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APCO P-25 Sound Quality Fine Tuning
With each APCO Project 25 system, particularly at 800MHz, the sound quality (C4FM
Demodulation Threshold) may need to be fine tuned specifically for that system. If the
scanner is not adjusted correctly, the P-25 voice transmissions will sound robotic or
unintelligible.
To adjust the sound quality to match the P-25 system you want to monitor follow these four
steps:
1. While monitoring a specific APCO P-25 frequency, press the ▲/HOLD key.
Note: In the Trunking mode, press the TRUNK key instead of the ▲/HOLD key.
2. Press and hold the number 9 key.
3. On Line 1 of the screen you will see SOUND QULTY: 0050 (for example).
This shows the Sound Quality. The lower the level the better the Sound Quality. For
better Sound Quality rotate the VFO up or down. As the threshold adjusts in
increments of 50 at the bottom of the screen watch the Sound Quality level increase
or decrease and continue to rotate the VFO until you have achieved the lowest
Sound Quality level.
Note: • When APCO P-25 signal is not received, SOUND QULTY: ****
appears on the display.
• You must have the BCi25D card installed and have an APCO P-25 signal
during this adjustment.
• You can also use the ▲ and ▼ keys to adjust the sound quality.
- A chart showing the Threshold Adjustment Range is listed below.
Threshold Adjustment Range
Note: • The above Min and Max values are the calculated values that can
be assigned theoretically, and the values are not to guarantee the
operation of the unit.
• The mid threshold value will not change while adjusting the upper and lower
limits.
SOUND QULTY:0050
867.8375 P25
Low Mid Upp
0533 1985 3342
Lower Mid Upper
Band
Min Default Max Default Min Default Max
800MHz 33 533 1883 1985 1992 3342 3842
UHF 33 633 1883 1985 1992 3342 3842
VHF 158 658 2058 2085 2190 3590 4090
BC785D 11/8/2 1:01 PM Page 70