Wireless guitars are great, without cables to trip on the life expectancy of an energetic guitarist is greatly increased. However, they are expensive, way more expensive than wireless microphone systems. In fact, if you're like me, you might happen to come into a wireless microphone system for free. Using it for your guitar is a ultra-simple hack that almost anyone can do in less than an hour.
Step 1: Tools and Materials
Drill and 3/8" bit
Step 2: Disassemble
Before you rip into the mic, test that it works! It could save headaches later.
Most of these mics just screw together to allow for the occasional cleaning. Twist the top off and pull out the microphone-holding center piece. Cut the wires as long as you can so that there is enough slack that the wires don't break when the microphone is screwed back together. If there isn't enough you may need to extend them a few inches.
Step 3: Drilling The Top
Using the 3/8" drill, drill a hole in the top of the microphone, through the mesh. Using a drill press and vice is best for this, since it is likely to snag on the mesh. Do be careful.
Once the hole is drilled, apply some tape around the inside, on the top of the mesh, and beneath. Its likely that if the guitar jack makes electrical contact with the housing of the mic, it won't work properly. I had this problem and I solved it with tape.
Step 4: Wire the Jack
Strip the ends of the two old microphone wires and solder them to the lugs of the 1/4" guitar jack. I guessed that the red one was signal and green one was ground, but I don't think it matters. If there is an issue, try flipping the wires.
Step 5: Re-assembly
Push the jack up into the microphone head and attach using the included washer and nut. Tighten with the 1/2" wrench.
Screw the head of the mic back onto the body. Plug it in and test it out!