mW=9.6dBm.

--
mikko

That just shows you don't understand dB in any way.

--

  Rick C. 

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And can't be bothered to - do /trivial/ research - try to understand the simple facts he should have uncovered

That's repeated behaviour for him.

Agreed.

Agreed. But that's just the "cumbersome method" I used myself earlier up the thread.

Which differs from your own answer further up the thread! And I have no idea what you mean by "combine" either.

I see it as,

The spread between you highest and your lowest measurement should not have more than 1db difference. It could be a lowest reading of 8.5db and highest of 9.5db or a low of

8db and high of 9db or a low of 9db and a high of 10db.

But I don't even know what you are working on.

Mikek

OK, add m to all those db.

It could be a lowest reading of 8.5dbm and highest of 9.5dbm or a low of 8dbm and high of 9dbm or a low of 9dbm and a high of 10dbm.

Mikek

Nope. There I wrote +1dB, not +1dBm.

+1dB corresponds to relative increase of roughly +25%. +1dBm correspods to absolute increase of 1mW.

Google for 'ARRL tutorial for Decibel' and read it, that might explain.

But for your purposes, just check my first message to get pass/fail result.

--
mikko