Split carry wave

Thread Starter

phongkem

Joined Nov 19, 2011
23
Hello everybody,
I'm trying to get carry wave from signal in the picture. It's 2 different frequency sin signals mixed together. Could you please give me some advice.
Thanks and best regards.
 

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alfacliff

Joined Dec 13, 2013
2,458
it looks like you are viewing a on air signal from a digital tv station. it takes more than just a few bandpass filters to seperate out the individual signals on the carrier.
 

alfacliff

Joined Dec 13, 2013
2,458
what does the vertical deflection setting have to do with it? if you check the frequency, 56.70, thats channel 2 tv chanel.the horizontal rate is low enough that it shows the individual data chanels on the tv chanel. if you had a spectrum analyzer, the signal would look like a haystack, lots of carriers, each with data. not too sure what the horizontal low frequency componant is, might be hum.
 

vk6zgo

Joined Jul 21, 2012
677
Hello everybody,
I'm trying to get carry wave from signal in the picture. It's 2 different frequency sin signals mixed together. Could you please give me some advice.
Thanks and best regards.
I think you may have found one of the limitations of an inexpensive DSO.
It looks a lot like "aliasing"to me.
If you look at a higher frequency signal at a very long time/div setting.the DSO will in many cases reduce its sample rate below,or very close to the frequency of the observed signal
 

DickCappels

Joined Aug 21, 2008
10,153
You have the two signal sources in series so all you can get is the sum of the two signals. To see the modulated envelope you need to multiply one signal by the other. That can be done many ways.

A small tweak of your circuit will get you some sort of an envelope (not pretty), if your scope has an FFT function you should be able to see sidebands. You might want to follow the mixer with a high pass filter to remove the baseband signal.
 
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