[AMRadio] 7285Kc tomorrow/Saturday

John E. Coleman (ARS WA5BXO) wa5bxo2005 at pctechref.com
Mon Jan 9 10:13:34 EST 2006

I think what Mark is saying is that it it's difficult to tell what
percentage modulation you're at when the wave form is not a sine wave and is
not synced and this is true. You just have to get as close as you can with
out pinching the carrier (not too often anyway).  An automatic gain control
circuit helps a lot with this.  I did with out one for years learning how to
talk by watching the scope.  But it is a lot nicer and more relaxed when you
have one.


-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of W5OMR/Geoff
Sent: Monday, January 09, 2006 5:09 AM
To: Discussion of AM Radio
Subject: Re: [AMRadio] 7285Kc tomorrow/Saturday

Mark K3MSB wrote:

>Yes.  I've tried a scope now and then (I have an old 60 Mhz B&K), but
>truthfully I've never been able to really see when the modulation
>level is 100% or other.  I know what ideal waveforms look like (with
>test inputs),  but I have a hard time with a typical speech waveform. 
> I guess if I'm really at 20% that would be fairly easy to discern. 
>When I used the scope before I was trying to figure out how to tell if
>I was say at 70%, 80%, 90% etc,  and never felt I could do it

Read the John/Don/Bacon page about asymetrical audio.  It's written 
well, it's illustrated well, and completely discusses high-level, plate 
modulated audio and how much you -really- need.

"Operating your AM Rig with out an oscilloscope,
is like driving your car at night without headlights."
(-K4KYV/Don Chester - AM Press Exchange)

73 = Best Regards,

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