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Posted on Wednesday, November 28, 2001 - 9:06 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Galaxy Melaka Transmitter Alignment:

Required Test Equipment:

a. RF Wattmeter
b. 50 Ohm Dummy Load
c. Frequency Counter
d. Oscilloscope (30 Mhz)
e. Audio Generator (2 tone)
f. DC Voltmeter with DC current capability
g. Optional FM Deviation Meter
h. Optional Spectrum Analyzer

SETTINGS: Clarify to 12:00 position , Channel 19 regular CB band , Mode: USB , TX mode , Microphone Gain Minimum.

1)Remove the PCB Jumper connecting TP-7 , 8 and 9 as shown in Picture #1.

Picture #1

2)Connect DC Amp Meter between TP-9 (+) and TP-8 (-) as shown in Picture #2.

Picture #2

3)Driver Bias: Adjust VR11 for 200 mA (Picture #3 and #4).

Driver Bias
Picture #3

Picture #4

4)Connect DC Amp Meter between TP-9 (+) and TP-7 (-) as shown in Picture #5.

Picture #5

5)Final Bias: Unsolder the CENTER lead of the driver transistor as shown in Picture #6.

Picture #6

6)Adjust VR10 for 150 mA (Picture #7 and #8).

VR 10
Picture #7

Picture #8

7)Restore the driver pin that you unsoldered above.
8)Remove DC Current Meter and restore shorting PCB before continuing as shown in Picture #9.

Picture #9

9)Microphone gain to maximum. Inject 50 mV two-tone audio signal into microphone and adjust L43 , L44 , L42 , L40 and L33 (Picture #10 and #11) for maximum RF power output on RF Power Meter or Scope.

Picture #10

Picture #11

10)Remove injected audio signal.
11)Turn Microphone gain all the way counter clockwise (off).
12)Carrier Balance: Adjust VR7 (Carrier Balance) for minimum carrier (power) while viewing power on meter or oscilloscope. (VR7 in Picture #12).

Picture #12

13)Turn Microphone gain all the way clockwise (on).
14)Inject 100 mV two-tone audio signal into microphone.
15)SSB ALC: Adjust VR12 for 12 watts P.E.P. (Picture #13)(Factory default).

Picture #13

16)Switch to mode: AM , Microphone gain to minimum.
17)AM Power: Adjust VR13 to 4 watts dead key on power meter. (Picture #14)(Factory default).

Picture #14

18)RF Meter: Adjust RF Meter calibration VR 8 to set the transmit power meter on the radio to match power meter used for testing.(Picture #15).

Picture #15

19)Inject 100 mV single tone in the microphone.
20)AM AMC: Adjust VR14 to 95% modulation on the test meter.(Picture #16)(Factory default).

Picture #16

21)Mode to FM:
22)Inject a 1 Khz tone at 20 mV into microphone.
23)Adjust VR5 for maximum deviation of 5 Khz on the FM deviation meter. (Picture #17).

Picture #17

This completes the Transmitter alignments , continue with next topic.
(Receiver Alignment)

Questions? Contact