AM waveform in frequency domain

AI Thread Summary
The discussion revolves around sketching the frequency domain for a specified AM waveform, with a focus on identifying total bandwidth and frequency. Participants question the meaning of "k" in the cosine terms, suggesting it may represent a scaling factor, potentially indicating a need to adjust the frequencies to a more standard format. There is uncertainty about whether the vertical axis should represent peak voltage or RMS voltage, prompting a recommendation to refer back to course notes for clarification. The original poster seeks validation of their frequency domain sketch and appreciates any guidance on these technical aspects. Overall, the conversation highlights the complexities of interpreting AM waveforms in the frequency domain.
fran1942
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Hello, I need to sketch the frequency domain for the following AM waveform showing total bandwidth and frequency.
8sin(2pi500kt - 4cos(2pi530kt) + 4cos(2pi(470kt)

I have attached an attempt I have made.
Does anyone know if I have this correct or not ?

Thanks kindly for any input.
 

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What does that "k" mean in cos(2pi530kt)?
 
sorry I don't know what that is referring to. We were not told.

Do you think I have the frequency domain sketch correct based on what we do know?

Thanks for your help.
 
Sorry, I can't give an authoritative answer. But I'm wondering whether you might be meant to label the frequencies as 500k, 503k, etc., that k seems to be some scaling factor. Are you sure it's not meant to be x103 and you have changed it to a k?

Also, perhaps someone else can confirm that the vertical axis is okay as the peak value. I'm just wondering whether it should be RMS. Can you refer back to an example in your notes to confirm that peak voltage is what you need to use here? (I've forgotten.) https://www.physicsforums.com/images/icons/icon9.gif
 
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