Cobra Electronics 148.GTL.ST Two
Contents
1. Description Part No Cost Ea X Qty Amount Replacement microphone with 4 pin connector for 148 GTL ST CA 73 19 95 MOBILE POWER MICROPHONE Amplified Power Microphone with 4 pin connector for 148 GTL ST CA 75 19 95 NOISE CANCEL MICROPHONE for 148 GTL ST CA 77 39 95 ECHO POWER MICROPHONE or 148 GTL ST CA 79 69 95 High Performance Magnetic Mount Antenna Spring Base Tunable and 1 000 watt Capacity ATW 400 39 95 DC POWER CORD Exact replacement power cord for 148 GTL ST 426 011 N 001 7 50 MOUNTING BRACKET Replacement for 148 GTL ST 250 044 N 001 4 50 MOUNTING BRACKET SCREWS for 148 GTL ST 634 188 9 001 25 ea Prices subject to change without notice Illinois residents add 7 Cook Co residents add 75 7 75 total Amount Chicago residents add 196 8 7596 total ndiana residents add 596 Michigan residents add 4 Minnesota residents add 696 Ohio residents add 6 Wisconsin residents add 5 Tax if applicable Shipping handling 3 75 Total If you wish you can order directly from Cobra O rder by phone Call 1 773 889 3087 Press 1 from the main menu 8a m 8p m M F CST Order by mail or fax Please fill out order form below and mail fax directly to Cobra Mail to Cobra Accessories D ept 6500 W Cortland St Chicago IL 60707 Fax to 1 773 622 2269 Please print clearly Name Address Not P O Box City State Zip Telephone No Credit Card No Exp D2. 18 How SoundTracker Works sssss meme 19 Activating Testing Sound Tracker 20 Section VI Appendix nennen 22 23 eate tice tetro deba eee er 21 A few Rules That Should Be Obeyed 22 How Your Can Serve YOu 22 Use Channel 9 for Emergency M essages 23 Warranty Service Instructions sssssss 24 Limited Two Year Warranty sese ens 25 Cobra CB Radio Accessories 26 E The CB Story The Citizens Band lies between the shortwave broadcast and 10 meter Amateur radio bands and was established by law in 1949 The Class D two way communi cations service was opened in 1959 CB also includes a Class A citizens band and Class C remote control frequencies FCC regulations permit only transmissions one party to another rather than broadcasts to a wide audience Thus advertising is not allowed on CB Channels because that is broadcasting Cuts Static coming in adds Punch going out Cobra proudly introduces the first Patent Pending technology that dramatically improves the transmission and reception of CB radio signals This revolutionary system reconfigures the transmission signal which allows it to be transferre
3. 1 Press the SoundTracker button on the right side of front panel TESTING SOUNDTRACKER 1 Select any unused channel on your CB 2 Open the squelch fully by turning the knob counter clockwise until it stops 3 Turn the volume up louder than your nor mal listening level 4 Switch the SoundTracker toggle off and on Notice the significant reduction in noise 20 Code 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 10 9 10 10 10 11 10 12 10 13 10 16 10 17 10 18 10 19 10 20 10 21 10 22 10 23 10 24 10 25 10 26 10 27 10 28 10 29 10 30 10 32 10 33 10 34 10 35 10 CODE Meaning Code Receiving poorly 10 36 Receiving well 10 37 Stop transmitting 10 38 OK message received 10 39 Relay message 10 41 Busy stand by 10 42 Out of service leaving air 10 43 In service subject to call 10 44 Repeat message 10 45 Transmission completed standing by 10 50 Talking too rapidly 10 60 Visitors present Advise Weather Road condi 10 62 tions 10 63 Make pick up at 10 64 Urgent business 10 65 Anything for us Nothing for you return to 10 67 base 10 70 My location is 10 71 Call by telephone Reportin person to 10 77 Stand by 10 81 Completed last assignment 10 82 Can you contact 10 84 Disregard last information 10 85 am moving to channel 10 91 Identify your station 10 93 Time is up for contact Does not conform to FCC rules 10 94 will give you a radio che
4. Continued Thus when a voice is used in place of a whistle or tone in the proper listening mode the voice will be recei ved correctly whereas in the incorrect mode the voice will be translated backwards and cannot be made intelligible by the voice lock control When listening to an AM transmission a correct sideband is heard in either mode since both upper and lower sideband are received o nce the desired SSB mode has been selected frequency adjustment may be nec ssary in order to make the incoming signal intelligible the VO ICE LOCK control lows the operator to vary frequency above and below the exact center frequency f the received signal If the sound of the incoming signal is high or low pitched djust the operation of the VOICE LO CK Consider it as performing the same func on as a phonograph speed control When the speed is set too high voices will be igh pitched and if set too low voices will be low pitched Also there is only one correct speed that will make a particular record produce the same sound that was recorded If the record is played on a turntable that rotates in the wrong direction opposite sideband no amount of speed control VO ICE LO CK will produce an intelligible sound AM signal received while listening in one of SSB modes will produce steady tone carrier in addition to the intelligence unless the SSB receiver is tuned to exactly the same frequency by the VOICE LOCK co
