[AMRadio] re: Apache audio info; the REAL story

[russ dworakowski]

Thank you Pete,  I was wondering  how  the  front  panel control  became
the clipper control.  Russ


>From: manualman at juno.com
>Reply-To: amradio at mailman.qth.net
>To: amradio at mailman.qth.net
>Subject: Re: [AMRadio] re: Apache audio info; the REAL story
>Date: Sun, 14 Apr 2002 00:42:28 -0700
>
>Applies only to a stock Apache:
>
>Apache manual dated 1959:
>
>Page 7, paragraph 5:
>Two gain controls are provided in the Apache modulator. The audio gain
>control (THIS IS THE FRONT PANEL CONTROL) between the first two stages of
>the speech amplifier operates as a combined gain and CLIPPING CONTROL.
>The level control (THE CONTROL BEHIND THE KEY JACK) serves to set the
>100% modulation level. The gain control (front panel control) can be set
>to give normal unclipped modulation by merely setting the peak input to
>the clipper just at the threshold of clipping (  when the peak to peak
>voltage of the audio signal exceeds approximately 6 volts, the diodes
>(6AL5) conduct and prevent further increase in amplitude ). The level
>control (behind the key jack) can then be set to give 100% modulation.
>Thus, by further increasing the gain (FRONT PANEL CONTROL), the input to
>the clipper is increased and more and more clipping can be introduced
>without overmodulating the carrier due to the limiting action of the
>clipper.
>
>Page 94, paragraph 8:
>To test phone operation... and rotate the audio gain control (THE FRONT
>PANEL CONTROL)  to the position that gives the amount of speech clipping
>desired. With high impedance crystal or dynamic microphone, 10 percent
>rotation of the audio control (THE FRONT PANEL CONTROL) will give 0 DB of
>clipping, 20 percent will give 9 DB, 30 percent ....etc. The recommended
>level of clipping for general communication is about 12 DB, which is
>produced with about one-quarter of a turn from full CCW on the audio gain
>control (THE FRONT PANEL CONTROL).
>
>It's been that way in the manual for 43 years. You guys have come up with
>some very creative and confusing dissertations on Apache audio.
>
>Pete, WA2CWA
>
>On Sat, 13 Apr 2002 19:40:54 EDT SBJohnston at aol.com writes:
> >
> >  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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> > http://mailman.qth.net/mailman/listinfo/amradio
> >
>
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