Re: [Elecraft] Measuring SSB RMS Power

2019-06-21 Thread John Oppenheimer 
Searching email archives, found this comment from Lyle in KX3 list:

On 2/8/14 4:04 PM, Lyle Johnson wrote:
> The KX3 SSB compression algorithm is a bit different than the K3 for a
> number of reasons.  Reducing the bandwidth, removing the very low
> audio frequencies, etc., are all part of the algorithm design.

Therefore, simple power gain may not be the full story. Per above, power
is concentrated within a narrower BW as compression is increased.

Though I wonder if TXEQ with significant low frequency attenuation
changes compression power gain.

For testing, KX3 TX EQ is set to "KX3 Optimal" in:
https://www.kn5l.net/KX3-TxEq/

John KN5L

On 6/20/19 8:38 AM, John Oppenheimer wrote:
> Using DL1 with Oscilloscope to measure KX3 SSB RMS power:
> 
> https://www.kn5l.net/ssbpower/
> 
> Question, is this technique correct?
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Re: [Elecraft] Measuring SSB RMS Power

2019-06-20 Thread Fred Jensen 
Brown noise is supposed to be sleep inducing. The security folks used 
pink noise in the plenum above the SCIF's to mask conversations.  I 
can't remember exactly what the spectrum of A-weighting was, I think it 
had a dip in the mid-range.


The TV station I was employed by in college would "rent" us out to 
smaller AM and FM stations who didn't have a resident engineer. The 
standard AM configuration was an aggressive peak limiter followed by a 
"Sta-Level" with a very long time constant.  Result was the modulation 
was pegged at 99.5% all the time, and it sounded that way too ...  zero 
dynamic range.  Years ago, I looked at KFBK's waveform when the then new 
Rush Limbaugh was beginning his bloviation career.  It too was nearly 
constant since Rush could inhale very very quickly and talked very fast. 
[:-))


Non-classical FM stations [we serviced 4] used peak limiters only since 
100% FM modulation is an arbitrary number [75 KHz deviation then].  The 
one classical music FM station we had used no limiting/compression.  Our 
TV station used no limiter, NTSC aural deviation then was 25 KHz, 
however our two network feeds sounded fairly well compressed.


I seem to get best audio reports, and recordings a couple of folks have 
sent me sound best to me when my K3 compression reliably goes to 10 dB 
with occasional peaks to 15 dB on the bar graph.  Much more than that 
and there's clearly room noise in pauses and the audio begins to distort.


73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 6/20/2019 11:15 AM, Jim Brown wrote:
Bob is correct to the extent that Pink Noise approximates the SPECTRUM 
of speech, but John's is on target that speech is not continuous, but 
highly variable in amplitude. For uncompressed speech, the average 
value is typically as much as 20 dB below the peak value; compression 
can reduce that to 10 dB or less.  Highly sophisticated audio 
processing that has been used by radio broadcasters for at least 40 
years reduces that ratio to 6 dB or less. "If the modulation meter 
moves below 100%, it isn't loud enough!"


73, Jim K9YC

On 6/20/2019 10:13 AM, John Oppenheimer wrote:

Hi Bob,

Viewing pink noise with an oscilloscope, it is continuous, where as
speech has breaks.

The web page is evaluating both expected power to a load and compression
gain. Using a little over six second recorded speech. Recording contains
fast spoken words, mostly numbers and a few "this is a test" etc, for
maximum power over time. Evaluating scope shoot, about 25 words during
six second recording. Not even close to pink noise.

John KN5L

On 6/20/19 11:27 AM, Bob McGraw K4TAX wrote:
To evaluate speech use a pink noise source.  That is the standard 
source signal for acoustic measurements.


Bob, K4TAX


Sent from my iPhone


On Jun 20, 2019, at 10:34 AM, John Oppenheimer  wrote:

Hi Don,


On 6/20/19 9:21 AM, Don Wilhelm wrote:
John,

That connection is OK if you realize that your scope is reading 
the DC
voltage developed by rectifying the RF from 1/2 of the load.  You 
still

have to use the power formula that is in the DL1 manual.

Well yes, power references are DCV^2 / 25

DdB ratios computed using voltage ratios in the form of
20 * Log(v1/v2). For example, 0 compression Pep/Pav dB =
20 * log(15.3/5.24) = 9.3. I do need to flip the table title to 
Pav/Pep

for proper negative dB values, Done.

I prefer to allow the 'scope to read the full peak RF voltage.  
Connect
the 'scope probe to the side of one resistor which is connected to 
the

BNC jack (one of the leads closest to the BNC), and the 'scope ground
probe to one or the resistor leads furthermost away from from the 
BNC jack.

