[AMRadio] re: Apache audio not good

[russ dworakowski]

Yes,  you  can  leave  the clipper  in place,  But  it still distorts
the  audio  down  at  low settings.  Read  the  book on  the  Apache,
it tells  how  they  intentionally  mismatched  the  mod  tranny  in  hopes  
of  forcing  thru  more audio.  But  it  produced  tons  of  distortion and  
splatter.  Remember  this  rig  and  the Valliant  were
the  last efforts  to  save  AM and  plate  modulation.  It  was not
well  done in  original form.  The  Apache  and  the Valliant  are   both  
great AM  rigs  with  the  correct  mods  done.  Russ


>From: "Bill Smith" <billsmith at ispwest.com>
>Reply-To: amradio at mailman.qth.net
>To: <amradio at mailman.qth.net>
>Subject: Re: [AMRadio] re: Apache audio not good
>Date: Sat, 13 Apr 2002 17:28:42 -0700
>
>Yes, that is how I understand it.  Understanding the difference between a
>"compressor" and "limiter" is difficult, because they do almost the same
>thing.  I think the real distinction is that a limiter is a device used as
>the last processor before a transmitter's modulation stage.  The limiter is
>in position to make sure the transmitter is never overmodulated.   This is
>particularly important in FM transmitters because they can splatter, or
>excessive modulation can exceed the bandpass of the receiver and activate
>the receiver's squelch circuitry.
>
>A compressor adjusts the audio path to provide the largest average signal,
>and is in position to provide maximum "punch".  Usually the difference
>between a limiter and a compressor is a matter of a longer time-constant
>used in the voltage-controlled amplifier stage that is automatically
>adjusted to control the volume.  A compressor will usually not fully 
>respond
>to a strong, very loud pulse, or a "rogue" pulse (similar to a "rogue wave"
>at an ocean beach).
>
>A simple "brick wall" limiter can be made from a couple of LED diodes, 
>wired
>back to back.  Positive audio peaks will light one LED, and negative audio
>peaks will light the other LED.  One can soften the limiting action 
>somewhat
>by placing resistors (or a pot) in series with each LED diode, with a diode
>wired across each pot so that the resistance is effective for only one
>polarity.
>
>The advantage of LED's is they will light when they are limiting (the
>circuit is low-impedance).  The problem, of course is that severe limiting
>occurs when the diodes conduct.  But the circuit provides a concept of how 
>a
>limiter operates, and the pots can be adjusted to provide asymmetrical
>(positive peak) limiting.
>
>73 de Bill, AB6MT
>billsmith at ispwest.com
>
>
>
>
>----- Original Message -----
>From: <SBJohnston at aol.com>
>To: <amradio at mailman.qth.net>
>Sent: Saturday, April 13, 2002 4:40 PM
>Subject: Re: [AMRadio] re: Apache audio not good
>
>
> >
> >  billsmith at ispwest.com writes:
> >
> > >Not necessarily.  A clipper is a limiter.  A limiter need not introduce
> > >the severe distortion a "brick wall" diode clipper will contribute.   
>:-)
> >
> > That's true and you say it well:  "A clipper is a limiter."  If the 
>stage
>in
> > the Apache is a clipper, then the fellow who called it a limiter isn't
>wrong.
> >  The control behind the CW key jack sets the drive to the stage where 
>the
> > peak-limiting is taking place.  Set the drive toward the low end and
>you're
> > just clipping off the peaks that you don't readily hear.  Drive it 
>harder
>and
> > now you're tearing off nasty chunks of the waveform and you can really
>hear
> > it.
> >
> > I've always thought of a limiter as a device that reduces the peak 
>values
>of
> > a signal down toward the average level.  It can rip and tear those peaks
>off
> > (simple back-to-back diodes) or it can gently smooth them off (as in
> > sophisticated audio processing).
> >
> > Some confusion can come in as some folks use the term limiter to cover a
> > device that I know as a "compressor" which adjusts its gain to maintain 
>a
>set
> > average output level.  It has the effect of reducing the dynamic range 
>of
>the
> > signals applied.  But it doesn't peak-limit unless its action is set 
>fast
> > enough top respond to the transients - but then it is a limiter.
> >
> > Words, words, words... sigh.   -grin-
> >
> > 73  Steve
> >
> > sbjohnston at aol.com
> >
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>
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