calculate the bandwidth required for each of the following AM stations.?

Question

* Modulating signal with bandwidht of 7khz.
* Modulating signal with frequencies of 1000 to 6000Hz.

Answer 1

If you are talking about regular amplitude modulated signal, it has the sideband on both sides of the carrier. Each sideband takes the full bandwidth of the signal it is modulating it. Therefore, if the signal is 7khz wide, the resulting signal will have 14khz bandwidth.

As to your second question, the 1khz signal will already create the bandwidth of 2khz for the same reason. Therefore, if the highest frequency is 6khz, then the resulting bandwidth is 12khz.