Re: ALC implementation

Posted by Richard Corfield on Jul 13, 2019; 7:35am
URL: http://elecraft.85.s1.nabble.com/ALC-implementation-tp7653437p7653779.html

The compression modulates the signal. That will have a fourier transform of
its own. If we think of it as a simple amplitude modulation then, as for AM
signals, the spectrum of the original signal will be combined (convolved)
with upper and lower sidebands representing the spectrum of the compressor.
Our ears don't notice (unless we're sound guys listening to a pop song
thinking "They've squashed those dynamics to death" ;-) ) but maybe a
digital mode will.

The transmitted signal is constrained to the IF passband so you stay within
band. The compression frequencies and hopefully amplitude are both small so
the artefacts it introduces into the spectrum should also be both narrow
and small.

 - Richard


On Fri, 12 Jul 2019 at 22:01, Wes <[hidden email]> wrote:

> What distortion?
>
> On 7/12/2019 1:15 PM, Jim Rhodes wrote:
> > Nothing when it is done correctly on a mode that can stand the
> distortion. I
> > personally won't use it on digital modes as my rigs tend to turn it off
> by
> > default.
> >
> > Jim Rhodes
> > K0XU
> >
> > On Fri, Jul 12, 2019, 15:10 Wes <[hidden email]
> > <mailto:[hidden email]>> wrote:
> >
> >     And what exactly is the problem with compression?  It's used all
> over the
> >     place.
> >
> >     Wes  N7WS
> >
> >     On 6/28/2019 11:38 AM, Brian Denley wrote:
> >     > I have always thought that ALC is not appropriate for power
> control.
> >     It’s a protection system.  Over use of ALC acts like compression.
> No?
> >     >
> >     > Brian
> >     > KB1VBF
> >     > Sent from my iPad
> >
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