The UAVs have two alternative systems for communication.
Line of sight radio :
In the military C-Band 500 - 1000 MHz that can be jammed with simple spark-gap radio
Satellite communication :
In the Ku-Band between 10.95 - 14.5 GHz, and the satellite can be jammed.
The Uplink-Band to the satellite is 13.75 - 14.5 GHz
The Downlink-Band from the satellite is 10.95 - 12.75 GHz
And you should jam the Uplink frequencies with a jammer directed at the satellite.
As you can see in the specifications, the satellite link system uses the same civilian commercial technology as television broadcasting companies.
If you jam the communication, then the operator becomes blind and the UAV will fly around until it crashes or the fuel is gone. But you must kill both links of communication to kill any rescue.
There are a limited number of satellite channels available which means that the satellite link becomes a bottleneck. The satellite is therefore used as a backup and jammer-rescue channel and for single special operations from far away from the target, while C-band radio is used for multiple simultaneous operations from near the targets. Every military base have their own UAVs that must be operated through the C-band radio. C-band radio is also reported to be used for take off and landing. Which means that the C-band radio is your primary target. The C-band radio is also easier to jam.
Article complet : http://privat.bahnhof.se/wb907234/killuav.htm