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For the NPC mod to work, the limiter is clipped.  So long as the rest of the modification is done as shown by loosecannon on this thread, it won't allow the the negative clipping/distortion to happen.  As was shown in the video. 


Instead, you can get up to 200% modulation before positive peak clipping/distortion occurs.  Clipping out the limiter (removing R276) by itself isn't right.  But with the addition of the NPC mod (adding the resistor, the diode, and relocating the C233 disc capacitor) it will keep it from negative clipping/distorting (look at the top of this page for all of the details).


The mic gain will control the amount of positive rise of peak modulation.  If too much mic gain is applied; then you will get positive peak clipping.  All you need to do is keep the positive peak from clipping by being careful with you mic gain adjustment.


EDIT:

Keep in mind that the output final transistor will be working overtime; as it will be driven harder.  Put a heat sink on the back of the radio behind the driver and final transistor.  Keep the peak wattage about 16 peak watts with a 2 watt dead key @ 200% modulation.  At 1 watt dead key; you should see 8 peak watts @ 200% modulation - BTW.