[Elecraft] Measuring SSB RMS Power

[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 <john at kn5l.net> 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?