Owner`s Manual - Buy Two Way Radios
Contents
1. Fig 2 Microphone Cable Preparation To wire the microphone cable to the plug provided proceed as follows KNURLED RING H HOUSING H 3 4 OO 2S 1 CABLE CLAMP RETAINER SCREW 2 RETAINING SCREW A MICROPHONE CONNECTOR ASSEMBLY WASHER Fig 3 Microphone plug wiring Remove the retaining screw Unscrew the housing from the pin receptacle body Loosen the two cable clamp retainer screws Pw NP Feed the microphone cable through the housing knurled ring and washer as shown Fig 3B 5 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 of the plug 16 Fig 4 Microphone plug pin numbers viewed from rear of pin receptacle Be 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 it is2. Cobra Accessories Dept 6500 W Cortland St Chicago IL 60707 Fax to 1 773 622 2269 Please print clearly Name Address Not P O Box City State LZ Credit Card No Exp Date Customer Signature Circle One Visa MasterCard Discover Allow 4 to 6 weeks for delivery Offer valid in Continental U S only HC obra Cobra Hectronics Corporation 6500 W Cortland Street Chicago IL 60707 PRINTED IN THAILAND COBRA ELECTRONICS CORPORATION 1996 001 480 163 P Al
3. 025 26 27 265 cal regulations of Part 95 of the FCC Rules or violation of 7 27 035 27 27 275 Type Acceptance requirements of Part 2 of the Rules 8 27 005 28 27 285 Citizens Band CB Radio operators are no longer required to 9 27 065 29 27 295 obtain an FCC license to operate their CB equipment or 10 27 075 30 27 305 provide station identification An operator of a CB radio station is required to comply 11 27 085 31 27 315 3 S 12 27 105 32 27 325 with the communications act and with the rules of CB 13 27 115 33 27 335 Radio Operation 14 27 125 34 27 345 15 27 135 35 27 355 16 27 155 36 27 365 Serial No 17 27 165 37 27 375 18 27 175 38 27 385 Date of Purchase 19 27 185 39 27 395 Dealer Name 20 27 205 40 27 405 Keep this manual for detailed information about your Cobra CB radio The COBRA 148GTL has a vastly superior receiver which includes an RF gain con trol and noise blanker circuitry effective in both AM and SSB modes and an auto matic noise limiter effective in the AM mode The receiver also features increased protection against cross modulation and strong adjacent channel signals SAVE YOUR SALES RECEIPT THE CARTON AND PACKING MATERIALS FOR POSSIBLE FUTURE USE To obtain madmum performance please read carefully the descriptions and oper ating instructions in this manual Section ll Specifications GENERAL Channels Frequency Range Frequency Control Frequency Tolerance Frequency Stability O pera
4. better under standing in noisy areas The following table lists some of the more common codes and their meanings 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 36 10 CODE Meaning Receiving poorly Receiving well Stop transmitting OK message received Relay message Busy stand by Out of service leaving air In service subject to call Repeat message Transmission completed standing by Talking too rapidly Visitors present Advise Weather Road conditions Make pick up at Urgent business Anything for us Nothing for you return to base My location is Call by telephone Report in person to Stand by Completed last assignment Can you contact Disregard last information am moving to channel Identify your station Time is up for contact Does not conform to FCC rules will give you a radio check EMERGENCY TRAFFIC Trouble at this station Confidential information Correct time is 19 Code Meaning 10 37 Wrecker needed at 10 38 Ambulance needed at 10 39 Your message delivered 10 41 Please tum to channel 10 42 Traffic accident at 10 43 Traffic Tie up at 10 44 have a message for you 10 45 All units within range please report 10 50 Break channel 10 60 What is the next message number 10 62 Unable to copy use phone 10
5. exactly the same frequency by the VOICE LOCK control For simplicity it is recommended that the AM modes be used to listen to AM signals 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 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 148GTL 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 Section IV Operation Continued
6. 63 Net directed to 10 64 Netclear 10 65 Awaiting your next message assi gnment 10 67 All units copy 10 70 Fire at 10 71 Proceed with transmission in sequence 10 77 Negative contact 10 81 Reserve hotel room for 10 82 Reserve room for 10 84 My telephone number is 10 85 My address is 10 91 Talk closer to mike 10 93 Check my frequency on this channel 10 94 Please give me a long count 10 99 Mission completed all units secure 10 200 Police needed at A FEW RULESTHAT SHOULD BE OBEYED 1 ANAW 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 overpowering them with illegally amplified 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 CB 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 enforc
