Motorola GM1200E Service Manual download pdf (Page 50)

GM1200E Tuning Procedure

4-4 Radio Tuning Procedure

1. From the Service menu, select Transmitter Alignment.

2. Select RF Power Tuning to open the RF power tuning window. The window will indicate the

transmit test frequencies to be used.

3. Select Point 1 value of the ﬁrst frequency.

4. Click Toggle PTT to key the radio. The status bar will indicate that the radio is transmitting.

5. Measure the transmitter power on your power meter.

6. Enter the measured value in the box Point 1.

7. Select Point 2 value of the ﬁrst frequency.

8. Measure the transmitter power on your power meter.

9. Enter the measured value in the box Point 2.

10. Click Toggle PTT to dekey the radio.

11. Repeat steps 3 - 10 for all test frequencies shown in the window.

12. Click Program to store the softpot values.

1.5 Reference Oscillator

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. The frequency counter used for this procedure must have a stability of 0.1

ppm (or better).

1. From the Service menu, select Transmitter Alignment.

2. Select Reference Oscillator to open the reference oscillator tuning window. The tuning window

will indicate the target transmit frequency.

3. Click Toggle PTT to key the radio. The status bar will indicate that the radio is transmitting.

4. Measure the transmit frequency on your frequency counter.

5. Adjust the reference oscillator softpot in the tuning window to achieve a transmit frequency

within the limits shown in table 4-2.

6. Click Toggle PTT again to dekey the radio and then press Program to store the softpot value.

1.6 Front-End Pre-Selector

Alignment of the front-end pre-selector is normally not required on these radios. Only if the radio has

poor receiver sensitivity or the pre-selector parts has been replaced the following procedure should

be performed. The softpot value sets the control voltage of the pre-selector. Its value needs to be set

at 7 frequencies across the frequency range.

1. Set the test box (GTF180) meter selection switch to the "Audio PA" position and connect a

SINAD meter to the "METER" port.

2. From the Service menu, select Receiver Alignment.

3. Select Front End Filter to open the pre-selector tuning window. The window will indicate the

receive test frequencies to be used.

Table 4-2 Reference Oscillator Alignment

RF-Band Target

All bands ±150 Hz

1 2 ... 45 46 47 48 49 50 51 52 53 54 55 ... 61 62

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Motorola GM1200E Service Manual Page 50