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

 

 

15

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Min.

 

 

 

 

 

 

Max.

Value

 

 

 

 

 

 

Value

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 3

Softpot Concept

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.

Perform the following procedures in the sequence indicated.

Reference Oscillator Alignment

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

TARGET

 

 

 

 

VHF

0 to 300 Hz

 

 

UHF

0 to 300 Hz

 

 

800/900 MHz

0 to 300 Hz

 

 

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Image 41
Motorola HT 1000 service manual Perform the following procedures in the sequence indicated, Reference Oscillator Alignment