Galaxy dx2547 Service Manual

DX 2547

CHAPTER 1

SPECIFICATIONS

1.0 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.1 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.2 Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

TABLE OF

CONTENTS

PAGE

CHAPTER 2

OPERATION

2.0 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.1 Control and Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.1.1 Front Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.1.2 Rear Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.1.3 Frequency Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.2 Microphone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.3 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.3.1 Procedure to Receive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.3.2 Procedure to Transmit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.4 Alternate Microphones and Installation . . . . . . . . . . . . . . . . . . . . . . . . . 10

CHAPTER 3

CIRCUIT DESCRIPTION

3.0 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3.1 PLL Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3.2 Receiver Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3.3 Transmitter Modulation Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3.4 Transmitter Amplifier Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

CHAPTER 4

ALIGNMENT

4.0 Required Test Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

4.1 Alignment Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

4.1.1 PLL Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

4.1.2 Transmitter Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

4.1.3 Receiver Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

CHAPTER 5

MAINTENANCE

5.0 Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

5.1 Periodic Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

5.2 Fuse Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

CHAPTER 6

DIAGRAMS AND PART LIST

6.0 PCB Layout and Part List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

CHAPTER 1

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DX 2547 SPECIFICATIONS

1.0 GENERAL

Model DX 2547 Frequency Range 26.965 – 27.405 MHz Emission Modes AM/USB/LSB Frequency Control Phase Lock Loop (PLL) synthesizer Frequency Tolerance 0.005 % Frequency Stability 0.001 % Operating Temperature Range Microphone Dynamic PTT, 500 Ω Input Voltage (DC/AC Selectable) 13.8V DC / 110V AC 60Hz Current Drain: Transmit (AM full mod.) < 3.5A Current Drain : Receiver (Squelched) (Max. audio output) < 1A Antenna Connector UHF; SO239

1.1 TRANSMITTER

RF Power Output AM : 4W ; SSB : 12W PEP RF Transmit Modes AM/SSB Modulation High and Low level Class B, Amplitude Modulation :

Spurious Emissions - 60dB Carrier Suppression - 60dB Audio Frequency Response 300 to 2500 Hz Antenna Impedance 50 Ohms Output Indicators Meter shows relative signal strength, RF output

1.2 RECEIVER

Sensitivity For 10dB S/N (AM/ SSB) IF Frequency AM: 10.695 MHz 1st IF, 455 KHz 2nd IF Image Rejection - 50dB Adjacent Channel Selectivity - 60dB RF Gain Control 45dB adjustable for optimum signal reception Automatic Gain Control (AGC) Figure Of Merit 100mV for 10dB Change in Audio Output Squelch Noise Blanker RF type Audio Output Power 2.5W @ 10% THD Audio Frequency Response 300 to 2500 Hz Built-in Speaker 8 Ohms, 4 Watts External Speaker (Not Supplied) 8 Ohms, 4 Watts

(SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE)

DX 2547

-30°C to +50°C

≤ 0.5A

AM and SSB.

power, SWR and AM Modulation level. Transmit LED glows red when transmitter is in operation.

< 0.5µV / < 0.15µV

Adjustable; threshold less than 0.5µV

CHAPTER 2

OPERATION

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POWER

TALKBACK

MOD

PWR

AM / SSB Base Station CB Radio

OFF

PHONES

RF POWER

MIC

MIC RF

20%

SWR

60%

40%

1.5

MOD

DIM TONE

+20

+40

80%

100%

MAX

DX 2547

PWR

+60

R. B.

RX / TX

GNF R.B. PA AM

CHANNEL

SWR ALERT

USB

ANL

GNF

LSB

CLARIFIER

NORMAL 9

SQUELCH

VOLUME

OFF

Figure 2-1 Front Panel

2.0 INTRODUCTION

This section explains the basic operating procedures for the Galaxy DX 2547 Base Station transceiver.

2.1 CONTROL AND CONNECTIONS

2.1.1 FRONT PANEL

Refer to the above Figure 2-1 for the location of the following controls:

1. PHONE JACK

Used to connect headphones.

2. MICROPHONE JACK

Used to connect microphone supplied with your radio.

3. RF POWER CONTROL

This control allows the user to adjust RF power output.

4. RF GAIN CONTROL

This control is used to reduce the gain of the RF amplifier under strong signal conditions.