5. purposes however the radia tion 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 sepa rate 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 re garding an adequate grounding system and prevention of electrolysis between fit tings in the hull and water Section III Installation Continued TUNING 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 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 a lower 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 adjustable screws set screws 1 Start with the antenna extended and tight
6. sure that the housing and the knurled ring of Fig 3 are pushed back onto the microphone cable before starting to solder If the washer is not captive to the pin receptacle body make sure that itis placed on the threaded portion of the pin receptacle body before soldering If the microphone jack is used to hold the pin receptacle during soldering opera tion 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 W hen all soldering connections to the pins of the microphone are com plete push the knurled ring and the housing forward and screw the housing onto the threaded portion of the pin receptacle body Note the location of the screw clearance hole in the plug housing with respect to the threaded hole in the pin receptacle body When the housing is completely threaded into the pin receptacle body a final fraction of a turn either clockwise or counterclockwise may be required to align the screw hole with the threaded hole in the pin receptacle body When these are aligned the retaining screw is then screwed into place to secure the housing to the pin receptacle body The two cable clamp retainer screws should now be tightened to secure the housing to the microphone cord If the cutting directions have bee
7. unit is in warranty upon receipt of your unit it will either be repaired or exchanged depending on the model Please allow approximately 3 to 4 weeks before contacting us for status If the unit is out of warranty a letter will auto matically be sent informing you of the repair charge or replacement charge If you have any questions please call 773 889 3087 for assistance For technical assistance please call our Automated Help Desk which can assist you by answering the most frequently asked questions about Cobra products 773 889 3087 24 hours a day 7 days a week A Consumer Service Representative can be reached through this same num ber 8 00 am 8 00 pm Monday through Friday CST Technical assistance is also available on line in the Frequently Asked Question FAQ section at www cobraelec com or by e mail to productinfo cobraelec com 24 LIMITED TWO YEAR WARRANTY CO BRA ELECTRONICS CORPORATION warrants that its CO BRA CB Radios and the component parts thereof will be free of defects in workmanship and materials for period of two 2 years from the date of first consumer purchase This warranty may be enforced by the first consumer purchaser provided that the product is uti lized within the U S A COBRA will without charge repair or replace at its option defective CB radios products or component parts upon delivery to the COBRA factory Service Department accompanied by proof of the date of first cons
8. 148 GTL ST MANUAL 10 1 98 10 56 AM Page 1 PRINTED IN THAILAND 0 Pus INSTRUCTIONS FOR YOUR Cobra 40 CHANNEL SOUND TRACKER N SYSTEM CITIZENS BAND SSB AM 2 W AY MOBILE RADIO Model 148 GTL ST Cobra Cobra Electronics Corporation POS 6500 W Cortland Street 748 T Chicago IL 60707 COBRA ELECTRONICS CORPORATION 1997 480 241 P 001 148 GTL ST MANUAL 10 1 98 10 56 AM Page 3 HC obra SSunpFrace R 40 CHANNEL CITIZENS BAND SSB AM 2 WAY MOBILE RADIO Model 148 GTL ST Contents Page The CB SoundTracker Story eene Section I Introduction eene Section II Specifications nennen 4 Section III Installation enne 6 7 8 Section IV D 17 Controls and Indicators eee 9 A Control Functions emen 9 10 11 B Indicator Functions ssssssee nemen 12 O perating Procedure to 12 perating Procedure to Transmit 13 Receiving SSB Signals sssse ns 13 14 Alternate Microphones and Installation 15 16 17 Section V Maintenance and Adjustment 18 21 FCG Warning eiie tette i dere d de Rd
9. 27 335 semiconductors 14 27 125 34 27 345 15 27 135 35 27 355 Meter 3 in 1 16 27 155 36 27 365 17 27 165 37 27 375 18 27 175 38 27 385 TRANSMITTER 19 27 185 39 27 395 Power Output 20 27 205 40 27 405 Modulation The COBRA 148 GTL ST has a vastly superior receiver which includes an RF gain control and noise blanker circuitry effective in both AM and SSB modes and an automatic noise limiter effective in the AM mode The receiver also features increased protection against cross modulation and strong adjacent channel signals To obtain maximum performance please read carefully the descriptions and oper ating instructions in this manual Intermodulation Distortion SSB Carrier Suppression Unwanted Sideband Frequency Response Serial No Output Impedance Date of Purchase O utput Indicators Dealer N ame Keep this manual for detailed information about your Cobra CB radio SAVEYO UR SALES RECEIPT THE CARTON AND PACKING MATERIALS FOR PO SSIBLE FUTURE USE 2 40 AM 40LSB 40 USB 26 965 to 27 405 MHz Phase Lock Loop PLL synthesizer 0 00596 0 001 30 C to 50 C Plug in dynamic with push to talk switch and coiled cord 13 8V DC nominal 15 9V max 11 7V min positive or negative ground Transmit AM full mod 2 2A SSB 12 watts PEP output 2A Receive Squelched 0 25A M aximum audio output 0 6A 2 3 g H x 7 7 8 x 9 1 4 D 5 Ibs UHF S0239 C 3 field effect transistors
