The jammer you reference above won't work on most drones. Many (most?) consumer-type drones operate in the 2.4 GHz band, which is far above where that jammer operates. Instead, you'll want to grab one of the cheap Chinese jammers for the wifi band and use it. If you are based in the US beware that the US government is starting to crack down on RF jammers imported into the country and is even talking about going after consumers:
http://online.wsj.com/articles/fcc-levels-record-fine-against-chinese-maker-of-cellphone-jammers-1403205812Still, the legal risks are probably much lower than the risk of firing a gun at one of these unless you live in a rural area where discharge of firearms is not prohibited.
I kinda thought the frequency would be wrong. But in concept I think jamming with a dirty, broad spectrum broadcast would be your best countermeasure. It would be very hard to detect compared to a shotgun blast.
If you really knew what you were doing you might even be able to connect to the datastream from the camera. Then you could get a look at the drone operators when they recover the bird. This was done to U.S. drones like the MQ-9. If I remember correctly, it could be done cheaply with off the shelf gear.