5. MIC GAIN CONTROL

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Adjusts the microphone gain in the transmit and PA mode. This controls the gain to the extent that full talk power is available several inches away from the microphone. In the Public Address (PA) mode, the control functions as the volume control.

6. SWR/MOD/PWR SWITCH

This switch controls the function of the meter during the transmit mode. In the “SWR” position, the meter indicates the Standing Wave Ratio (SWR) of your antenna. There are no adjustments because the SWR circuit in this radio calibrates itself automatically. When the switch is in the “MOD” position, the green scale on the meter indicates your percentage of modulation. It is the most accurate when testing at four watts output. This operates in AM only, not in SSB. When this switch is in “PWR” position, the meter indicates your power output.

7. TONE CONTROL

This controls changes tone quality in receive only. Rotating the knob clockwise increases treble, counter clockwise rotation increases bass.

8. DIMMER CONTROL

This knob controls the level of brightness for the meter lamp and the channel display.

9. PA SWITCH

When this switch is pressed in, your voice will be heard only if an external speaker has been plugged into the “PA.” jack on the back of the radio. The radio does not operate when you are in the “PA” mode.

10. ROGER BEEP SWITCH

When this switch is pressed in, the radio transmits an audio tone at the end of your transmission to indicate that transmission has ended. As a courtesy to others, use the Roger Beep only when necessary.

11. CHANNEL SELECTOR

This control is used to select a desired transmit and receive channel.

12. ANL SWITCH

When this switch is pressed in, the Automatic Noise Limiter is activated.

13. MODE SWITCH

This control allows you to select one of the following operating modes: USB, AM or LSB.

14. GNF SWITCH

When this switch is pressed in, the radio is in CB operation but the Galaxy Noise Filter is engaged. This is a special noise filter that de-emphasizes audio high frequency response in order to increase the signal-to-noise ratio of weak signals. While you will notice a dramatic reduction in the “rushing” sound when this filter is activated, it does not have much effect on the signal-to-noise ratio of strong signals. This filter works best in SSB mode and may cause AM receive to sound distorted.

15. CLARIFIER SWITCH

Pushing this switch turns the Clarifier on for receive tracking.

16. CLARIFIER CONTROL

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When activated, allows adjustment of the receive frequency above or below the channel frequency by up to 800Hz. Although this control is intended primarily to tune in SSB signals, it may be used to optimize AM signals as well.

17. CLARIFIER LED

This LED lights when the Clarifier control is activated.

18. NB SWITCH When this switch is pressed in, the Noise Blanker is activated. The Noise Blanker is very effective in eliminating repetitive impulse noise such as ignition interference.

19. VOLUME CONTROL

Turn clockwise to set the desired listening level.

20. SQUELCH CONTROL

This switch is used to eliminate background noise being heard through the receiver which can be disturbing when no signal is being received. To use this feature of your radio, gently turn the switch fully counterclockwise, and then turn clockwise until the background noise is just eliminated. Further clockwise rotation will increase the threshold level so that only strong signals will be heard.

21. TALKBACK CONTROL

Adjust this knob for desired volume of Talkback. This is used to monitor your own voice. For example, you could use this feature to compare different microphones.

22. POWER ON/OFF SWITCH

Push this switch to apply power to the unit.

23. FRONT PANEL METER

The Front Panel Meter allows the user to monitor incoming signal strength, RF output power, SWR and AM Modulation level.

24. TX/RX LED

This LED lights red during transmit and green during receive.

25. CHANNEL DISPLAY

The channel display indicates the current selected channel.

26. SWR ALERT LED

This LED lights red when your SWR is higher than about 3:1. This is not an exact indicator of 3:1 SWR, but it is an indication that you should check your SWR reading.

27. GNF LED

This LED lights red when the GNF is on.

28. R.B. LED

This LED lights red when the Roger Beep is on.

29. FREQUENCY COUNTER

This display indicates the frequency of the selected channel.

30. PA LED

This LED lights red when the radio is in the PA mode.

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31. ANL LED

This LED lights red when the ANL is on.

32. USB LED

This LED lights red when the radio is in the USB mode.

33. AM LED

This LED lights red when the radio is in the AM mode.

34. NB LED

This LED lights red when the NB is on.

35. LSB LED

This LED lights red when the radio is in the LSB mode.

