[AMRadio] Use of an oscilloscope to monitor am audio

Jim Wilhite w5jo at brightok.net
Sat Mar 18 16:25:12 EST 2006

Jim I have a Tek 465M that I use.  I also have a tuner with a built in balun 
that I do not use.  I use the tuner with coax  when operating off the 
resonance of my antenna.  My scope and probes are good to 100 Mc and provide 
enough bandwidth to monitor up to 29 Mc.  If your 453's bandwidth is less, 
you won't be able to go as high.

So I take my 10:1 probe and attach to the output of the balun terminals. 
One to the ground clip and the other to the probe.  That provides enough 
isolation to give a waveform display.

The waveform is very difficult to follow as to assure 100% modulation.  To 
be accurate, one should use the trapezoidal pattern.  The peaks and valleys 
of a waveform cannot be seen accurately on a scope unless you have a storage 
scope.  Others have suggested means of building a sampler for this purpose, 
and I thought I would mention another way.

73  Jim

>I have a Tektronix model 453a scope and I would like to know how it can be 
>used to monitor transmitted signals.  Do I need extra hardware or an 
>interface of some type to obtain the trapezoid pattern?  I know some scopes 
>designed for amateur radio have this feature built in so I wonder if my 
>scope can be used for this?

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