10. 45 transistors 63 diodes 6 integrated circuits 1 two color light emitting diode Illuminated indicates relative output power received signal strength and SWR AM 4 watts SSB 12 watts PEP High and low level Class B Amplitude Modulation SSB 3rd order more than 25 dB 5th order more than 35 dB 55 dB 50 dB AM and SSB 300 to 2500 Hz 50 ohms unbalanced M eter shows relative RF output power and SWR Transmit LED glows red when transmitter is in operation 148 GTL ST MANUAL 10 1 98 10 56 AM Page 7 Section 11 Specifications Cont RECEIVER Sensitivity Selectivity Image Rejection IF Frequency Adjacent Channel Rejection AM and SSB RF Gain Control Automatic Gain Control AGC Squelch ANL Noise Blanker Voice Lock Range Audio Output Power Frequency Response Built in Speaker External Speaker N ot Supplied PA SYSTEM Power O utput External Speaker for PA Not Supplied SSB 0 25 uV for 10dB S N N at greater than 1 2 watt of audio output AM 0 5 uV for 10 dB S N y at greater than 1 2 watt of audio output AM 6dB 3 KHz 50 dB Q 9 KHz SSB 6 dB Q 1 1 KHz 60 dB Q 2 3 KHz More than 65 dB AM 7 8 MHz 1stIF 455 KHz 2nd IF SSB 7 8 MHz 60 dB AM amp 70 dB SSB 40 dB adjustable for optimum signal reception Less than 10 dB change in audio Section III Installation LOCATION Plan the location of the transcei ver and microphone brack
11. AL 10 1 98 10 56 AM Page 19 Section IV O peration Continued 1 8 STRIP amp TIN Fig 2 Microphone Cable Preparation To wire the microphone cable to the plug provided proceed as follows qe UP UA KNURLED RING HOUSING CABLE CLAMP RETAINER SCREWI2 RETAINING SCREW A MICROPHONE CONNECTOR ASSEMBLY WASHER B MICROPHONE CONNECTOR DISASSEMBLED FOR WIRING Fig 3 Microphone plug wiring Remove the retaining screw Unscrew the housing from the pin receptacle body Loosen the two cable clamp retainer screws Feed the microphone cable through the housing knurled ring and washer as shown Fig 3B The wires must now be soldered to the pins as indicated in the above wiring tables If a vise or clamping tool is available it should be used to hold the pin receptacle body during the soldering operation so that both hands are free to perform the soldering If a vise or clamping tool is not available the pin recep tacle body can be held in a stationary position by inserting it into the micro phone jack on the front panel The numbers of the pins of the microphone plug are shown in Fig 4 as viewed from the back of the plug Before soldering the wire to the pins pre tin the wire receptacle of each pin ofthe plug 16 E Section IV O peration Continued Fig 4 Microphone plug pin numbers viewed from rear of pin receptacle Be
12. Bring the sailboat into port Attention all motorists The Weather Bureau advises that the snow tomorrow will accumulate 4 to 6 inches There is a fire in the building on the corner of 6th and Main Streets This is Halloween patrol unit number 3 Everything is quiet here 23 148 GTL ST MANUAL 10 1 98 10 56 AM Page 27 If You Think You N eed Service If You Think You Need Service Call 773 889 3087 You may be asked to send your unit to the Cobra factory It will be necessary to furnish the following in order to have the product serviced and returned 1 For Warranty Repair include some form of proof of purchase such as a me chanical reproduction or carbon or a sales receipt If you send the original receipt it cannot be returned 2 Send the entire product Must include CB unit and microphone 3 Enclose a description of what is happening with the unit Include a typed or clearly printed name and address of where the unit is to be returned 4 Pack unit securely to prevent damage in transit If possible use the original pack ing material 5 Ship prepaid and insured by way of a traceable carrier to avoid loss in transit such as United Parcel Service UPS Roadway Parcel Service RPS or First Class Insured Mail to Cobra Factory Service Cobra Electronics Corporation 6500 W Cortland St Chicago IL 60707 Cobra is not responsible for units not received if package has not been properly insured 6 If the
13. ate Customer Signature CircleOne Visa MasterCard Discover Allow 4 to 6 weeks for deli very ffer valid in Continental U S only 26 NOTES
