So what is a Jammer?
Def: jam 7. 'To interfere with or prevent the clear reception of (broadcast signals) by electronic means.' - http://www.answers.com/jam
This instructable show you how to build a simple RF jammer/noise generator for 0-128MHZ. The sole purpose of this device is to interfere with the proper function of radio controlled objects.
The best part is that this project is SIMPLE. All of the heavy lifting is done for you by an Parallax Propeller chip. The hardest part is waiting for your components to arrive by UPS.
WARNING: In the US and elsewhere the intentional Jamming of RF Signals is ILLEGAL. The FCC does not look kindly on this type of action.
Also lady ada has a great writeup on this:
Step 1: What is happening
Step 2: Your Parts
Bill of Materials:
B1 3-24 VDC
IC1 Propeller P8X32A-D40 $13
J1 4 pin header
U1 24LC256 $5
U2 LM2937-3.3 (3.3v version) $2
W1 RCA Jack (optional)
X1 5 mhz Crystal
antenna, an ~8"/20.32cm odd length of wire will do
propeller plug for programming $30 or build your own.
Step 3: Diagrams & Code
You can read the .sch file with http://www.expresspcb.com/ExpressPCBHtm/Free_cad_software.htm
The source code (.spin files) are Parallax Propeller objects
The original source code being used in this project was written by Beau Schwabe. Its intent was not for jamming purposes but for controlling a toy RC car his child had received.