CB Microphone Basics

A microphone is an acoustic-to-electric transducer or sensor that converts sound in air into an electrical signal. There are several features associated with CB microphones. Some are just for fun, but most have practical uses.

Ceramic- Uses the phenomenon of piezoelectricity—the ability of some materials to produce a voltage when subjected to pressure—to convert vibrations into an electrical signal. This is a rugged, low-cost but high-impedance mic

Power - Power, or pre-amplified, mic's are microphones that require a battery and amplify the audio before it gets to the radio. This is useful for those who speak softly, or may have a weaker signal.

Speaker - Speaker microphones are mic's with the speaker and microphone components in the handset. These types of microphones are typically used with radios developed to work with them like the Cobra 75WXST.

Echo - Echo mic's, as the name would imply, produce an echo sound effect. Deliberately introduces distortion and echo into transmitted audio. Some have a dial to adjust the speed of the echo.

Noise Canceling - A noise canceling microphone uses two elements to reduce background noise and helps filter out additional noise while you talk.

Roger Beep - A microphone with roger beep will transmit a beep when you un-key the mic. This lets the listener know you have ended your transmission.

Dynamic - A dynamic microphone is a basic CB microphone with a ceramic cartridge inside using a magnetic coil and permanent magnet.  These types are considered the stock mics that are included with the CB radio when you purchase it.

Electret - An electret microphone is a basic CB microphone with an electric cartridge inside to convert sound to electrical signals. These mic's can be smaller and less expensive than the dynamic mic's but can only work with CB radios that are wired to receive these types.  Trying to use a dynamic microphone on a radio that needs an electret microphone will make the microphone inoperable.

CB Microphone Pins

The main thing to consider when buying a new mic is the pin configuration. Most newer radios have the 4 pin wiring. Many older models have different wiring, though.

Common basic mics, consist normally of three colored wires and a braid/screen. The braid is the common wire for the TX/RX/Mod and is normally twisted around the modulation wire. If you get this in the wrong place you will be fighting an uphill battle. 4 pin mic sockets are about the easiest to sort out, (the 5 pin din can be very hard to wire as there's not much distance between the pins and can "short out" easily). For a 4 pin configuration put the plug into the radio and look at the solder pins.

Two of these pins will make the radio receive (sound) so find out which two these are by shorting a piece of wire across the pins with the radio on until you find the two that make sound.  One of these pins will also be common to making the radio TX so that pin will be where the braid is soldered to. Once that is soldered on its pin touch each colored wire on the other pin until the sound returns. Solder that colored wire on the other pin. Next you need to find the TX pin. With the mike key depressed touch the other two wires briefly on the TX pin until you find the one that makes it TX. Solder that wire to the TX pin. Finally the modulation wire will go on the remaining pin. Often the modulation wire is the yellow one or it has the braid wrapped round it.  

Common power mics, normally have 4 colored wires and a braid. More often than not the black and braid twist together and go on the earth pin. The blue goes on the Receive pin. Sometimes but less often the blue and braid go together and the black is RX.