PRO-96 Internal Adjustments
From The RadioReference Wiki
This text presumably comes from a service manual and concerns the adjustment of VR2, 3 and 4 (as shown in the pic to the right- click on it to expand. The area surrounded by a red box below the middle of the pic contains VR2,3 and 4)
These VR's should only be adjusted using a calibrated Signal Generator and Frequency Counter. The procedure is as follows: Program three freqs into the scanner in channel 001, 173.3900 002, 173.4200 003, 154.5475 Connect generator to antenna jack set without modulation 173.3900 and connect the counter to TP5. Turn scanner on with SQ CCW and select channel 001. Adjust VR4 until the counter indicates 455 kHz + or - 10 Hz. Select channel 002 and set generator to 173.4200 and adjust VR2 until the counter indicates 455 KHz + or - 10 Hz. Select channel 003 and set generator to 154.5475 and adjust VR3 until the counter indicates 455 KHz + or - 10 Hz.
It has been determined through experimentation that adjusting VR4 has a direct effect on how well the PRO-96 decodes a P25 signal. See message 25 of this Thread for more information