14. ck EM ERGEN CY TRAFFIC 10 99 Trouble at this station Confidential information 10 200 21 Section VI Appendix Citizens Band radio operators have largely adopted the 10 code for standard questions and answers Its use permits faster communications and better under standing in noisy areas The following table lists some of the more common codes and their meanings Meaning Correct time is W recker needed at Ambulance needed at Your message delivered Please turn to channel Traffic accident at Traffic Tie up at have a message for you All units within range please report Break channel W hat is the next message number Unable to copy use phone Net directed to Net clear Awaiting your next message assignment All units copy Fire at Proceed with transmission sequence Negative contact Reserve hotel room for Reserve room for My telephone number is My address is Talk closer to mike Check my frequency on this channel Please give me a long count Mission completed all units secure Police needed at 148 GTL ST MANUAL 10 1 98 10 56 AM Page 25 Section VI Appendix Continued A FEW RULES THAT SHOULD BE OBEYED 1 3 4 5 6 You are not allowed to carry on a conversation with another station for more than five minutes at a time without taking a one minute break to give others a chance to use the channel You are not allowed to blast others off the air by over powering them with illegally ampl
15. d The selected channel appears on the LED readout directly above the Channel Selector knob Channel 9 has been reserved by the FCC for emergency communications involving the immediate safety of life of individuals or immediate protection of property Channel 9 may also be used to render assistance to a motorist OFF ANL N B ANL SWITCH In the ANL position only the automatic noise limiter in the audio circuits is activated When the switch is placed in the ANL NB position the RF noise blanker also is activated The RF noise blanker is very effecti ve for repetitive impulse noise such as ignition interference 10 Section IV peration Continued 10 11 12 13 14 PA CB SWITCH Selects the mode of operation In the CB position the PA func tion is disabled and the unit will transmit and receive on the speaker that is con nected In the PA mode incoming CB transmission will be heard through the PA speaker This allows you to monitor messages while outside of your vehicle To use the PA feature a speaker having a voice coil impedance of 8 ohms and a power handling capability of at least three watts should be used This speak er must be plugged into the PA SPKR jack at the rear of the transceiver If the public address feature is to be used primarily for outdoor applications the use of a weatherproof horn type public address speaker is recommended The durability of this type speaker plus the inherent efficiency o
16. d more effectively through cluttered airwaves It literally punches your message through the hundreds of thousands of signals that are in the air At the same time SoundTracker system dynamically adjusts the relationship between the signal and static commonly referred to as noise This allows Cobra s SoundTracker system to significantly reduce the amount of static on all incoming CB signals The system can be further optimized when two SoundTracker CB s are used to talk to each other The end result is a clearer cleaner sounding reception of signals and more powerful transmissions which dramatically improve CB Communications All transmitter adjustments other than those supplied by the manufacturer as front panel operating controls must be made by or under the supervision of the holder of an FCC issued general Radio Telephone O perator s License Replacement or substitution of transistors regular diodes or other parts of a unique nature with parts other than those recommended by Cobra may cause violation of the technical regulations of Part 95 of the FCC Rules or violation of Type Acceptance requirements of Part 2 of the Rules You should read and understand Part 95 included with this unit of the FCC Rules and Regulations before operating your Cobra radio even though the FCC no longer requires you to obtain an operators license NOTICE Replacement or substitution of transistors regular diodes or other parts of a unique
17. d to comply with the communications act and with the rules of CB Radio Operation 18 s How SoundTracker Works SO U N DTRACKER SYSTEM W hile previous systems only blanked out or limited noise in higher sound fre quencies the revolutionary new SoundTracker System actually reduces noise while leaving the signal intact in the reception mode In the transmission mode it actually strengthens the signal providing you with a significant reduction in noise on reception and transmission Sound clarity is measured by the ratio of the signal level to the noise level The higher the signal to noise ratio the better the sound HOW SOUNDTRACKER WORKS Reception Cuts Noise Coming In With a normal CB distant signals fall below the squelch level and are unintelligi ble With a SoundTracker CB the noise level is cut by up to 9096 which increas es the signal to noise ratio and dramatically improves signal clarity This also allows you to significantly reduce the squelch level which greatly expands your listening range On Transmission Strengthens Signals G oing O ut A SoundTracker CB strengthens the transmit signal by more effectively using the available RF power output of the CB The result is improved transmission signal clarity and an expanded transmission range 19 148 GTL ST MANUAL 10 1 98 10 56 AM Page 23 On Activating Testing SoundTracker ACTIVATING SOUNDTRACKER
