Hi Felipe,
It would take some investigation to know what the proper bias voltage is.? Perhaps HFSignals could help the group with this?
Electret elements do have a maximum operation voltage depending on the specifications of the FET transistor inside.? In the ubitx the bias voltage supplied is just whatever is supplied to the rig, so it could be 12V, 13.8V, or more.? This could easily be over the limit for an electret element.
It seems like the supplied Baofeng microphones are made for their HT's.? If that is so, they are probably using a lower voltage electret element where the bias voltage should be something more like 3V.? Someone with a Baofeng HT may want to measure the bias voltage the HT supplies on the external mic port.
Electret elements can easily be tested with just a load resistor of 2.2k and an electrolytic blocking capacitor of about 1uF.? Supply the microphone with about 3V through the 2.2k resistor.? Measure the current in this circuit and is should be somewhere around 0.2-0.5 mA.? Audio output can be measured with a multimeter on the AC mV range.? Put one lead on the capsule negative? terminal, and the other lead on the negative capacitor lead and the positive capacitor lead on the positive capsule terminal.? Blowing on the mic should then easily generate 50mV or more.? This will obviously not check audio quality, but it is a good first check.
Given that these mics are having the two pin plugs cut off and a 1/8 phone jack installed, it could be that there are wiring mistakes.? Are the mics individually tested after the plug installation?
73,
Mark.
