Jovian radio emissions are often predictable. The most reliable sources are Io-A, Io-B and Io-C. The dates and times for predicted radio noise storms can be obtained from links on the Jupiter Radio Storm Predictions page or by using Radio- Jupiter Pro (special Jove edition). This program is available free for download from Radio JOVE Software page and is also included on the Radio Jove Reference CD.
Solar emissions are not predictable, but often occur when there is an active sunspot region on the visible portion of the solar disc.
Whether you are observing Jupiter or the Sun it is important that your "target" be in the antenna beam while you are observing. Radio-Jupiter Pro generates a real-time display showing the location of both the Sun and Jupiter above your horizon and indicates when these sources are within the beam of your Jove antenna.
So, if you want to know when to listen, check out the Jove Web site or fire up your copy of Radio-Jupiter Pro and get familiar with its many useful features and displays.