Actually, I have not seen any rules for jamming someone's transmissions. The closest thing to it is the anti-bugging device that's listed in the book.
As for jamming in space, it would not surprise me if they left it out because you're not allowed to 'jam' another ship's transmissions. Realistically, this is something that is amazingly hard to do.
First, all space ships are going to be immensely shielded to resist the kind of harmful radiation that would screw up their comms.
Second, the distances involved would require an energy allotment for the jamming device that would rival the heaviest weaponry, and even then I'm not sure it's doable.
Third, in order to effectively 'jam' a target you need to figure out what frequency their comms are operating on. If it is an uncoded, single channel broadcast, then it's not too hard to lock into the signal and then spoof the broadcast. This is done by emitting an extremely high powered emmission on the same frequency, thus overpowering the transmission from the 'jammed' vessel.
However, any vessel worth its salt will be using a frequency hopping technique to broadcast its transmission. This means it doesn't stay on the same frequency for more than a fraction of a second before it jumps to a new frequency. With the advanced technology this will probably occur several hundred times per second and occur in a nonsequential nonrepeating fashion. The only person who's going to be able to listen will be another with the same communication security. The only way you're really going to be able to 'jam' this type of communication is to somehow get a hold of his comms protocols and pump a high powerer broadcast out.
Fourth, the other thing to worry about is that though communications can travel faster than light by using the jumpgates and a carrier signal, they still only travel at near light speed across normal space. This means that you might not have to jam someone in order to keep them from calling for help in time. The down side to this is that in order to jam someone you have to start broadcasting before they do or their message will leave their ship before your jamming signal arrives. Now in most tactical situations the range is short enough that this really won't matter, but in open space you need to be aware of this.
Fifth, a jamming signal is high powered. This means that anyone with the paranoia to be looking will find it. Unfortunately for the jamming vessel, it is fairly easy to track the signal back to its source. So don't expect to stay hidden if you do this.
I'll leave it at that, but if you have any questions about all of this let me know.
