[AMRadio] New Year's Resolution-Getting Back on AM!


D. Chester k4kyv at charter.net
Wed Dec 27 12:31:59 EST 2006


> There are others that say that monitoring your envelope pattern isn't
> good enough, if you have a scope... you should be watching the
> Trapezoid pattern, instead.

One problem with monitoring the trapezoid pattern all the time is that it 
will burn a dark vertical line onto the face of the scope tube, where the 
unmodulated carrier appears.  The trapezoid pattern is useful for indicating 
the linearity of the modulated stage, but the envelope pattern gives a 
better idea of the actual quality of the signal, since flat-topping and 
waveform distortion are easily apparent.

The evelope pattern will burn a horizontal line where the bright no-signal 
baseline appears, if you don't disable the scope when not transmitting. 
This can also be a problem with CW and SSB operation, since the bright 
baseline is there during pauses in modulation or keying, just as the 
vertical line is there during pauses in AM modulation when using  the 
trapezoid pattern.

Don, K4KYV

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