18. ed into the car 148 GTL ST MANUAL 10 1 98 10 56 AM Page 11 Section 111 Installation Continued Section IV O peration D Try a different location on your car keeping in mind the radiation pattern CONTROLS AND INDICATORS There are fourteen controls and four indicators on the front panel of your CO BRA 148 GTL ST you wish E Isthe antenna perfectly vertical F Try different location in your neighborhood Stay away from large metal objects when adjusting metal telephone or light posts fences etc NOTE The COBRA 148 GTL ST 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 SPK 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 W hen 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 ohm speaker 4 watts minimum to the PA SPK jack located on the rear panel Direct speaker away from the microphone to prevent acoustic feedback Physical separa A CONTROL FUNCTIONS i M microphone and speaker is important when operating the 1 OFF ON VOLUME inner concentric dial Turn clockwise to apply power to the unit and to s
19. een When in transmit the LED will be red 20 SOUNDTRACKER INDICATOR A red LED will illuminate when the SoundTracker system is engaged on your CB 21 PRESS TO TALK MICRO PHONE The receiver and transmitter are controlled by the Press To Talk switch on the microphone Press the switch and the transmitter is activated release the switch to recei ve When transmitting hold the microphone two inches from the mouth and speak clearly in a normal voice The radio comes complete with low impedance 500 ohm dynamic microphone For installation instructions on the other microphones see ALTERNATE MICROPHONES AND INSTALLATION section OPERATING PRO CEDURETO RECEIVE 1 Be sure that the power source microphone and antenna are connected to the proper connectors before going to the next step Set PA CB Switch to the CB position and turn unit on by turning VOL control clockwise on COBRA 148 GTL ST Set the VO LU M E for a comfortable listening level Set MODE switch to the desired mode Set the RF gain control fully clockwise for maximum RF gain Listen to the background noise from the speaker Turn the SQ U ELCH control slowly clockwise until the noise JUST disappears no signal should be pre sent Leave the control at this setting The SQ U ELCH is now properly adjust ed The receiver will remain quiet until a signal is actually received Do not advance the control too far or some of the weaker signals will not be heard 7 Setthe CHANNEL se
20. en the set screw lightly enough so that the antenna can be lightly tapped with your finger for easy adjustment 2 Set your COBRA 148 GTL ST to Channel 21 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 point and then start rising 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 and then to Channel 40 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 once 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 a pliers NOTE THE PROPER SETTING IS ACHIEVED WHEN THE SWRIS 1 5 OR BELOW AND WHEN IT HAS THE SAME READING FOR CHANNELS 1 AND 40 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 rout
21. er antenna output connector Select a channel near the middle of the band such as 21 or the channel you plan to use most frequently Turn the power on and set the meter function switch to the CAL position Press and hold the microphone push to talk button and using the SWR CAL control adjust the meter to read the CAL position indicated on the meter face Then without releasing the microphone button switch the meter function switch to the SWR position and read the SWR indicated The lower the figure the bet ter with 1 being ideal Generally speaking readings up to 3 are acceptable but over 3 indicates that you are losing radiated power and antenna adjust ment may be advisable DYNAMIKE 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 VOICELO CK Allows variation of the receiver operating frequencies above and below the assigned frequency Although this control is intended primarily to tune in SSB signals it may also be used to optimize AM signals as described in the O perating Procedure paragraphs DIM NOR BRT SWITCH Controls the brightness of the meter and LED chan nel indicator for optimum intensity for day or night time driving CHANNEL SELECTOR This switch selects any one of the forty Citizens Band or 80 single side band channels desire
22. er explanation of single sideband TONE SWITCH HI NOR LO W This switch is used to shape the audio response to the operator s preference Bass is increased in the LOW position and treble is increased in the HI position SOUNDTRACKER SWITCH Depressing this button turns on the SoundTracker system in your CB 11 148 GTL ST MANUAL 10 1 98 10 56 AM Page 15 Section IV O peration Continued B INDICATOR FUNCTIONS 15 S METER Swings proportionally to the strength of the incoming signal 16 RF METER Swings proportionally to the RF output power 17 SWR METER Swings proportionally to the ratio of standing wave voltage and RF output U sed to properly adjusts the length of the antenna and to monitor the qual ity of the coaxial cable and all RF electrical connections If there is any degradation whatsoever in any of the above due to humidity salt spray vibration or corrosion the SWR meter reading will rise thereby indicating that a problem exists To calibrate switch to the CAL position transmit in AM Mode by pressing the PTT mic switch and adjustthe SWR control to the CAL mark on the meter then switch to SWR position for the SW R measurement N ote CB must be in AM mode 18 CHANNEL INDICATOR Numbered LED indicates the selected channel you wish to operate on 19 RECEIVE TRANSMIT INDICATOR The receiver transmit LED indicator is located nextto the channel indicator When in receive the LED will be gr
