[AMRadio] Use of an oscilloscope to monitor am audio

SBJohnston at aol.com SBJohnston at aol.com
Sat Mar 18 18:40:49 EST 2006

Earlier I wrote:

>If the scope has an X/Y mode, you can go beyond the usual 
>envelope pattern you get from putting RF on the X input... In my 
>professional work with AM, I find you can get a very useful pattern 
>by putting RF on the X input and line-level modulating audio on the Y.   
>It forms an ellipse that closes on 100% negative.  I find it easier
> to see the compression/limiting action as shades of intensity 
>on this waveform.

As I was driving home from the grocery store this afternoon, I realized that 
I suffered a brain-fade on this description.  The above procedure gives you 
the trapezodial display, not the ellipse I was intending to describe.  To get 
the ellipse, put RF from the transmitter on both the X and the Y inputs, 
preferrably with a fairly lengthy cable between the two so there is a bit of a phase 
difference, and you get the ellipse that closes the eye on 100% negative.

Sorry for any confusion my error might have caused.  And I wasn't drunk or 
anything... A mind is a terrible thing to waste...

Steve WD8DAS

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