Using detected RF envelope for oscilloscope average RF measurement at
each digitized point during long, six second, trace. This will result
with increased accuracy when measuring modulated speech.

John KN5L


On 6/20/2019 9:38 AM, John Oppenheimer wrote:
Using DL1 with Oscilloscope to measure KX3 SSB RMS power:

https://www.kn5l.net/ssbpower/

Question, is this technique correct?

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Re: [Elecraft] Measuring SSB RMS Power

2019-06-20 Thread Jim Brown 
Bob is correct to the extent that Pink Noise approximates the SPECTRUM 
of speech, but John's is on target that speech is not continuous, but 
highly variable in amplitude. For uncompressed speech, the average value 
is typically as much as 20 dB below the peak value; compression can 
reduce that to 10 dB or less.  Highly sophisticated audio processing 
that has been used by radio broadcasters for at least 40 years reduces 
that ratio to 6 dB or less. "If the modulation meter moves below 100%, 
it isn't loud enough!"


73, Jim K9YC

On 6/20/2019 10:13 AM, John Oppenheimer wrote:

Hi Bob,

Viewing pink noise with an oscilloscope, it is continuous, where as
speech has breaks.

The web page is evaluating both expected power to a load and compression
gain. Using a little over six second recorded speech. Recording contains
fast spoken words, mostly numbers and a few "this is a test" etc, for
maximum power over time. Evaluating scope shoot, about 25 words during
six second recording. Not even close to pink noise.

John KN5L

On 6/20/19 11:27 AM, Bob McGraw K4TAX wrote:

To evaluate speech use a pink noise source.  That is the standard source signal 
for acoustic measurements.

Bob, K4TAX


Sent from my iPhone


On Jun 20, 2019, at 10:34 AM, John Oppenheimer  wrote:

Hi Don,


On 6/20/19 9:21 AM, Don Wilhelm wrote:
John,

That connection is OK if you realize that your scope is reading the DC
voltage developed by rectifying the RF from 1/2 of the load.  You still
have to use the power formula that is in the DL1 manual.

Well yes, power references are DCV^2 / 25

DdB ratios computed using voltage ratios in the form of
20 * Log(v1/v2). For example, 0 compression Pep/Pav dB =
20 * log(15.3/5.24) = 9.3. I do need to flip the table title to Pav/Pep
for proper negative dB values, Done.


I prefer to allow the 'scope to read the full peak RF voltage.  Connect
the 'scope probe to the side of one resistor which is connected to the
BNC jack (one of the leads closest to the BNC), and the 'scope ground
probe to one or the resistor leads furthermost away from from the BNC jack.

Using detected RF envelope for oscilloscope average RF measurement at
each digitized point during long, six second, trace. This will result
with increased accuracy when measuring modulated speech.

John KN5L


On 6/20/2019 9:38 AM, John Oppenheimer wrote:
Using DL1 with Oscilloscope to measure KX3 SSB RMS power:

https://www.kn5l.net/ssbpower/

Question, is this technique correct?

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Re: [Elecraft] Measuring SSB RMS Power

2019-06-20 Thread John Oppenheimer 
Hi Bob,

Viewing pink noise with an oscilloscope, it is continuous, where as
speech has breaks.

The web page is evaluating both expected power to a load and compression
gain. Using a little over six second recorded speech. Recording contains
fast spoken words, mostly numbers and a few "this is a test" etc, for
maximum power over time. Evaluating scope shoot, about 25 words during
six second recording. Not even close to pink noise.

John KN5L

On 6/20/19 11:27 AM, Bob McGraw K4TAX wrote:
> To evaluate speech use a pink noise source.  That is the standard source 
> signal for acoustic measurements. 
> 
> Bob, K4TAX
> 
> 
> Sent from my iPhone
> 
>> On Jun 20, 2019, at 10:34 AM, John Oppenheimer  wrote:
>>
>> Hi Don,
>>
>>> On 6/20/19 9:21 AM, Don Wilhelm wrote:
>>> John,
>>>
>>> That connection is OK if you realize that your scope is reading the DC 
>>> voltage developed by rectifying the RF from 1/2 of the load.  You still 
>>> have to use the power formula that is in the DL1 manual.
>>
>> Well yes, power references are DCV^2 / 25
>>
>> DdB ratios computed using voltage ratios in the form of
>> 20 * Log(v1/v2). For example, 0 compression Pep/Pav dB =
>> 20 * log(15.3/5.24) = 9.3. I do need to flip the table title to Pav/Pep
>> for proper negative dB values, Done.
>>
>>> I prefer to allow the 'scope to read the full peak RF voltage.  Connect 
>>> the 'scope probe to the side of one resistor which is connected to the 
>>> BNC jack (one of the leads closest to the BNC), and the 'scope ground 
>>> probe to one or the resistor leads furthermost away from from the BNC jack.
>>
>> Using detected RF envelope for oscilloscope average RF measurement at
>> each digitized point during long, six second, trace. This will result
>> with increased accuracy when measuring modulated speech.
>>
>> John KN5L
>>
 On 6/20/2019 9:38 AM, John Oppenheimer wrote:
 Using DL1 with Oscilloscope to measure KX3 SSB RMS power:

