Motorola MC Micro Audio Modification


Cut the left jumper (JU602) and solder together the right jumper (JU601) for FLAT audio

Change the three resistors (R614 – 33kOhm, R615 – 100kOhm and R616 – 100kOhm) to half the value: ~15kOhm, 47kOhm, 47kOhm.



Change capacitor C608 – 33nF to 1nF:



Solder a 10uF electrolytic from pin 4 of U551 to pin 3 of the DB15 connector (cut pin 3 and change from the original audio output to this).


    • John Gumb
    • April 21st, 2013

    what does this modification actually do? My McMicro could do with a bit more treble.

      • admin
      • April 21st, 2013

      Hello John,

      This modificiation makes the mc micro pass audio up to ~7khz which is needed for noise measurements that is not affected by the regular voice from operating. The TX mod only affects the sound passed thru the transmitter but the RX mod uses a point in the audio chain that is before the squelch so when no one is transmitting you will have only noise.

      73 de SA0AZT, Mattias

  1. No trackbacks yet.