23. et before starting the in stallation Select a location that is convenient for operation and does not interfere with the driver or passengers in the vehicle In automobiles the transceiver is usu ally mounted below the dash panel with the microphone bracket beside it MOUNTING THE CONNECTION The COBRA 148 GTL ST 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 connection to the chassis of the vehicle Proceed as follows to mount the transcei ver 1 output for inputs from 10 to 100 000 microvolts Adjustable threshold less than 0 25 uV Switchable RF type effective on AM and SSB 2 5 KHz 4 watts into 8 ohms 300 to 2500 Hz 4 ohms round 8 ohms disables internal speaker when connected 4 watts into external speaker 8 ohms SPECIFICATIONS SUBJECT TO CHANGEWITHOUT NOTICE After you have determined the most convenient location in your vehicle hold the COBRA 148 GTL ST 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 Connect the antenna cable plug to the standard receptacle on the rear panel Most CB antennas are terminated with a type PL 259 plug and mate with the receptacle Connect
24. et the desired listening level During normal CB operation the VOLUME control is used to adjust the output level obtained either at the transceiver speaker or the external speaker if used 2 SQUELCH outer concentric dial This control is used to cut off or eliminate receiver background noise in the absence of an incoming signal For maxi mum receiver sensitivity itis desired that the control be adjusted only to the point where the receiver background noise or ambient background noise is eliminated Turn fully counterclockwise then slowly clockwise until the receiv er noise disappears Any signal to be recei ved 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 a maximum clockwise setting 3 RF GAIN CONTROL inner concentric dial Used to reduce the gain of the RF amplifier under strong signal conditions 148 GTL ST MANUAL 10 1 98 10 56 AM Page 13 Section IV O peration Continued 4 SWR CAL CONTROL outer concentric dial In order for you to achieve maximum radiated power and the longest range it is important that your antenna be in good condition properly adjusted and matched to your trans ceiver The Built in SWR standing wave ratio meter lets you easily measure your antenna condition To operate this function connect your antenna to the transceiv
25. f such a speaker will provide more than adequate results when combined with the high audio output level available from the CO BRA 148 GTL ST With the PA speaker con nected as outlined previously be sure that there is physical separation between the microphone and the speaker itself If the speaker is located too close to the microphone acoustic feedback will result when the public address system is operated at high volume A directional type outdoor speaker reduces the amount of isolation required Some experimentation will deter mine the minimum amount of isolation required for a given sound level from the public address system NOTE PA volume is controlled by adjusting the DYNAM IKE knob to the desired volume S RF CAL SWR SWITCH When in the S RF position the meter swings propor tionally to the strength of the received signal W hen transmitting the meter indicates relative RF output power When in the CAL position the SWR meter can be calibrated by adjusting the SWR control to the CAL mark on the meter face When in SWR position the standing wave ratio is measured MODE USB AM LSB SWITCH This switch is used to select AM LSB or USB mode of operation Unless the station with which communication is desired is equipped with SSB the AM mode is normally used The mode selector switch changes the mode of operation of both transmitter and receiver simultaneous ly Turn to Receiving SSB signals for a furth
26. ified transmitter power or illegally high antennas You can t use the CB to promote illegal activities You are not allowed to use profanity You may not play music in your CB You may not use your CB to sell merchandise or professional service HOW YOUR CAN SERVE YOU Warn of traffic tie ups ahead Provide weather and road information Provide help fast in event of emergency or breakdown Suggest good spots to eat and sleep Make long trips more interesting and help keep you awake Provide direct contact with your office or home Make friends for you as you travel Provide local information to find your destination Help law enforcement officers by reporting drunk and reckless drivers 22 Section VI Appendix Continued USE CHANNEL 9 FOR EMERGENCY MESSAGES ONLY FCC gives the following examples of permitted and prohibited types of communi cations for use on Channel 9 These are guidelines and are not intended to be all inclusive Permitted Yes No Yes No Yes No Yes No Yes No Example M essage A tornado sighted six miles north of town This is observation post number 10 No tornado sighted am out of gas on Interstate 95 am out of gas in my driveway There is a four car collision at Exit 10 on the Beltway send police and ambulance Traffic is moving smoothly on the Beltway Base to Unit 1 the Weather Bureau has just issued a thun der storm warning
