[Elecraft] P3 SVGA - measuring occupied bandwidth

[Jim Brown]

On 5/23/2018 12:54 AM, Richard Lamont wrote:
> Jim - in this context, are you using the definition of "occupied
> bandwidth" as in ITU RR 1.153, i.e. 99% mean power? If so, how do you do
> that with the P3 SVGA?

For CW, I transmit a long series of dits, put the P3 in peak mode, and 
accumulate peaks. When the display stops changing, I freeze it, use the 
cursor to manually log enough points to define the curve on both sides 
of the carrier, starting at -20dB carrier and every 5 dB until the data 
falls off screen. I then save the screen to a file.

I've done essentially the same thing with RTTY and PSK.  For SSB, my 
test signal is bandwidth limited Pink Noise. Pink Noise is widely used 
as an audio test signal because both spectral balance and dynamics are a 
good first approximation of speech. Pink Noise is defined as equal power 
per percentage bandwidth, whereas white noise is equal voltage per Hz. 
Pink noise can be though of as white noise with a 3dB per octave 
rolloff. That's not easy to generate -- an RC rolloff is 6 dB/octave.

And this important comment. NC0B uses White Noise as a source. This is 
VERY BAD practice, because it puts nearly all of the modulation above 
the voice spectrum, and greatly de-emphasizes speech. I've corrected him 
on this three times, first as long as five years ago, yet he continues 
to do it wrong. The importance of this is that GOOD audio processing is 
designed for the spectrum and dynamics of speech, so any audio test 
signal should approximate speech as closely as possible. Rob is a great 
engineer and does ham radio a great service with his testing, but he 
fails to even attempt to understand the difference between RF and audio.

As to my credentials to say this -- I spent 40 years in pro audio, with 
much of my work directed to sound systems for both speech 
intelligibility and music. For 20 years, I've been a member of the AES 
Standards Committee, and of Working Groups on Speech Intellibility. 
About ten years ago, I was elected a Fellow of the AES.

73, Jim K9YC