7. 9 for Emergency Messages Only 21 Warranty Service lnsiruchHonme eee eeeeeeeeeeeeseeeneeseeeeeeeaes 22 Limited Two Year Warrantv ese eeaeeeeeeseeeaees 23 Cobra CB Radio Accesores 00 0 0 ccc cccc ccc cc ee eeeeeeeaes Inside Back Cover Section I Introduction The Citizens Band lies between the shortwave broadcast and 10 meter Amateur FREQUENCY RANGE radio bands and was established by law in 1949 The Class D two way communi The COBRA 148GTL transceiver represents one of the most advanced SSB AM two cations service was opened in 1959 CB also includes a Class A citizens band and way radios ever designed for use as a Class D station in the Citizens Radio Service Class C remote control frequencies This unit features advanced Phase Lock Loop PLL circuitry which is used in the AM FCC regulations permit only transmissions one party to another rather than mode and in the upper and lower single sideband modes providing complete cover broadcasts to a wide audience Thus advertising is not allowed on CB Channels age of all 40 channels shown below because that is broadcasting Channel Channel Frequency Channel Channel Frequency in MHz in MHz 1 26 965 21 27 215 2 26 975 22 27 225 NOTICE 3 26 985 23 27 255 Replacement or substitution of transistors regular diodes or 4 27 005 24 27 235 other parts of a unique nature with parts other than those 5 27 015 25 27 245 recommended by Cobra may cause violation of the techni 6 27
8. AL mark on the meter then switch to SWR postion for the SWR measurement Note CB must be in AM mode CHANNEL INDICATOR Numbered LED indicates the selected channel you wish to operate on RECEIVE TRANSMIT INDICATOR The receiver transmit LED indicator is located next to the channel indicator When in receive the LED will be green When in transmit the LED will be red PRESS TO TALK MICROPHONE 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 receive 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 PROCEDURETO RECEIVE 1 Au FW 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 tum unit on by turning VOL control clockwise on COBRA 148GTL Set the VOLUME 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 SQUELCH control slowly clockwise until the noise JUST disappears no signal should be pre sent Leave the contro
9. ARRANTY COBRA CB RADIO ACCESSORIES Description Part No Cost Ea X Qty Amount Replacement microphone with 4 pin connector for 148 GTL CA 73 19 95 COBRA ELECTRONICS CORPORATION warrants that its COBRA CB Radios and the component parts thereof will be free of defects in workmanship and materials Sege Geer EE for period of two 2 years from the date of first consumer purchase This warranty for 148 GTL CA 75 19 95 Has pier samen first consumer DUNE provided thatthe predict is tu NOISE CANCEL MICROPHONE for 148 GTL CA 77 39 95 s e gt ECHO POWER MICROPHONE or 148 GTL A 7 69 COBRA will without charge repair or replace at its option defective CB radios mhapa CROPHONE or 148 a Vide products or component parts upon delivery to the COBRA factory Service High Performance Magnetic Mount Antenna D Spring Base Tunable and 1 000 watt Capacity ATW 400 39 95 epartment accompanied by proof of the date of first consumer purchase such as a duplicated copy of a sales receipt DC POWER CORD Exact replacement power cord EE SE for 148GTL 426 011 N 001 7 50 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 MOUNTING BRACKET Replacement for 148GTL 250 044 N 001 4 50 or replaced under warranty For further details concerning procedures for obtaining MOUNTING BRACKET SCREWS service see the If You Think You N
10. L 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 LSB AM USB 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 simultaneously Tum to Receiving SSB signals for a further explanation of single sideband 13 TONE SWITCH HI NOR LOW 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 11 B INDICATOR FUNCTIONS S METER Swings proportionally to the strength of the incoming signal RF METER Swings proportionally to the RF output power SWR METER Swings proportionally to the ratio of sanding wave voltage and RF output Used 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 soray vibration or corrosion the SWR meter reading will rise thereby indicating that a problem exists To calibrate switch to the CAL position Darrin AM Mode by pressing the PTT mic switch and adjust the SWR control to the C