36. CH9/NORMAL/CH19 SWITCH

This control allows you to select channel 9 or channel 19 instantly. When the switch is placed in the “NORMAL” position, the user is able to select a desired transmit and receive channel with the channel selector switch.

2.1.2 REAR PANEL

Figure 2-2 represents the location of the following connections:

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Figure 2-2 Rear Panel

1. AC POWER CORD

Connect to AC power outlet for AC main supply.

2. FUSE

Accommodates a fuse for AC input circuit protection. Use a 125V 2A fuse for replacement.

3. DC POWER

This accepts a 13.8V DC power cable with built-in 7A fuse. The power cord provided with the radio has a black and red wire. The black goes to negative and the red goes to positive.

4. AC/DC POWER SELECTOR

This control is used to select a desired power supply of AC power or DC power.

5. ANTENNA

This jack accepts 50 ohms coaxial cable with a PL-259 type connector.

6. PA

This jack is for PA operation. Before operating, you must first connect a PA speaker (8 ohms, 4W) to this jack.

7. EXT SP

This jack accepts a 4 to 8 ohm, 4 watt external speaker. When the external speaker is connected to this jack, the built-in speaker will be disabled.

2.1.3 FREQUENCY CHART

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CHANNEL CHANNEL FREQUENCY

(MHz)

CHANNEL CHANNEL FREQUENCY

(MHz)

1 26.965 21 27.215

2 26.975 22 27.225

3 26.985 23 27.255

4 27.005 24 27.235

5 27.015 25 27.245

6 27.025 26 27.265

7 27.035 27 27.275

8 27.055 28 27.285

9 27.065 29 27.295

10 27.075 30 27.305

11 27.085 31 27.315

12 27.105 32 27.325

13 27.115 33 27.335

14 27.125 34 27.345

15 27.135 35 27.355

16 27.155 36 27.365

17 27.165 37 27.375

18 27.175 38 27.385

19 27.185 39 27.395

20 27.205 40 27.405

2.2 MICROPHONE

The receiver and transmitter are controlled by the push-to-talk switch on the microphone. Press the switch and the transmitter is activated, release the switch to receive. When transmitting, hold the

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microphone two inches from your mouth and speak clearly in a normal voice. The radio comes complete with a low impedance (500 ohm) dynamic microphone.

2.3 OPERATION

2.3.1 PROCEDURE TO RECEIVE

1. Be sure that the power source, microphone and antenna are connected to the proper connectors before going to the next step.

2. Press the POWER switch to apply power to the radio.

3. Set the VOL to a comfortable listening level.

4. Set the MODE switch to the desired mode.

5. Listen to the background noise from the speaker. Turn the SQUELCH knob slowly clockwise until the noise just disappears. The SQUELCH is now properly adjusted. The receiver will remain quiet until a signal is actually received. Do not advance the control too far or some of weaker signals will not be heard.

6. Set the CHANNEL selector switch to the desired channel.

7. Set the RF GAIN control fully clockwise for maximum RF gain.

8. Adjust the CLARIFIER control to clarify the SSB signals or to optimize AM signals.

2.3.2 PROCEDURE TO TRANSMIT

1. Select the desired channel of transmission

2. Set the MIC GAIN control fully clockwise.

3. If the channel is clear, depress the push-to-talk switch on the microphone and speak in a normal voice.

2.4 ALTERNATE MICROPHONES AND INSTALLATION

For best results, the user should select a low impedance dynamic type microphone or a transistorized microphone. Transistorized type microphones have a low output impedance characteristic. The microphones must be provided with a four-lead cable. The audio conductor and its shielded lead

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comprise two of the leads. The third lead is for transmit control and the fourth is for receiving control. The microphone should provide the functions shown in the schematic below (Figure 2-3).

4 WIRE MIC CABLE

Pin Number Mic Cable Lead 1 Audio Shield 2 Audio Lead 3 Transmit Control 4 Receive Control

Figure 2-3 Your Transceiver Microphone Schematic

Figure 2-4 Microphone plug an pin numbers viewed from rear of pin receptacle.

CHAPTER 3

CIRCUIT

DX 2547

DESCRIPTION

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3.0 INTRODUCTION

This section explains the technical theory of operation for the Galaxy DX 2547 Base Station transceiver.

