This is something I did 20 years ago to my younger brother that was in tech school learning electronics.
He was interested in cb radio but was discouraged about the background noise and 'skip'.
So as a prank I put this box together.
I was so successful at fooling him he took 'my invention' to tech school to show off, the instructor was not amused when they took the cover off to exam how i did it. He was kidded for months about his invention, and was so mad at me for months.
The idea is 'that by flipping a switch', extensive noise filtering and reconstruction algorithms rebuild the original signal giving you an almost silent radio when no one is talking.CB enthusiasts wow over it until they try to use the radio, and realize the signal cant get out.

Step 1: Acquire the Parts

PARTS LIST
2 BNC case connectors
1 spdt switch
1 dummy load
1 project case
some wire

if you can pick them up from the scrap box much better, otherwise the parts can be bought from radio shack for under 15.00

you'll also need a drill, screwdriver, pliers, soldering iron, solder

Step 2: Wiring

following the schematic is easy, simply when the switch is set the first direction the 2connectors connect the antenae
flip the switch and the radio is connected to the dummy load, so that power back feed doesn't burn it out.
the connectors and dummy load all connect to a common ground,usually the case

Step 3: Close Up and Laugh

mount the connectors and switch, put the cover on.
make a label for the switch and connectors. I used a label gun way back then.

Find a friend or two that use cb radio and show them your fantastic new invention. let them know how much timeit took to work out the filtering and reconstruction algorithms,the late nites you spent working the bugs out. The pc boards you had to build, the chips u had to buy and program.
connect it between their radio and antennae, the fact that it still recieves radio signals will impress them!
then tell them to turn the squelch off, cause they wont believe how quiet the cb is with the noise removed.
then flip the switch and just wait for the praise to roll off their lips.
flip it on and off several times to prolong the praise and delay the inevitable discovery, offer to build one for them at a cost, above all have fun with it