OPERATING INSTRUCTIONS FOR YOUR 40 CHANNEL CITIZENS BAND 2-WAY MOBILE RADIO Model 25 LTD ST Cobra Electronics Corporation 6500 W. Cortland Street Chicago, IL 60707 PRINTED IN HONG KONG ©COBRA ELECTRONICS CORP. 1997 480-205-P-001 How To Use Your 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 communications service was opened in 1959. (CB also includes a Class A citizens band and Class C remote control frequencies.) FCC regulations permit only ÒtransmissionsÓ (one party to another) rather than ÒbroadcastsÓ (to a wide audience). Thus, advertising is not allowed on CB Channels because that is Òbroadcasting.Ó "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 transferred more effectively through cluttered airwaves. It literally ÒpunchesÓ 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 CobraÕs SoundTracker system to significantly reduce the amount of static on all incoming CB signals. The system can be further optimized when two SoundTracker CBÕs 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 OperatorÕs 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. Citizens Band 2-Way Mobile Radio Model 25 LTD ST Contents Page The CB Story ............................................................................................1 SoundTracker System ............................................................................1 Specifications ........................................................................................2,3 Installation Location..................................................................................................4 Mounting Connections ....................................................................4, 5 CB Antenna ..........................................................................................6 Ignition Noise Interference ................................................................7 In House Operation..............................................................................7 Operation Controls and Indicators ............................................................8, 9, 10 Operating Procedure to Receive ......................................................11 Operating Procedure to Transmit ....................................................12 How SoundTracker Works................................................................13 Maintenance and Adjustment ............................................................14 Appendix Ten Code ..............................................................................................15 A Few Rules That Should Be Obeyed ............................................16 How Your CB Can Serve You ..........................................................16 Warranty Service Instructions ............................................................17 Limited Two Year Warranty ................................................................18 Accessories..................................................................Inside Back Cover 1 Specifications FREQUENCY RANGE The COBRA 25 LTD ST transceiver represents one of the most advanced AM twoway radios ever designed for use as a Class D station in the Citizens Radio Service. This unit features advanced Phase Lock Loop (PLL) circuitry providing complete coverage of all 40 channels as 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 Specifications (cont.) Channels Frequency Range Frequency Control Frequency Tolerance Operating Temperature Range Microphone Input Voltage Current Drain 40 26.965 to 27.405 MHz. Phase Lock Loop (PLL) synthesizer. 0.005%. -30¡ C to + 50¡ C. Plug-in dynamic. 13.8VDC nom.(positive or negative ground). Transmit: AM full mod., 1.5A (maximum) Receive: Squelched, 0.3A; full audio output, 1.2A (nominal). 8 5/8Ó D x 7 9/32Ó W x 2 13/64Ó H . 4 lbs. UHF, SO-239. 26 transistors, 26 diodes, 4 integrated circuits. Illuminated; indicates relative power output and received signal strength. 4 watts. AM (Amplitude Modulation). 300 to 3000 Hz. 50 ohms, unbalanced. Less than 1 µV for 10dB (S+N)/N. 6dB @ 7 KHz, 60 dB @ 10 KHz. 80 dB, typical. 60 dB, typical. Double Conversion: 1st: 10.695 MHz. 2nd: 455 KHz. Less than 10 dB change in audio output for inputs from 10 to 50,000 microvolts. Adjustable for optimum signal reception. RF type. Adjustable; threshold less than 1µV. 4 watts. 300 to 3000 Hz. Less than 7% @ 3 watts @ 1000 Hz. 16 ohms, round. 8 ohms; disables internal speaker when connected. 4 watts into external speaker. 8 ohms, when PA-CB switch is in PA, the PA speaker also monitors the receiver; separate jack provided. Size Weight Antenna Connector Semiconductors Meter TRANSMITTER Power Output Modulation Frequency Response Output Impedance RECEIVER Sensitivity Selectivity Image Rejection Adjacent-Channel Rejection IF Frequencies Automatic Gain Control (AGC) RF Gain Control Noise Blanker Squelch Audio Output Power Frequency Response Distortion Built-in Speaker External Speaker (Not Supplied) The COBRA 25 LTD ST has a vastly superior receiver which includes noise blanker circuitry and an automatic noise limiter. 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. Fill out below; keep for your records. Serial No. Date of Purchase Dealer Name Keep this manual for detailed information about your Cobra CB radio. SAVE YOUR SALES RECEIPT, CARTON AND PACKING FOR POSSIBLE FUTURE USE. PA SYSTEM Power Output External Speaker for PA (Not Supplied) (SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE) 2 3 Installation Location 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 to the underneath of the dash panel, with the microphone bracket beside it. Installation (Cont.) 3. 4. Connect the antenna cable plug to the standard receptacle on the unit. Most CB antennas are terminated with a type PL-259 plug which mates with the receptacle marked "ANT." Connect the red lead of DC power cord to +13.8 VDC. In automobile installations, +13.8 VDC is usually obtained from the accessory contact in the fuse box. This prevents the set being left on accidentally and also permits operating the unit without the vehicle's engine running. Before installing the CB radio, visually check the vehicle battery connections to determine which battery terminal, positive or negative (positive is the larger of the two) is grounded to the engine block (or chassis). Mounting and Connection The transceiver is held in the universal mounting bracket by two thumbscrews, permitting adjustment at the most convenient angle. A universal mounting bracket is supplied along with self tapping screws and star washers. The mounting must be mechanically strong and also provide a good electrical connection to the chassis of the vehicle. To mount the transceiver: 5. Connect the black lead to the negative side of the automobile. This is usually the chassis of the car. Any convenient location with good electrical contact (remove paint) may be used. Plug power cable into jack on back of transceiver. In positive ground automobiles the red wire goes to the chassis and the black wire is connected to the ignition switch. 1. Determine the most convenient location in your vehicle, hold the COBRA radio with mounting bracket in the exact location desired. If nothing will interfere with mounting it in the desired position, remove the mounting bracket and use it as a template to mark the location for the mounting screws. Drill necessary holes and secure mounting bracket in location. 6. Mount microphone bracket on right side of the transceiver, or near it using two screws supplied. When mounting in an automobile, place the bracket under the dash so the microphone is readily accessible. 2. 4 5 Installation (Cont.) CB 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 SO-239) is provided on the transceiver for easy connection to a standard PL 259 cable termination. Cobra loaded type antenna models are highly recommended for most installations. Consult your Cobra dealer for further details, or call 773-889-3087 and speak to a Cobra customer representative. 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. 3-Way Combination Antennas are available which allow operation of all three bands (AM-FM & CB), using a single antenna. However, use of this type of antenna usually results in less than normal transmit and receive range when compared to a standard-type "Single Band" antenna designed for CB only. The quality of reception of radio signals is highly dependent on the antenna system. Call 773-889-3087 for further information. Installation (Cont.) 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 alternator 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 25 LTD ST has an automatic noise limiter, 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 fo ...