Confusing wording?

C

Cursitor Doom

Guest
Gentlemen,

I came across this instruction in a service manual and for some reason
find it hard to understand its meaning. It's probably my fault, but
I'd appreciate confirmation of that. :)

The wording is:

13. "Adjust output dBm until the power meter indicates +9dBm.
14. "Adjust tuning slowly through the range 100kHz to 3Ghz and note
the meter readings at 25Mhz intervals. The difference between the
readings should not be greater than 1.0dB."

Are they trying to say all the readings should lie between 7.74dBw and
10.26dBw?? It's far from clear - to me at any rate!

Thanks,

CD
 
On 7/02/2020 6:31 am, Cursitor Doom wrote:
Gentlemen,

I came across this instruction in a service manual and for some reason
find it hard to understand its meaning. It's probably my fault, but
I'd appreciate confirmation of that. :)

The wording is:

13. "Adjust output dBm until the power meter indicates +9dBm.
14. "Adjust tuning slowly through the range 100kHz to 3Ghz and note
the meter readings at 25Mhz intervals. The difference between the
readings should not be greater than 1.0dB."

Are they trying to say all the readings should lie between 7.74dBw and
10.26dBw?? It's far from clear - to me at any rate!

Thanks,

CD
Click to expand...

I would take it to mean the taken readings should not be above or below
each other than 1db.
 
On Fri, 7 Feb 2020 07:41:04 +0800, RheillyPhoull
<Rheilly@bigslong.com> wrote:


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

That wording's even worse than the original!
 
On 2020-02-06, Cursitor Doom <curd@notformail.com> wrote:
Gentlemen,

I came across this instruction in a service manual and for some reason
find it hard to understand its meaning. It's probably my fault, but
I'd appreciate confirmation of that. :)

The wording is:

13. "Adjust output dBm until the power meter indicates +9dBm.
14. "Adjust tuning slowly through the range 100kHz to 3Ghz and note
the meter readings at 25Mhz intervals. The difference between the
readings should not be greater than 1.0dB."

Are they trying to say all the readings should lie between 7.74dBw and
10.26dBw?? It's far from clear - to me at any rate!
Click to expand...

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.
 
Cursitor Doom <curd@notformail.com> writes:

Gentlemen,

I came across this instruction in a service manual and for some reason
find it hard to understand its meaning. It's probably my fault, but
I'd appreciate confirmation of that. :)

The wording is:

13. "Adjust output dBm until the power meter indicates +9dBm.
14. "Adjust tuning slowly through the range 100kHz to 3Ghz and note
the meter readings at 25Mhz intervals. The difference between the
readings should not be greater than 1.0dB."

Are they trying to say all the readings should lie between 7.74dBw and
10.26dBw?? It's far from clear - to me at any rate!
Click to expand...

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
 
On Fri, 07 Feb 2020 08:45:24 +0200, Mikko OH2HVJ
<mikko.syrjalahti@nospam.fi> wrote:

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 ?
Click to expand...

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.
 
On Thu, 06 Feb 2020 22:31:30 +0000, Cursitor Doom
<curd@notformail.com> wrote:

Are they trying to say all the readings should lie between 7.74dBw and
10.26dBw?? It's far from clear - to me at any rate!
Click to expand...

Not by my reckoning. Should be 7.98 and 9.77dBw.
 
Martin James Smith wrote:
On Thu, 06 Feb 2020 22:31:30 +0000, Cursitor Doom
curd@notformail.com> wrote:

Are they trying to say all the readings should lie between 7.74dBw and
10.26dBw?? It's far from clear - to me at any rate!

Not by my reckoning. Should be 7.98 and 9.77dBw.
Click to expand...

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
 
On Fri, 07 Feb 2020 16:31:33 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:

Martin James Smith wrote:
On Thu, 06 Feb 2020 22:31:30 +0000, Cursitor Doom
curd@notformail.com> wrote:

Are they trying to say all the readings should lie between 7.74dBw and
10.26dBw?? It's far from clear - to me at any rate!

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.
Click to expand...

Argh, you're right! Yes, I should have written dBm. WTF did I get
"dBw" from?? I don't even know myself. :/
 
On Fri, 07 Feb 2020 14:07:12 +0000, Martin James Smith
<marty889@freeserve.net> wrote:

On Thu, 06 Feb 2020 22:31:30 +0000, Cursitor Doom
curd@notformail.com> wrote:

Are they trying to say all the readings should lie between 7.74dBw and
10.26dBw?? It's far from clear - to me at any rate!

