[AMRadio] Frequency Response


Crawfish crawfish at surfmore.net
Sat Sep 25 00:37:25 EDT 2004


The phone company is responsible for that illogical 3 kHz upper limit. The
consonant sounds are missing unless you go above 4.4 kHz( 5 kHz is a good
compromise).

Joe W4AAB
----- Original Message -----
From: Gary Blau <gblau at w3am.com>
To: Discussion of AM Radio <amradio at mailman.qth.net>
Sent: Friday, September 24, 2004 11:20 PM
Subject: Re: [AMRadio] Frequency Response


> IMHO, the best approach is to terminate the mod xfmr (or any audio xfmr)
> for best transient (square ware) response of the modulated envelope, not
> just an arbitrary upper frequency.
> Adjust for best stability, least overshoot and ringing on leading edges,
> and the least tilt.  Check it at mid freq's, say 1khz, as well as low
> (50hz) and high (5khz).  It's easier to see the tilt on the low end, and
> the overshoot on the midrange.  All of these disturbances rob modulation
> power from you, as you have to reduce average modulation level to keep
> the peaks from overmodulating.
>
> Cleaning it up will help maximize modulation control, sometimes as much
> as several db.  This in turn increases potential average loudness which
> is the name of the game.
>
> The best place for audio bandwidth control/limitation is in the low
> level audio chain.
> As to where to roll it off, I'd suggest 5khz, but I like to make it
> variable depending on conditions.
> With only 3KHz you might as well be on SSB.
>
> g
>
>
> Edward B Richards wrote:
> >
> > Tom;
> >
> > I believe the standard for communications is 300 to 3000 CPS +/- 3 dB.
> >
> > On Fri, 24 Sep 2004 14:54:49 -0800 "Tom Elmore" <tom at telmore.com>
writes:
> > > I am in the process of restoring a Stancor 60-P transmitter to
> > > service. I
> > > have replaced all the capacitors in the power supply and in the
> > > audio
> > > amplifier sections.  I would like to terminate the modulation
> > > transformer
> > > with the correct resistance and check for frequency response on my
> > > scope.
> > > What is a good ballpark response that I should use for operating AM
> > > in the
> > > amateur bands.
> > >
> > > Thank You
> > > Tom Elmore KA1NVZ
> > > Anchorage  Alaska
>
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