Motorola CP150 Basic Service Manual page 39

Transmitter Alignment Options
Compensation alignment balances the modulation sensitivity of the VCO and reference modulation
(synthesizer low frequency port) lines. The compensation algorithm is critical to the operation of
signaling schemes that have very low frequency components (Digital Private-Line) and could result in
distorted waveforms if improperly adjusted. To perform Modulation Balance tuning, follow the
following steps.
1. Under the Tx Align menu, select Mod Balance Attn (Figure 4-4).
2. Begin with the lowest frequency (i.e. the first frequency point from the top). Pressing PTT Toggle
without selecting any slider control at the corresponding frequency point will key the radio up at
the first frequency point.
3. Inject 80 Hz at an amplitude of 1.78 V.
4. Record the deviation obtained. Typical values should range from [(1.70-2.30 kHz. Modulation is
only tuned in the 25 kHz channel spacing mode)].
5. Inject 3 kHz. Set the amplitude to 1.5 V.
6. Change the modulation balance attenuation setting until the Tx deviation is as recorded in step 4.
7. Inject 80 Hz at an amplitude of 1.78 V.
8. Check the deviation again. If the Tx deviation changes, record the reading and repeat steps 5-8
until the Tx deviation remains the same.
9. Press PTT Toggle to dekey the radio. Choose the next frequency, key up and repeat steps 3 to 8
until all seven tuning points are done.
10. Program the softpot value by pressing the Program button.
11. Exit the Modulation Balance Function.
Figure 4-4. Modulation Balance Window
4-5