27. lector switch to the desired channel 8 Adjustthe VOICE LOCK control to clarify the SSB signals or to optimize AM signals 12 N t9 Section IV peration Continued OPERATING PROCEDURETO TRANSMIT 1 Select the desired channel of transmission Set the DYNAMIKE control fully clockwise 3 Ifthe channel is clear depress the Push To Talk switch on the microphone and speak in a normal voice RECEIVING SSB SIGNALS There are three types of signals presently used for communications in the Citizens Band AM USB and LSB When the MODE switch on your unit is placed in the AM position only standard double sideband full carrier signals will be detected An SSB signal may be recognized while in the AM mode by its characteristic Donald Duck sound and the inability of the AM detector to produce an intelligi ble output The USB and LSB modes will detect upper sideband and lower side band respectively and standard AM signals SSB reception differs from standard AM reception in that SSB receiver does not require a carrier or opposite sideband to produce an intelligible signal A single sideband transmitted signal consists only of the upper or the lower sideband and no carrier is transmitted The elimination of the carrier from the AM signal helps to eliminate the biggest cause of whistles and tones heard on channels which make even moderately strong AM signals unreadable Also SSB takes only half of an AM channel
28. n careful ly followed the cable clamp should secure to the insulation jacket of the microphone cable U pon completion of the microphone plug wiring connect and secure the microphone plug in the transcei ver 17 148 GTL ST MANUAL 10 1 98 10 56 AM Page 21 Section V Maintenance and Adjustment The COBRA 148 GTL ST transceiver is specifically designed for the environment encountered in mobile installations The use of all solid state circuitry and its light weight result in high reliability Should a failure occur however replace parts only with identical parts Do not substitute Refer to the schematic diagram and parts list NOTE If the performance described in the OPERATION and MAINTENANCE AND ADJUSTMENT sections is not obtained review the operating instructions to insure that proper procedures were followed If a problem still exists refer to WARRANTY SERVICE INSTRUCTIONS elsewhere in this manual FCC WARNING Replacement or substitution of transistors regular diodes or other parts of a unique nature with parts other than those recommended by Cobra may cause violation of the technical regulations of Part 95 of the FCC Rules or violation of Type Acceptance requirements of Part 2 of the Rules Citizens Band CB Radio operators are no longer required to obtain an FCC license to operate their CB equipment or provide station identification Nevertheless an operator of a CB radio station is still require
29. nature with parts other than those recommended by Cobra may cause violation of the technical regulations of Part 95 of the FCC Rules or violation of Type Acceptance requirements of Part 2 of the Rules Citizens Band CB Radio operators are no longer required to obtain an FCC license to operate their CB equipment or provide station identification An operator of a CB radio station is required to comply with the communications act and with the rules of CB Radio Operation 1 148 GTL ST MANUAL 10 1 98 10 56 AM Page 5 Section Introduction Section 11 Specifications FREQUENCY RANGE GENERAL The CO BRA 148 GTL ST transcei ver represents one of the most advanced SSB AM Channels two way radios ever designed for use as a Class D station in the Citizens Radio Frequency Range Service This unit features advanced Phase Lock Loop PLL circuitry which is used in the AM mode and in the upper and lower single sideband modes providing Frequency Control complete coverage of all 40 channels shown belo w Frequency Tolerance Channel Channel Frequency Channel Channel Frequency Frequency Stability in MHz in MHz O perating Temperature Range 1 26 965 21 27 215 Microphone 2 26 975 22 27 225 3 26 985 23 27 255 Input Voltage 4 27 005 24 27 235 5 27 015 25 27 245 Current Drain 6 27 025 26 27 265 7 27 035 27 27 215 8 27 005 28 27 285 9 27 065 29 27 295 Size 10 27 075 30 27 305 Weight b UE 2 Antenna Conductor 13 21115 33
30. ntrol For simplicity itis rec ommended that the AM modes be used to listen to AM signals 14 6 Section IV O peration Continued ALTERNATE MICRO PHONES AND INSTALLATION For best results the user should select a low impedance dynamic type micro phone or a transistorized microphone Transistorized type microphones have a low output impedance characteristic The microphones must be provided with a 4 lead cable The audio conductor and its shielded lead comprise two of the leads The third lead is for receive control the forth is for transmit control The microphone should provide the functions shown in schematic below 4 WIRE MIC CABLE Pin Number Mic Cable Lead 1 Grounding 2 Audio Lead 3 Transmit Control 4 Receive Control Fig 1 Cobra 148 GTL ST microphone schematic If the microphone to be used is provided with pre cut leads they must be revised as follows 1 Cut leads so that they extend 7 16 beyond the plastic insulating jacket of the microphone cable see Fig 2 2 All leads should be cut to the same length Strip the ends of each wire 1 8 and tin the exposed wire Before beginning the actual wiring read carefully the circuit and wiring informa tion provided with the microphone you select Use the minimum head required in soldering the connections Keep the exposed wire lengths to a minimum to avoid shorting when the microphone plug is reassembled 15 148 GTL ST MANU
