Galaxy dx939 User Manual

PAGE

CHAPTER 1

Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

CHAPTER 2

DX-939

Installation

Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Mounting The Radio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Ignition Noise Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Tuning The Antenna For Optimum SWR . . . . . . . . . . . . . . . . . . . . . . . . . . 5

External Speaker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Public Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

CHAPTER 3

Operation

Control Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Front Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Solid State Citizens Band

Rear Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Frequency Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Procedure to Receive and Transmit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

TABLE OF CONTENTS

AM Mobile Transceiver

With Blue Illuminated Lite

OWNERS MANUAL

Receiving SSB Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Alternate Microphone and Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Maintenance And Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

A Few Rules That Should Be Obeyed . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

How Your CB Can Serve You . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Use Channel 9 For Emergency Message Only . . . . . . . . . . . . . . . . . . . . . . 20

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CHAPTER 1 SPECIFICATIONS

GENERAL

Model
Channels 40
Frequency Range 26.965 ~ 27.405 MHz
Emission AM
Frequency Control Phase-Lock-loop (PLL) Synthesizer
Frequency Stability 0.001%
Temperature Range
Input Voltage 13.8 VDC
Antenna Impedance 50 Ohms
Speaker Impedance 8 Ohms
Size 7 7/8” (W) x 9 1/4” (D) x 2 1/8” (H)
Weight 5.5 lbs.

TRANSMITTER

RF Power Output AM : 4W
Frequency Response 300 to 2500 Hz
Frequency Tolerance 0.005%
Spurious Emission Better Than -55 dB
Unwanted Sideband Better Than -55 dB

RECEIVER

Sensitivity for 10 dB (S+N)/N
Squelch Sensitivity Less Than 0.5 uV
Audio Power Output 2W @ 10% Distortion
Image Rejection Ratio -65 dB
AGC Figure of Merit 100 mV for 10dB Change in Audio Output
Audio Response 300 to 2500 Hz
Clarifier Range

(SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE)

DX-939

-30°C to +50°C

AM : 0.5 uV

± 1.0 KHz

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CHAPTER 2 INSTALLATION

LOCATION

Plan the location of the transceiver and microphone bracket before starting the
installation. Select a location that is convenient for operation and do es not interfere
with the driver or passengers. In automobiles, the transceiver is usually mounted
the dash panel with the microphone bracket beside it.

MOUNTING THE RADIO

The transceiver is supplied with a universal mounting bracket. When mounting
the bracket and radio to your car, make sure it is mechanically strong. Also, provide
a good electrical grounding connection to the chassis of the vehicle. Proceed as
follows to mount the transceiver:

1. After you have determined the most convenient location in your vehicle, hold

the transceiver with mounting bracket in the exact location desired. If nothing
will interfere with mounting it in the desired position, remove the mounting
bolts. Before drilling the holes, make sure nothing will interfere with the
installation of the mounting bolts.

2. Connect the antenna cable plug to the standard receptacle on the rear panel.

Most transceiver antennas are terminated with a type PL-259 plug and mate
with the ANT receptacle.

3. Connect the red DC power input wire (with the fuse) to +13.8V DC. This wire

extends from the rear panel. In automobile installation, +13.8V DC is usually
obtained from the accessory contact on the ignition switch. This prevent the set
being left on accidentally when the driver leaves the car and also permits
operating the unit without the engine running. Locate the accessory contact on
most ignition switches by tracing the power wire from the AM broadcast
receiver in the car.

4. Connect the black lead to –13.8V DC. This is usually the chassis of the car.

Any convenient location with good electrical contact (remove paint) may be
used.

5. Mount the microphone bracket on the right side of the transceiver or near the

transceiver, using two screws supplied. When mounting in an automobile,
place the bracket under the dash so that microphone is readily accessible.

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IGNITION NOISE INTERFERENCE

Use of a mobile receiver at low signal levels is normally limited by the presence
of electrical noise. The primary source of noise in automobile installation is from
the generator and ignition system in the vehicle. Under most operating condition s,
when signal level is adequate, the background noise does not present a serious
problem. Also, when extremely low level signals are being received, the transceiver
may be operated with vehicle engine turned off. The unit requires very little current
and therefore will not significantly discharge the vehicle battery.

Even though the transceiver has ANL and NB controls, in some installations
ignition interference may be high enough to make good communications
impossible. The electrical noise may come from several sources. Many possibilities
exist as variations between vehicles require different solutions to reduce the noise.

ANTENNA

A vertically polarized, quarter-wavelength whip antenna provides the most
reliable operation and greatest range. Shorter, loaded-type whip antennas are more
attractive, compact and adequate for applications where the maximum possible
distance is not required. Also, loaded whips do not present the prob lems of height
imposed by a full quarter-wavelength whip.

