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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.  

 
 

 
 
 

 
 
 
 
 
 
 

TUNNING THE ANTENNA FOR OPTIMUM SWR 

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 all 40 channels of the transceiver. Channel 1 
requires a longer antenna than Channel 40 because it is lower in frequency. Due to 
the various methods of adjusting antennas for proper SWR we have chosen what 
we think is the optimum method: 

 

A.  Antennas with adjustment screws (set screws)   

1.  Start with the antenna extended and tightens 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 21. @ Low band D or Hi band A. Press the 

PTT (push-to-talk) switch, and tap the antenna (making it shorter). The SWR 
meter will show a lower reading each time the antenna is tapped. By 
continuing to shorten the antenna you will notice the SWR reading will reach a 
low print and then start riding again. This means that you have passed the 
optimum point for Channel 21. Extend the antenna a short distance and again 
follow the procedure above. 
When the lowest point has been reached, switch to Channel 1 @ Low band A 
or Hi band E and then to Channel 40 @ Low band D or Hi band H and 
compare SWR 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 one it is cut, it can no 

longer be lengthed. 

 

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

piece off with pliers. 

 

 
 
 
 
 
 
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). 

 

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. 

NOTE 

- 5 - 

- 6 - 

Содержание DX 44V

Страница 1: ...rks on your radio to locate your problem Intermittent problems are easily overlooked so be sure to give as much detail as possible in your note Also please include your telephone number in case our technicians have any additional questions Do not send your power cord or microphone unless we ask for these items during our telephone conversation You are responsible for getting the radio safely to us...

Страница 2: ...ange 30 C to 50 C Microphone Plug in dynamic with push to talk switch and coiled cord Input Voltage 13 8V DC nominal 15 9V max 11 7V min Positive or negative ground Transmit AM full mod 2 2A Receiver Squelched 0 3A Maximum Audio output 0 7A Size 2 3 8 H x 7 7 8 W x 9 1 4 D Weight 5 Ibs Antenna Connector UHF SO239 Meter Illuminated indicates relative output power received signal strength TRANSMITTE...

Страница 3: ...ide a good 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 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 inter...

Страница 4: ...onsult your dealer for information regarding an adequate grounding system and prevention of electrolysis between fittings in the hull and water TUNNING THE ANTENNA FOR OPTIMUM SWR 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 fr...

Страница 5: ...d 2 SQUELCH outer dual concentric This control is used to cut off 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 or ambient backgrounds noise is eliminated Turn fully counterclockwise then slowly clockwise until the receiver noise disappears...

Страница 6: ...e frequency is shifted 10KHz up On following channels A channel can be used by setting this switch to 10KHz position Normal 10KHz 3 3A 7 7A 11 11A 15 15A 19 19A 14 OFF ANL NB When the switch is placed in the ANL NB position the RF noise blanker also is activated The RF noise blanker is very effective for repetitive impulse noise such as ignition interference 15 RECEIVER TRANSMIT INDICATOR The rece...

Страница 7: ...F 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 microphone and speak in a normal voice ALTERNATE MICROPHONES AND INSTALLATION For best results the user should select a low impedance dynamic type microphone or a transistorized microphone Transistorized type...

Страница 8: ...f 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 and 4 Use a minimum amount of solder and be careful to prevent excessive solder accumulation on pins which could cause a short between the pin and the microphone plug housing 6 When all soldering con...

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