11. Lock Range Audio Output Power Frequency Response Built in Soeaker External Speaker Not Supplied PA SYSTEM Power Output External Speaker for PA Not Supplied SSB 0 25 LN for 10dB S N yN at greater than 1 2 watt of audio output AM 0 5 LN for 10 dB S N at greater than 1 2 watt of audio output AM 6dB 3 KHz 50 dB 9 KHz SSB 6 dB 1 1 KHz 60 dB 2 3 KHz More than 65 cB AM 7 8 MHz 1st IF 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 output for inputs from 10 to 100 000 microvolts Adjustable threshold less than 0 25 uV Switchable RF type effective on AM and SSB 42 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 CHANGE WITHOUT NOTICE 4 Section Ill ia r f tee LOCATION Plan the location of the transceiver and microphone bracket 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 148GTL is supplied with a universal mounting bracket When mount ing the bracket and radio to your car make sure it is mec
12. MUM 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 tighten the set screw lightly enough so that the antenna can be lightly tapped with your finger for easy adjustment 2 Set your COBRA 148GTL 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 anten na you will notice the SWR reading will reach a low point and then start ris ing 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
13. OPERATING INSTRUCTIONS FOR YOUR Sc obra 40 CHANNEL CITIZENS BAND SSB AM 2 WAY MOBILE RADIO Model 148 GTL 9 Eeer e i SEN SEI SS How To Use Your fe Cobra 40 CHANNEL CITIZENS BAND SSB AM 2 WAY MOBILE RADIO Mode 148 GTL Contents Page The e SO E 1 Section l INtOCUCTION 2 ee eee eeee essen KEE EE KKK KEE EES EE 2 Section Il SDeCCHPICATIONS een ee ee eee ene en eee EE EE EE eeneneneeeeeeeeeeeeees 3 4 Section TID Installation eene EE EEN EE KENE KEE EE EE EE KEEN NENNEN 5 6 7 8 Section IV Operation nn ccseeeeeeeeeneneneneneneeeeeenseenenenensneeneneneneneeenenes 9 17 Contr olsand Indicators vesser Steet CAE n EE AEE EE 9 ACONITOLFUNGH ONS eege EE ATE EAE 9 10 11 B lndicator FUNCHONS sssssssesssssrrsrrertrrtertrtertnttertnnnnnnttennnne rnent nenn 12 Operating Procedure to BeCeive nsec eeeeeeeeeeeeeeeeeeaeeeseeeaeens 12 Operating Procedure to Transmit cccccceeeeeeeceeeeeeeeeeseeeeeeeeeeeeeees 13 Receiving SSB Signals cceceeeeeeeeeeeee eee eeeeeeseeeeeesaeeseesaeeeaeed 13 14 Altemate Microphones and Installation cceeeeeeeeeeees 15 16 17 Section V Maintenance and Adjustment s 21 18 21 FOC WAITING EN 18 Ke CM DT E KE 19 20 21 VTA OCS EE 19 A few Rules That Should Be Obeyed ccccceceeeeeeeeeeeeeeeeeeeeeeeeenees 20 How Your CB Can Serve YOU ssicicsseneseceaeaves eu sneteseecaetenedvensusteeeeeneaede 20 Use Channel
14. Send the entire product Must include CB unit and microphone 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 retumed Pack unit securely to prevent damage in transit If possible use the original pack ing material 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 Hectronics Corporation 6500 W Cortland St Chicago IL 60707 Cobra is not responsible for units not received if package has not been properly insured If the 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 number 8 00 am 8 00 pm Monday through Friday CST E mail questions to productinfo cobraelec com 22 LIMITED TWO YEAR W
15. a 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 quarte wavelength whip Mobile whip antennas utilize the metal body of the vehicle as a ground plane When mounted at a comer of the vehicle they are slightly directional in the direction of the body of the vehicle For all practical 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 Ill Installaton Continued TUNING THE ANTENNA FOR OPTI
16. aker 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 speaker must be plugged into the PA SPKR jack at the rear of the transceiver If the pub lic 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 of such a speaker will provide more than adequate results when combined with the high audio output level available from the COBRA 148GTL With the PA speaker connected as out lined previously be sure that there is physical separation between the micro phone and the speaker itself If the speaker is located too close to the micro phone acoustic feedback will result when the public address system is operat ed at high volume A directional type outdoor speaker reduces the amount of isolation required Some experimentation will determine the minimum amount of isolation required for a given sound level from the public address system NOTE PA volume is controlled by adjusting the DYNAMIKE knob to the desired volume S RF CAL SNR SWITCH When in the SRF position the meter swings propor tionally to the strength of the received signal When transmitting the meter indi cates relative RF output power When in the CA