 https://www.kn5l.net/ssbpower/

 Question, is this technique correct?
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Re: [Elecraft] Measuring SSB RMS Power

2019-06-20 Thread Bob McGraw K4TAX 
To evaluate speech use a pink noise source.  That is the standard source signal 
for acoustic measurements. 

Bob, K4TAX


Sent from my iPhone

> On Jun 20, 2019, at 10:34 AM, John Oppenheimer  wrote:
> 
> Hi Don,
> 
>> On 6/20/19 9:21 AM, Don Wilhelm wrote:
>> John,
>> 
>> That connection is OK if you realize that your scope is reading the DC 
>> voltage developed by rectifying the RF from 1/2 of the load.  You still 
>> have to use the power formula that is in the DL1 manual.
> 
> Well yes, power references are DCV^2 / 25
> 
> DdB ratios computed using voltage ratios in the form of
> 20 * Log(v1/v2). For example, 0 compression Pep/Pav dB =
> 20 * log(15.3/5.24) = 9.3. I do need to flip the table title to Pav/Pep
> for proper negative dB values, Done.
> 
>> I prefer to allow the 'scope to read the full peak RF voltage.  Connect 
>> the 'scope probe to the side of one resistor which is connected to the 
>> BNC jack (one of the leads closest to the BNC), and the 'scope ground 
>> probe to one or the resistor leads furthermost away from from the BNC jack.
> 
> Using detected RF envelope for oscilloscope average RF measurement at
> each digitized point during long, six second, trace. This will result
> with increased accuracy when measuring modulated speech.
> 
> John KN5L
> 
>>> On 6/20/2019 9:38 AM, John Oppenheimer wrote:
>>> Using DL1 with Oscilloscope to measure KX3 SSB RMS power:
>>> 
>>> https://www.kn5l.net/ssbpower/
>>> 
>>> Question, is this technique correct?
>>> 
>> 
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Re: [Elecraft] Measuring SSB RMS Power

2019-06-20 Thread John Oppenheimer 
Hi Bob,

Document Table 1, Line 7. speech = V/5*2^.5. which is same as Vrms/5.
Using measured RMS ratios, Vrms=15.3, 15.3/5 = 3V, compared to measured
5.24V.

Speech is rather undefined, so not too worried about the discrepancy. My
speech with no pauses is ~= Vrms / 3.

Really what is being evaluated is gain resulting from speech compression.

John KN5L


On 6/20/19 9:29 AM, Bob McGraw K4TAX wrote:
> Here is a paper on the topic. This covers the correct procedure. 
> 
> http://www.eng.auburn.edu/~troppel/courses/TIMS-manuals-r5/TIMS%20Experiment%20Manuals/Student_Text/Vol-A1/a1-12.pdf
> 
> 
> 73
> 
> Bob, K4TAX
> 
> 
> Sent from my iPhone
> 
> On Jun 20, 2019, at 8:38 AM, John Oppenheimer  > wrote:
> 
>> Using DL1 with Oscilloscope to measure KX3 SSB RMS power:
>>
>> https://www.kn5l.net/ssbpower/
>>
>> Question, is this technique correct?
>>
>> John KN5L
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Re: [Elecraft] Measuring SSB RMS Power

2019-06-20 Thread John Oppenheimer 
Hi Don,

On 6/20/19 9:21 AM, Don Wilhelm wrote:
> John,
> 
> That connection is OK if you realize that your scope is reading the DC 
> voltage developed by rectifying the RF from 1/2 of the load.  You still 
> have to use the power formula that is in the DL1 manual.

Well yes, power references are DCV^2 / 25

DdB ratios computed using voltage ratios in the form of
20 * Log(v1/v2). For example, 0 compression Pep/Pav dB =
20 * log(15.3/5.24) = 9.3. I do need to flip the table title to Pav/Pep
for proper negative dB values, Done.

> I prefer to allow the 'scope to read the full peak RF voltage.  Connect 
> the 'scope probe to the side of one resistor which is connected to the 
> BNC jack (one of the leads closest to the BNC), and the 'scope ground 
> probe to one or the resistor leads furthermost away from from the BNC jack.

