There is this preachertype who comes to campus and he is impossible to
ignore because he uses a wireless PA system. Is there a way to get a
wireless mic or some other transmitter and piggyback onto his wireless
PA system so others can enjoy freedom of speech using his PA? If so,
what would we need to do this? Please explain it so a doofus (me) can
understand.

I posted the above on related newsgroups and I have learned the
following:
1. It's all probably illegal and the Patriot Act will put me in prison
forever for even considering it.
2. It's definitely doable but I will need to identify the frequency
the wireless mic is transmitting on and find another microphoned
transmitter device that will allow me to override his wireless mic with
a message of my own.

So the question remains: what is the name of this "microphoned
transmitter device" and where can I find one or find the plans for
building one?

Thank you.