What is a Microphone
How to Make this Wireless Microphone Circuit
Let's try to understand how to build a wireless FM microphone circuit.
The mic section actually consists of a mini FM transmitter which is so small that literally it can be accommodated in a space of less a square inch and if its made using SMD, it could well be made within an area of 1 square cm.
Actually the unit can be experimented in many different ways as the parameters involved are truly flexible. The power consumption being negligible allows us to use button cells for the operations. However pencil cells would be more preferable if the unit is intended to be used for long hours of speech transmission.
The main active part of the circuit is the general purpose transistor, while the other supporting passive parts are also very few making the item very compact as far as part count is concerned.
The circuit assembly strictly does not require a designed PCB, nope! And in fact is not recommended either. The whole circuit can be fitted over a small piece of veroboard, or probably if you have a good hand with soldering, you would be able to stitch the parts together over a thin piece of plastic or rubber strip.
The figure shown alongside illustrates the details of the transmitter part, all that’s required for completing the wireless microphone section. A plastic pipe or any similar enclosure may be used for housing the circuit along with the battery and the switch.
How the MIC Circuit Works
However for hobby purpose you may use your home FM radio for the receptions.
Testing and Setting up the Microphone Transmitter
Once the transmitter is built, it may be tested with the following few simple steps:
Connect a 3 volts supply to the circuit, preferably from two AAA pencil cells.
Keep a FM receiver somewhere around the transmitter at about 2 meters from it initially and start tuning the receiver until you find the “null” spot where the “hissing” from the radio suddenly becomes zero.
Now tap or speak loudly over the mic of the transmitter, which should be audible over the receiver clear and loud.
Now take the FM radio further away from the transmitter to about 10 meters and repeat the procedure by readjusting the tuning of the radio until the reception is crystal clear.
The testing of the wireless mic is done and it’s ready to be used.
House the e entire assembly inside a suitable enclosure as described in the above section and you are all ready with an efficient cordless microphone…….Well,.. now nobody can stop you from becoming a home-brewed karaoke rock star.