These microphones do not work with the CDM-1550 series, even though they are advertised as such. They don't match the impedance and end up sounding overly modulated, raspy and just not producing a clear sound in the end. Some retailers sell them for as little as $9 including shipping! That's why. If you are looking for a nice microphone to control your repeater with DTMF, this one is perfect. But if you really need a microphone to speak, then this isn't it. I bought two and both worked as above.
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