17. eed Service section of the Owner s Manual E EE tc 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 Illinois residents add 8 75 Indiana residents add 5 Michigan residents add 6 Ohio residents add 5 Wisconsin residents add 5 Amount Tax if applicable Shipping handling Total 3 50 If you wish you can order directly from Cobra Order by phone the above limitations may not apply to you 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 COBRA ELECTRONICS CORPORATION directly to Cobra 6500 W Cortland Street Chicago Illinois 60707 Mail to
18. ement officers by reporting drunk and reckless drivers 20 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 Example Message Yes A tornado sighted six miles north of town No This is observation post number 10 No tornado sighted Yes am out of gas on Interstate 95 No am out of gas in my driveway Yes There is a four car collision at Exit 10 on the Beltway send police and ambulance No Traffic is moving smoothly on the Beltway Yes Base to Unit 1 the Weather Bureau has just issued a thun der storm warning Bring the sailboat into port No Attention all motorists The Weather Bureau advises that the snow tomorrow will accumulate 4 to 6 inches Yes There is a fire in the building on the corner of 6th and Main Streets No This is Halloween patrol unit number 3 Everything is quiet here 21 If You Need 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 retumed 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 retumed
19. hanically strong Also provide a good electrical connection to the chassis of the vehicle Proceed as fol lows to mount the transceiver 1 After you have determined the most convenient location in your vehicle hold the COBRA 148GTL 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 CB antennas are terminated with a type PL 259 plug and mate with the 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 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 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 either side of the transceiver using the two screws supplied When mounting in an automobile place the bracket under the dash so
20. he transceiver 17 Section V Maintenance and Adjustment The COBRA 148GTL transceiver is specifically designed for the environment en countered 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 instru ctions 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 required to comply with the communications act and with the rules of CB Radio Operation 18 Citizens Band radio operators have largely adopted the 10 code for standard questions and answers Its use permits faster communications and
21. l at this setting The SQUELCH 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 Set the CHANNEL selector switch to the desired channel Adjust the VOICE LOCK control to clarify the SSB signals or to optimize AM signals 12 OPERATING PROCEDURE TO TRANSMIT 1 Select the desired channel of transmission 2 Set the DYNAMIKE control fully clockwise 3 If the channel is clear depress the Push To Talk switch on the microphone and speak in a normal voice RECHVING 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 elimi
22. match is obtained 2 Be very careful not to cut too much at one time as once itis 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 SWR IS 1 5 OR BELOW AND WHEN IT HASTHE 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 routed into the car 7 Section Ill Installaton Continued 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 NOTE The COBRA 148GTL 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 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 exte
23. nate 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 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 is in 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 USB 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 t
24. o the transmitter will cause a decrease in the resultant tone from the receiver 13 Thus when a voice is used in place of a whistle or tone in the proper listening mode the voice will be received 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 Once the desired SSB mode has been selected frequency adjustment may be necessary in order to make the incoming signal intelligible the VOICE LOCK con trol allows the operator to vary frequency above and below the exact center fre quency of the received signal If the sound of the incoming signal is high or low pitched adjust the operation of the VOICE LOCK Consider it as performing the same function as a phonograph speed control When the speed is set too high voices will be high 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 tumtable that rotates in the wrong direction opposite sideband no amount of speed control VOICE LOCK will produce an intelligible sound An AM signal received while listening in one of the SSB modes will produce a steady tone carrier in addition to the intelligence unless the SSB receiver is tuned to