Not by my reckoning. Should be 7.98 and 9.77dBw.
Click to expand...

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....
 
On Sat, 08 Feb 2020 17:11:34 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:

On 2020-02-07 18:05, Cursitor Doom wrote:

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.

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

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
 
On 2020-02-07 18:05, Cursitor Doom wrote:
On Fri, 07 Feb 2020 14:07:12 +0000, Martin James Smith
marty889@freeserve.net> wrote:

On Thu, 06 Feb 2020 22:31:30 +0000, Cursitor Doom
curd@notformail.com> wrote:

Are they trying to say all the readings should lie between 7.74dBw and
10.26dBw?? It's far from clear - to me at any rate!

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

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.
Click to expand...

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

Jeroen Belleman
 
Cursitor Doom <curd@notformail.com> writes:

On Sat, 08 Feb 2020 17:11:34 +0100, Jeroen Belleman

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

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
Click to expand...

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
 
On 08/02/20 16:26, Cursitor Doom wrote:
On Sat, 08 Feb 2020 17:11:34 +0100, Jeroen Belleman
jeroen@nospam.please> wrote:

On 2020-02-07 18:05, Cursitor Doom wrote:

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.

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

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
Click to expand...

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 https://www.google.com/search?q=dBm+to+power
but I doubt you will since you have killfiled me :)
 
On Saturday, February 8, 2020 at 11:26:51 AM UTC-5, Cursitor Doom wrote:
On Sat, 08 Feb 2020 17:11:34 +0100, Jeroen Belleman
jeroen@nospam.please> wrote:

On 2020-02-07 18:05, Cursitor Doom wrote:

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.

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

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
Click to expand...

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

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209
 
On 08/02/20 18:19, Rick C wrote:
On Saturday, February 8, 2020 at 11:26:51 AM UTC-5, Cursitor Doom wrote:
On Sat, 08 Feb 2020 17:11:34 +0100, Jeroen Belleman
jeroen@nospam.please> wrote:

On 2020-02-07 18:05, Cursitor Doom wrote:

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.

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

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

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

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.
 
On Sat, 08 Feb 2020 19:17:55 +0200, Mikko OH2HVJ
<mikko.syrjalahti@nospam.fi> wrote:

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

Agreed.

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.
Click to expand...

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

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

Which differs from your own answer further up the thread! And I have
no idea what you mean by "combine" either.
 
On 2/8/2020 5:58 PM, amdx wrote:
On 2/6/2020 4:31 PM, Cursitor Doom wrote:
Gentlemen,

I came across this instruction in a service manual and for some reason
find it hard to understand its meaning. It's probably my fault, but
I'd appreciate confirmation of that. :)

The wording is:

13.  "Adjust output dBm until the power meter indicates +9dBm.
14.  "Adjust tuning slowly through the range 100kHz to 3Ghz and note
the meter readings at 25Mhz intervals. The difference between the
readings should not be greater than 1.0dB."

Are they trying to say all the readings should lie between 7.74dBw and
10.26dBw?? It's far from clear - to me at any rate!

Thanks,

CD

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
Click to expand...

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
 
On 2/6/2020 4:31 PM, Cursitor Doom wrote:
Gentlemen,

I came across this instruction in a service manual and for some reason
find it hard to understand its meaning. It's probably my fault, but
I'd appreciate confirmation of that. :)

The wording is:

13. "Adjust output dBm until the power meter indicates +9dBm.
14. "Adjust tuning slowly through the range 100kHz to 3Ghz and note
the meter readings at 25Mhz intervals. The difference between the
readings should not be greater than 1.0dB."

Are they trying to say all the readings should lie between 7.74dBw and
10.26dBw?? It's far from clear - to me at any rate!

Thanks,

CD

I see it as,
Click to expand...

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
 
Cursitor Doom <curd@notformail.com> writes:

On Sat, 08 Feb 2020 19:17:55 +0200, Mikko OH2HVJ
But if you combine 9dBm and 1dBm, you get 8mW+1mW=9mW=9.6dBm.

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

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
 
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