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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 installations 
is from the generator and ignition system in the vehicle. Under most operating 
conditions, 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 same installations 

ignition interference may be high enough to make good communications 
impossible. The electrical noise may come from several sources. Many possibilities 
exist and 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, the loaded whips do not present the problems 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 distance. A standard antenna connector (type SO239) 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 a 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.  

 
 

 
 
 
 
 
 
 

 

 
 
 

 
 
 
 
 
 
If you are 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 on your car (keeping in mind the radiation 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 light posts, fences, etc.). 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 

THE PROPER SETTING IS ACHIEVED WHEN THE SWR IS 
1.5 OR BELOW, AND WHEN IT HAS THE SAME READING 
FOR CHANNELS LOW BAND A1 AND HI BAND D40. 

 

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. 

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NOTE 

- 6 - 

NOTE 

Summary of Contents for DX-33HP

Page 1: ...p www cbtricks com Printed In Malaysia AT1148010H DX 33HP 10 Meter Amateur Mobile Transceiver OWNER S MANUAL POWER RX TX BAND D A E B F C MED MIC RF VOL SQ OFF AM FM PA HI LO NB ANL OFF LO HI OFF ECHO...

Page 2: ...ophone Plug in dynamic with push to talk switch and coiled cord Input Voltage Current 13 8V DC nominal 15 9V max 11 7V min Positive or negative ground Transmit AM FM Hi Power _ 10A Receiver Squelched...

Page 3: ...ood electrical 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 m...

Page 4: ...irection 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 distance A standard...

Page 5: ...ver 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 or ambient b...

Page 6: ...witch is placed in the ANL NB position the RF Noise Blanker is also activated The RF Noise Blanker is very effective for repetitive impulse noise such as ignition interference 13 BAND SWITCH HI LOW Th...

Page 7: ...gain OPERATING 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 microphon...

Page 8: ...the microphone jack is used to hold the pin receptacle during the soldering operation best results are obtained when the connections to pins 1 and 3 are made first and then the connections to pins 2...

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