Mobile whip antennas utilize the metal body of the vehicle as a ground plane.
When mounted at a corner of the vehicle they are slightly directional, in the
direction of the body of the vehicle. For all practical purpose, however, the
radiation pattern is nondirectional. The slight directional characteristic will be
observed only at extreme distances. A standard antenna connector (type SO-239) is
provided on the transceiver for easy connection to a standard PL-259 cable
termination.

If the transceiver is not mounted on a metal surface, it is necessary to run a
separate ground wire from the unit to good metal electrical ground in the vehicle.
When installed in a boat, the transceiver will not operate at maximum efficiency
without a ground plate, unless the vessel has a steel hull.

Before installing the transceiver in a boat, consult your dealer for information
regarding an adequate grounding system and prevention of electrolysis between
fittings in the hull and water.

TUNING THE ANTENNA FOR OPTIMUM S.W.R

Since there is such a wide variety of base and mobile antennas, this section will

strictly concern itself to the various types of mobile adjustable antennas.

Because the antenna length is directly related to the channel frequency, it must be
tuned to resonate optimally on all channels of the transceiver. Channel 1 requires a
longer antenna than Channel 40 because it is a lower frequency.

Due to the various methods of adjusting antennas for proper S.W.R., we have
chosen what we think is the optimum method:

A. Antenna with adjustment screws (set screws).

1. Start with the antenna extended and tighten the set screw lightly enough so that

the antenna can be lightly tapped with your finger for easy adjustment.

2. Set your transceiver to Channel 20. Press the PTT (push-to-talk) switch, and

tap the antenna (making it shorter). The S.W.R meter will show a lower
reading each time the antenna is tapped. By continuing to shorten the antenna,
you will notice the S.W.R reading will reach a low point and then start rising
again. This means that you have passed the optimum point for Channel 20.

Extend the antenna a short distance and again follow the procedure ab ove. When
the lowest point has been reached, switch to Channel 1 an d then to Channel 40 and
compare S.W.R readings. They should be almost equal.

B. Antennas which must be cut to proper length

1. Follow the same procedure as above, but adjust the length by cutting in 1/8”

increments until a good match is obtained.

2. Be very careful not to cut too much at one time, as once it is cut, it can no

longer be lengthened.

3. The whip is easily cut by filing a notch all the way around and breaking the

piece off with pliers.

NOTE

The proper setting is achieved when the SWR is 1.5 or
below, and when it has the same reading for channels 1
and 40.

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If you’re having difficulties in adjusting your antenna, check the following:
a. All doors must be closed when adjusting the antenna

b. Make sure the antenna base is grounded.
c. Check your coaxial cable routing (it may be pinched when routed into the car)
d. Try a different location in your car (keeping in mind the radiatio n pattern you

wish.)

e. Is the antenna perfectly vertical?
f. Try a different location in your neighborhood. Stay away from large metal

objects when adjusting (metal telephone or lamp post, fences, etc.)

NOTE

The transceiver will operate into an SWR of 2 to 1
indefinitely and sustain an SWR of 20 : 1 for a maximum
of 5 minutes at rated operating conditions.

EXTERNAL SPEAKER

The external speaker jack (EXT SP.) on the rear panel is used for remote receiver
monitoring. The external speaker should have 8 ohms impedance and be able to
handle at least 4 watts. When the external speaker is plugged in, the internal
speaker is disconnected.

PUBLIC ADDRESS

To use the transceiver as a public address system, connect an external 8 ohms
speaker ( 4 watts minimum) t o the PA. SP. jack located on the rear panel. Direct
speaker away from the microphone to prevent acoustic feedback. Physical
separation or isolation of the microphone and speaker is important when operating
the PA at high output levels.

CHAPTER 3 OPERATION

CONTROL FUNCTIONS
FRONT PANEL

1. ON/OFF VOLUME CONTROL : Turn clockwise to apply power to the radio

and to set the desired listening level.

2. SQUELCH CONTROL : This control is used to control or eliminate receiver

background noise in the absence of an incoming signal. For maximum receiver
sensitivity, it is desired that the control be adjusted only to the point where the
receiver background noise is eliminated. Turn fully counter-clockwise, then
slowly clockwise until the receiver noise disappears. Any signal to be received
must now be slightly stronger than the average received noise. Further
clockwise rotation will increase the threshold level which a signal must
overcome in order to be heard. Only strong signals will be heard at maximum
clockwise setting.

3. MIC GAIN CONTOR : Adjusts the microphone gain in the transmit and PA

modes. 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.

4. RF GAIN CONTROL : This control is used to reduce the gain of the receive

amplifier under strong signal conditions.

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