Software-defined radio and widespread software-controlled PLL synthesis for RF game changes. Things like RTL-SDR can be any radio station you like on almost any frequency you like. But not every SDR or PLL system opens the door to configuration for you, the end user. That was the problem [vgnotepad] faced when trying to connect a Sennheiser wireless microphone to some receivers. They did not use the same frequencies, although the transmitter was programmable. The solution to this is obvious – hack the transmitter!
The post is just one part of several parts and if you read to the end, you will learn a lot about what is inside the device and how to break it. Fortunately, the device uses a PIC processor, so accessing the software was not a big deal.
The PIC uses I2C to communicate with the configuration EEPROM, so the little eavesdropping in the bus has come a long way. Throwing things away led to finding the frequency settings. By the sixth part of the post, everything is working great.
If you need a primer for PLL, Start here. Or build your own with the Arduino.