OPERATING INSTRUCTIONS FOR YOUR 40 CHANNEL CITIZENS BAND SSB/AM 2-WAY MOBILE RADIO Model 148 GTL Nothing comes close to a CobraTM PRINTED IN CHINA ©2002 COBRA ELECTRONICS CORPORATION 6500 WEST CORTLAND STREET CHICAGO, IL 60707 USA 480-046-P How To Use Your Serial No. Date of Purchase Dealer Name Keep this manual for detailed information about your Cobra CB Radio System. SAVE YOUR SALES RECEIPT, THE CARTON AND "PACKING" FOR POSSIBLE FUTURE USE. 40-CHANNEL, CITIZENS BAND SSB/AM 2-WAY MOBILE RADIO Model 148 GTL Contents Page Section I: Introduction ..........................................................................................2 Section II: Specifications ....................................................................................3, 4 Section III: Installation ..............................................................................5, 6, 7, 8 Section IV: Operation........................................................................................9-17 Controls and Indicators ..........................................................................................9 A.Control Functions....................................................................................9, 10, 11 The Cobra® line of quality products includes: CB radios microTALK radios Radar/Laser Detectors GPS Safety Alert Traffic Warning Systems Accessories HighGearTM Accessories ® ® B.Indicator Functions ............................................................................................12 Operating Procedure to Receive ..........................................................................12 Operating Procedure to Transmit ..........................................................................13 Receiving SSB Signals ....................................................................................13, 14 Alternate Microphones and Installation ....................................................15, 16, 17 Section V: Maintenance and Adjustment ........................................................18-21 Section VI: Appendix ................................................................................19, 20, 21 Ten Code ..............................................................................................................19 A few Rules That Should Be Obeyed ....................................................................20 How Your CB Can Serve You ................................................................................20 Use Channel 9 for Emergency Messages Only ......................................................21 If You Think You Need Service, please contact your local dealer. Section I Introduction FREQUENCY RANGE The COBRA 148GTL transceiver represents one of the most advanced SSB/AM two-way radios ever designed for use as a Class D station in the Citizens Radio 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 complete coverage of all 40 channels shown below. Channel 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Channel Frequency in MHz 26.965 26.975 26.985 27.005 27.015 27.025 27.035 27.055 27.065 27.075 27.085 27.105 27.115 27.125 27.135 27.155 27.165 27.175 27.185 27.205 Channel 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 Channel Frequency in MHz 27.215 27.225 27.255 27.235 27.245 27.265 27.275 27.285 27.295 27.305 27.315 27.325 27.335 27.345 27.355 27.365 27.375 27.385 27.395 27.405 GENERAL Section II Specifications Channels Frequency Range Frequency Control Frequency Tolerance Frequency Stability Operating Temperature Range Microphone Input Voltage Current Drain 40 AM, 40 LSB, 40 USB. 26.965 to 27.405 MHz. Phase Lock Loop (PLL) synthesizer. 0.005%. 0.001%. -22° F to +122° F (-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 3/8"(H) x 7 7/8"(W) x 9 1/4"(D). (6 cm (H) x 20 cm (W) x 23.5 cm (D)). 5 lbs. (2.27 kg). 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. 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 The COBRA 148GTL 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 operating instructions in this manual. 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. Meter shows relative RF output power and SWR. Transmit LED glows red when transmitter is in operation. 2 3 Section II Specifications (Cont.) RECEIVER Sensitivity SSB: 0.25 µV for 10dB (S+N)/N at greater than 1/2-watt of audio output. AM: 0.5 µV for 10 dB (S+N)/ at greater than 1/2watt 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 dB. AM: 7.8 MHz 1st IF, 455 KHz 2nd IF. SSB: 7.8 MHz. 60 dB AM & 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 µV. 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. LOCATION Section III Installation Plan the location of the transceiver and microphone bracket before starting the installation. 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 usually mounted below the dash panel, with the microphone bracket beside it. 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 (Not Supplied) MOUNTING THE CONNECTION The COBRA 148GTL 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 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 receiver in the car. 4. Connect the black lead to -13.8V DC. This is usually the chassis of the car. Any convenient location with good electrical contact (remove paint) may be used. PA SYSTEM Power Output External Speaker for PA (Not Supplied) 4 watts into external speaker. 8 ohms. 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 the microphone is readily accessible. (SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE) 4 5 Section III Installation (Continued) 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 COBRA 148GTL has ANL and NB controls, in some installations ignition interference may be high enough to make good communications impossible. The electrical noise may come from several sources. Many possibilities exist 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 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 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 purposes, however, the radiation pattern is nondirectional. The slight directional characteristic will be observed only at extreme distances. 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. 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 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 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 ...