25. 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 When all soldering connections to the pins of the microphone are complete 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 coun terclockwise 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 7 The two cable clamp retainer screws should now be tightened to secure the housing to the microphone cord If the cutting directions have been carefully followed the cable clamp should secure to the insulation jacket of the mi crophone cable 8 Upon completion of the microphone plug wiring connect and secure the microphone plug in t
26. rnal 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 tion or isolation of the microphone and speaker is important when operating the PA at high output levels Section IV Operation CONTROLS AND INDICATORS There are thirteen controls and three indicators on the front panel of your COBRA 148GTL Ze Cobra 148 att ob x Use a S CAL Non OFF em ise VOL gt SQ RF GAIN SWR DYNAMIKE VOICELOCK siv606 A CONTROL FUNCTIONS H LIT TU DIM NOR BRT 1 OFF ON VOLUME inner dual concentric Turn clockwise to apply power to the unit and to set 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 dual concentric This control is used to cut off or eliminate receiver background noise in the absence of an incoming signal For maxi mum receiver sensitivity it is 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 received must now be slightly stronger than the average received noise Further clockwise rotation will increase the threshold level which a signal mus
27. rophone In the Public Address PA mode the control functions as the volume control VOICE LOCK Allows variation of the receiver operating frequencies above and below the assigned frequency Although this control is intended primari ly to tune in SSB signals it may also be used to optimize AM signals as described in the Operating Procedure paragraphs DIM NOR BRT SWITCH Controls the brightness of the meter and LED channel indicator for optimum intensity for day or night time driving CHANNEL SELECTOR This switch selects any one of the forty Citizens Band channels desired 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 indi viduals or immediate protection of property Channel 9 may also be used to render assistance to a motorist OFF ANL NB 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 effective for repetitive impulse noise such as ignition interference 10 10 11 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 spe
28. t overcome in order to be heard Only strong signals will be heard at a maximum clockwise setting 3 RF GAIN CONTROL inner dual concentric Used to reduce the gain of the RF amplifier under strong signal conditions 4 SWR CAL CONTROL outer dual concentric 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 transceiver 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 con trol 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 fig ure the better with 1 being ideal Generally speaking readings up to 3 are acceptable but over 3 indicates that you are losing radiated power and antenna adjustment 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 mic
29. the microphone is readily accessible Section Ill Insalla on ee lf e 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 tumed off The unit requires very little current and therefore will not significantly discharge the vehicle battery Even though the COBRA 148GTL has ANL and NB controls in some installations ignition interference may be high enough to make good communications impossi ble 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 locating 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 antenn
30. ting Temperature Range Microphone Input Voltage Current Drain Size Weight Antenna Conductor Semiconductors Meter 3 in 1 TRANSMITTER Power Output Modulation Intermodulation Distortion SSB Carrier Suppression Unwanted Sideband Frequency Response Output Impedance Output Indicators 40 AM 4OLSB 40 USB 26 965 to 27 405 MHz Phase Lock Loop PLL synthesizer 0 005 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 Maximum audio output 0 6A 2 3 g H x 7 7 g W x 9 Lamy 5 Ibs UHF S0239 3 field effect transistors 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 qB 55 GB 50 cB AM and SSB 300 to 2500 Hz 50 ohms unbalanced Meter shows relative RF output power and SWR Transmit LED glows red when transmitter is in operation 3 RECHVER Sensitivity Selectivity Image Rejection IF Frequency Adjacent Channel Rejection AM and SSB RF Gain Control Automatic Gain Control AGC Squelch ANL Noise Blanker Voice
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