3.1 PLL CIRCUIT

The Phase Lock Loop (PLL) circuit is responsible for developing the receiver’s first local oscillator signal and the transmitter’s exciter signal. The PLL circuit consists primarily of IC2, IC3, Q25, Q29 and Q28. The PLL circuit is programmed by the rotary channel switch GPS-0501. The GPS-0501 communicates the correct binary data information to the programmable divider inside of IC3. IC3 then controls the VCO (Voltage Controlled Oscillator) to oscillate on the correct frequency. This signal is fed either into the receiver’s first mixer (for receive operation) or the transmitter’s mixer (for transmit operation).

3.2 RECEIVER CIRCUIT

The incoming RF signal comes into the radio via the antenna and into the front-end pre-amp, Q17. The RF signal is fed into the dual mosfet mixer circuit of Q18/Q19 and then into the AM/SSB IF section of the receiver (depending on the mode of operation). The signal is then detected by either the AM detector or product detector and then fed to the audio amplifier section of the receiver and finally out to the speaker.

3.3 TRANSMITTER MODULATION CIRCUIT

(i) The transmitter modulation circuit modulates the low-level RF signal from the PLL exciter circuit

with the user’s audio voice signal from the microphone. The audio from the microphone is then amplified and fed into the transmit amplifier circuit.

(ii) If the transceiver is in the AM mode, the AF Power amplifier modulates the last RF amplifier,

which produces a true amplitude modulated RF signal.

(iii) If the transceiver is in the SSB mode, the audio signal is mixed with the 10.6975MHz oscillator in

IC6.

3.4 TRANSMITTER AMPLIFIER CIRCUIT

The transmitter takes the basic exciter signal from the TX mixer and amplifies it through a series of amplifiers consisting of Q52, Q51, Q49 and Q47 where it is then sent out to the antenna connector.

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CHAPTER 4

DX 2547

ALIGNMENT

4.0 REQUIRED TEST EQUIPMENT

DC Power Supply (13.8VDC, 10A)

RF Wattmeter (100 MHz, 50W)

Multimeter (Digital)

Automatic Modulation Meter

Audio Signal Generator

Frequency Counter (100 MHz)

RF Signal Generator (100 MHz)

Automatic Distortion Meter

Oscilloscope (50 MHz)

Sinad Meter

4.1 ALIGNMENT PROCEDURES

This transceiver has been aligned at the factory and does not require any adjustments at installation. The required test equipment listed is used for the test setup or alignment shown in Figure 4-1 Transmitter Test Setup and Figure 4-2 Receiver Test Setup. This test setup is used in part or total during the following adjustments. Refer to Page 43 for adjustment location.

4.1.1 PLL ALIGNMENT

ITEM U.U.T. SETTING ADJUST

MEASUREMENT

POINT

Regulator Voltage

VCO Disconnect ‘short PCB’ from TP7, TP8 and TP9.

Set CLARIFIER Control to 12 o’clock.

Connect Frequency Counter to IC3 Pin 8. VC1

AM Frequency Set radio to CH 1 AM RX mode.

USB Frequency Set radio to CH 1 USB RX mode.

LSB Frequency Set radio to CH 1 LSB RX mode.

TX Offset Frequency

AM OSC Set radio to CH 1 AM TX mode.

USB OSC Set radio to CH 1 USB TX mode.

LSB OSC Set radio to CH 1 LSB TX mode.

Connect Voltmeter positive lead to power switch. Connect Voltmeter negative lead to PCB ground. VR701

Set radio to CH 1 AM RX mode. Connect Voltmeter to TP2.

L14

Connect Oscilloscope to TP3.

L15

Connect Frequency Counter to TP3.

L20

Connect Frequency Counter to TP3.

L21

Connect Frequency Counter to TP3.

Set radio to CH 1 AM TX mode. Connect Frequency Counter to TP3.

L22

VR7

Connect Frequency Counter to TP5.

L23

Connect Frequency Counter to TP6.

L24

Connect Frequency Counter to TP6.

L25

13.8 VDC

2.5 VDC ± 0.1

Adjust for max.

10.2400MHz ± 20Hz

16.2700MHz ± 20Hz

16.2725MHz ± 20Hz

16.2675MHz ± 20Hz

10.6950MHz ± 10Hz

10.6925MHz ± 10Hz

10.6975MHz ± 10Hz

4.1.2 TRANSMITTER ALIGNMENT

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Galaxy dx2547 Service Manual

Specifications and Main Features

Frequently Asked Questions

User Manual