Using detected RF envelope for oscilloscope average RF measurement at
each digitized point during long, six second, trace. This will result
with increased accuracy when measuring modulated speech.

John KN5L

> On 6/20/2019 9:38 AM, John Oppenheimer wrote:
>> Using DL1 with Oscilloscope to measure KX3 SSB RMS power:
>>
>> https://www.kn5l.net/ssbpower/
>>
>> Question, is this technique correct?
>>
>
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Re: [Elecraft] Measuring SSB RMS Power

2019-06-20 Thread Don Wilhelm 

Ken,

The DL1 is a 50 ohm load.  I did specify that the formula was applicable 
for a 50 ohm load.


For other loads, the formula is Vpeak squared divided by 8R.

It saves the trouble of converting to RMS and then using the more 
familiar Vrms squared divided by R.


If you wish to derive the formula yourself, you can do that, but 
represent the RMS voltage as V time sqrt 2 rather then the approximation 
of 1.414 (or 0.707) which is normally shown.  The sqrt will cancel out 
when it is squared.


73,
Don W3FPR

On 6/20/2019 10:50 AM, Ken Roberson via Elecraft wrote:

  Don , That may be peak to peak voltage squared decided by 400 for a 50 ohm 
load.
Thanks 73 Ken K5DNL

 On Thursday, June 20, 2019, 9:30:46 AM CDT, Bob McGraw K4TAX 
 wrote:
  
  Here is a paper on the topic. This covers the correct procedure.


http://www.eng.auburn.edu/~troppel/courses/TIMS-manuals-r5/TIMS%20Experiment%20Manuals/Student_Text/Vol-A1/a1-12.pdf

73
Bob, K4TAX


Sent from my iPhone


On Jun 20, 2019, at 8:38 AM, John Oppenheimer  wrote:

Using DL1 with Oscilloscope to measure KX3 SSB RMS power:

https://www.kn5l.net/ssbpower/

Question, is this technique correct?

John KN5L
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Re: [Elecraft] Measuring SSB RMS Power

2019-06-20 Thread Ken Roberson via Elecraft 
 Don , That may be peak to peak voltage squared decided by 400 for a 50 ohm 
load.
Thanks 73 Ken K5DNL

On Thursday, June 20, 2019, 9:30:46 AM CDT, Bob McGraw K4TAX 
 wrote:  
 
 Here is a paper on the topic. This covers the correct procedure. 

http://www.eng.auburn.edu/~troppel/courses/TIMS-manuals-r5/TIMS%20Experiment%20Manuals/Student_Text/Vol-A1/a1-12.pdf

73
Bob, K4TAX


Sent from my iPhone

> On Jun 20, 2019, at 8:38 AM, John Oppenheimer  wrote:
> 
> Using DL1 with Oscilloscope to measure KX3 SSB RMS power:
> 
> https://www.kn5l.net/ssbpower/
> 
> Question, is this technique correct?
> 
> John KN5L
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Re: [Elecraft] Measuring SSB RMS Power

2019-06-20 Thread Bob McGraw K4TAX 
Here is a paper on the topic. This covers the correct procedure. 

http://www.eng.auburn.edu/~troppel/courses/TIMS-manuals-r5/TIMS%20Experiment%20Manuals/Student_Text/Vol-A1/a1-12.pdf

73
Bob, K4TAX


Sent from my iPhone

> On Jun 20, 2019, at 8:38 AM, John Oppenheimer  wrote:
> 
> Using DL1 with Oscilloscope to measure KX3 SSB RMS power:
> 
> https://www.kn5l.net/ssbpower/
> 
> Question, is this technique correct?
> 
> John KN5L
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Re: [Elecraft] Measuring SSB RMS Power

2019-06-20 Thread Don Wilhelm 

John,

That connection is OK if you realize that your scope is reading the DC 
voltage developed by rectifying the RF from 1/2 of the load.  You still 
have to use the power formula that is in the DL1 manual.


I prefer to allow the 'scope to read the full peak RF voltage.  Connect 
the 'scope probe to the side of one resistor which is connected to the 
BNC jack (one of the leads closest to the BNC), and the 'scope ground 
probe to one or the resistor leads furthermost away from from the BNC jack.


Then use the formula to convert peak voltage to power (for a 50 ohm 
load) which is V squared then divided by 400.  Easy to do quickly with a 
handy calculator.


73,
Don W3FPR

On 6/20/2019 9:38 AM, John Oppenheimer wrote:

Using DL1 with Oscilloscope to measure KX3 SSB RMS power:

https://www.kn5l.net/ssbpower/

Question, is this technique correct?


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