31. t significantly discharge the vehicle battery Even though the COBRA 148 GTL ST has ANL and NB controls in some installa tions 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 Consult your COBRA dealer or a 2 way radio technician for help in locat ing and correcting the source of severe noise ANTENNA Since the maximum allowable power output of the transmitter is limited by the FCC the antenna is one important factor affecting transmission distance Only a properly matched antenna system will allow maximum power transfer from the 50 ohm transmission line to the radiating element In mobile installations cars trucks boats etc an antenna system that is non directional should be used A vertically polarized quarter wavelength whip antenna provides the most reliable operation and greatest range Shorter loaded type whip antennas are more attrac tive compact and adequate for applications where the maximum possible dis tance 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
32. 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 prevents 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 receiv er in the car Connectthe 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 Mount the microphone bracket on either side of the transceiver using the two screws supplied When mounting in an automobile place the bracket under the dash so the microphone is readily accessible 148 GTL ST MANUAL 10 1 98 10 56 AM Page 9 Section III Installation 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 transceiv er may be operated with vehicle engine turned off The unit requires very little current and therefore will no
33. therefore two SSB conversations will fit into each channel expanding the 40 AM channels to 80 SSB channels The reduction in channel space required also helps in the receiver because only half of the noise and interference can be received with 100 of the SSB signal An SSB signal may be received only when the listening receiver is functioning in the same mode In other words an upper sideband signal USB may be made intelligible only if the receiver is functioning in the USB position If a lower sideband LSB signal is heard when the receiver isin the USB mode no amount of tuning will make the signal intelligible The reason for this may be understood if you consider that when the modulation is applied to the transmit ter s microphone in the USB mode the transmitter s output frequency is increased whereas in the LSB mode the transmitter s output frequency is decreased The result in listening to the receiver is that when the MODE switch is in the proper position either U SB or LSB a true reproduction of single tone of modulation will result and if the tone is increased in frequency such as a low pitched whistle or a high pitched whistle you will hear the increase in the output tone of the receiver If the incorrect mode is selected an increase in tone of a whistle applied to the transmitter will cause a decrease in the resultant tone from the receiver 13 148 GTL ST MANUAL 10 1 98 10 56 AM Page 17 Section IV O peration
34. umer purchase such as a duplicated copy of a sales receipt You must pay any initial shipping charges required to ship the product for warranty service but the return charges will be at Cobra s expense if the product is repaired or replaced under warranty For further details concerning procedures for obtaining service see the If You Think You Need Service section of the Owner s M anual Exclusions This limited warranty does not apply 1 to any product damaged by accident 2 in the event of misuse or abuse of the product or as a result of unautho rized alterations or repairs 3 if the serial number has been altered defaced or re moved 4 if the owner of the product resides outside the U S A All implied warranties including warranties of merchantability and fitness for a particular purpose are limited in duration to the length of this warranty COBRA shall not be liable for any incidental consequential or other damag es including without limitation damages resulting from loss of use or cost of installation Some states do not allow limitations on how long an implied warranty lasts and or do not allow the exclusion or limitation of incidental or consequential damages so the above limitations may not apply to you COBRA ELECTRO NICS CORPO RATION 6500 W Cortland Street Chicago Illinois 60707 25 148 GTL ST MANUAL 10 1 98 10 56 AM Page 29 CO BRA CB RADIO ACCESSO RIES
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