Vco Attenuation - Motorola CP150 Basic Service Manual

4-8
5. Press PTT Toggle again to key up the radio at the selected frequency point.
6. Repeat steps 3-5 for the remaining test frequencies (F2-F7).
7. Press Program to store the softpot values into the radio's codeplug.
8. Exit the Transmit Low Power function.

4.4.4 VCO Attenuation

Note: Modulation Balance Tuning must be done first. The Transmit Deviation Limit softpot
sets the maximum deviation of the carrier. Tuning is performed for all (12.5 kHz, 20
kHz and 25 kHz) channel bandwidths. Tuning for 25 kHz channels must be done first
for all frequency points. Tuning for 12.5 and 20 kHz channels determines only the
offset to the previously tuned deviation for 25 kHz tuning channel spacing. For 12.5,
and 20kHz channels, only the last non-0 transmit frequency point (normally F7) is
used for tuning. The 30 kHz channel bandwidths that use 5.0 kHz maximum system
deviation are covered by the 25 kHz tuning.
4.4.4.1 VCO Attenuation 25 kHz
1. Under the Tx Align menu, select VCO Attenuation 25 kHz (Figure 4-6).
2. Begin with the lowest frequency. Select the thumb of the slider at the lowest frequency point and
then press the PTT Toggle button to key up the radio at the corresponding frequency point. The
spin control can also be toggled via its up/down arrow buttons. The softpot value can also be
typed into the edit control (press ENTER to confirm your selection/send a softpot value).
3. Inject 1 kHz at an appropriate level until 2.3 V rms is measured at the AC/DC METER (radio
input) if using test box RLN4460.
When using test box RLN4460:
• Set the METER OUT toggle switch to the "MIC PORT" position
• Set the METER OUT selector switch to "MIC".
• Inject a 1 kHz tone with the levels given below for each radio model to AUDIO IN.
• Measure the level at the radio input at the AC/DC meter.
Figure 4-6. VCO Attenuation Window (12.5 kHz)
Transmitter Alignment Options