[Boatanchors] TURBO RANGER FS

[Bry Carling]

Thanks for the detailed explanation, Mike.

I had never heard it discussed that way before. IN terms of my 
experience with audio engineering, we always just used an HP 
distortion meter to analyze the distortion and tried to make sure 
THAT was kept within our specifications.

I never examined the components of the distortion, such as 
phase etc. since there were other parameters you could 
adjust to affect the overall % dist. such as bias settings etc.

Call me an "Empirical Engineer", but in the pragmatic world 
of technical adjustments in which I functioned, it usually meant 
that we tweaked a few things for minimum meter deflection on 
the HP meter sitting on the bench!

> Hello from a now retired career broadcast engineer who has spent waaaaay too
> much time trying to please programming folks with audio processing -- you
> know, louder, clearer, jump-out-of-the-dial, beat the competitors audio.
> 
> Phase linear bandwidth limiting is, in fact, very real.
> 
> Envision this.
> 
> When we clip audio, we create square (perhaps more accurately, squared-off)
> waves.  Square waves have the greatest possible average/RMS power in the
> wave of any waveform short of pure DC.  Square waves are essentially
> switched DC!
> 
> But -- if the audio circuitry following the clipping and the generation of
> the square waves isn't "phase linear" -- and indeed, frequency-response
> linear as well all the way down to DC -- the steep vertical beginning and
> endings of each pulse/square wave will become bent, as will the flat top.
> Worse, for folks trying to be loud, overshoot and possible ringing will
> create peaks that extend above the flat tops of the square waves.  Since
> modulation percentage is figured on the peak value of positive and the
> negative going modulation, and should never exceed 100% negative, two things
> are extremely important!  Do not distort the square waves which phase
> anomalies, among other flaws, will do, and always try to have the
> positive-going peaks stronger than the negative-going peaks. And any of
> those little peaks that stick up above the flat top of the square wave will
> reduce the average/RMS power in the audio signal relative to the peak value
> of the wave.
> 
> By the way, originally, AM broadcast rules did not limit positive-going
> modulation percentage -- just negative-going ones.  As a result, many
> broadcast engineers (myself included) used unbalanced push-pull amplifiers,
> negative-cycle loading, asymmetric clippers, and the like, resulting, in
> some cases, positive-going modulation peaks reaching 200% while holding
> negative-going modulation peaks to 100%.  Some years ago the FCC decided
> this was going to have to stop, and mandated positive peaks not to exceed
> 125% modulation.  Took the fun right out of it!
> 
> Anyway, that the romance many of us felt for broadcast and shortwave AM when
> we were kids seems a harmless, if expensive, corner of our Amateur radio
> service and hobby!
> 
> Note: average and RMS are similar, but not exactly the same.  Either term
> works for this discussion.
> 
> So dust of those old Volumax, Audimax, CRL processors, Optimods, and the
> like, and let the hi-fi roll on!
> 
> 73 all !
> 
> Mike/
> K5MGR
> __________________
> 
> 
> -----Original Message-----
> From: Boat Anchor Owners and Collectors List
> [mailto:BOATANCHORS at LISTSERV.TEMPE.GOV]On Behalf Of Bry Carling
> Sent: Thursday, March 13, 2008 6:10 AM
> To: BOATANCHORS at LISTSERV.TEMPE.GOV
> Subject: Re: [Boatanchors] TURBO RANGER FS
> 
> 
> de Nigel Holmes <Holmes.Nigel at ABC.NET.AU>
> > phase linear bandwidth limiting
> 
> Now THERE Is a five dollar term if ever I heard one!
> 
> How do you do bandwidth limiting that isn't "phase linear?
> What does it sound like?
> 
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