The short answer is yes. When you schedule an activity for broadcast, then edit the activity before the scheduled date and time and save the changes, you will need to reschedule the activity in order to ensure the updated revision of the activity will be sent to your subscribers.

If you have made changes before a scheduled broadcast, follow this process:

1. Cancel the scheduled broadcast
2. Make any changes to the activity.
3. Save the activity
4. Approve the new revision
5. Reschedule the activity

To ensure the revision content that is scheduled to send is the content that you want your subscribers receive, in the activity preview section, click on the 'Revision' drop down menu and the newly scheduled revision will be marked with '(deployed)' to the right hand side of the revision number.

If you have an activity that has already started broadcasting, see this article about using the deploy and resume buttons.