Hello, You are not providing enough information to answer your question. You mention you are using an E4438C but you don't state what type of signal you are trying to output. Is it CW? Is it WLAN? Are you trying to apply AM? Why are you trying to set the BW and to what value are you hoping to do so? Please provide more information and I will try my best to answer your question.
You are not providing enough information to answer your question.
You mention you are using an E4438C but you don't state what type of signal you are trying to output.
Is it CW? Is it WLAN? Are you trying to apply AM?
Why are you trying to set the BW and to what value are you hoping to do so?
Please provide more information and I will try my best to answer your question.