Reference Oscillator Alignment; Table 13 Reference Oscillator Alignment - Motorola HT-1000 Service Manual

Perform the following procedures in the sequence indicated.
Reference Oscillator
Alignment
Each SERVICE screen provides the capability to increase or decrease
the 'softpot' value with the keyboard UP/DOWN arrow keys
respectively. A graphical scale is displayed indicating the minimum,
maximum, and proposed value of the softpot, as shown in Figure 3.
0
Min.
Value
Adjusting the softpot value sends information to the radio to increase
(or decrease) a DC voltage in the corresponding circuit. For example,
pressing the UP arrow key at the Reference Oscillator screen instructs
the radio microprocessor to increases the voltage across a varactor in
the reference oscillator to increase the frequency.
In ALL cases, the softpot value is just a relative number corresponding
to a D/A (Digital-to-Analog) generated voltage in the radio. All
standard measurement procedures and test equipment are similar to
previous radios.
Adjustment of the reference oscillator is critical for proper radio
operation. Improper adjustment will not only result in poor operation,
but also a misaligned radio that will interfere with other users
operating on adjacent channels. For this reason, the reference
oscillator should be checked every time the radio is serviced or once a
year, whichever comes first. The frequency counter used for this
procedure must have a stability of 0.1 ppm (or better).
1. From the SERVICE menu, press F2 to select TRANSMITTER
alignment.
2. Press F2 again to select the REFERENCE OSCILLATOR softpot.
3. Press F6 to key the radio. The screen will indicate that the radio is
transmitting.
4. Measure the transmit frequency on your service monitor.
5. Use the UP/DOWN arrow keys to adjust the reference oscillator per
the targets shown in Table 13.

Table 13 Reference Oscillator Alignment

BAND
VHF
UHF
800/900 MHz
Figure 3 Softpot Concept
MAEPF-22858-O
TARGET
0 to 300 Hz
0 to 300 Hz
0 to 300 Hz
15
Max.
Value
19