Instruction/ maintenance manual of the product 148 GTL Cobra Electronics
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Ho w T o Use Y our 40-CHANNEL, CITIZENS B AND SSB/AM 2-W A Y MOBILE RADIO Model 148 GTL Contents P age T he CB Story .................................................................................... 1 Section I: Introduction .......................
Section I Intr oduction FREQUENCY RANGE T he COBRA 148GTL transceiv er represents one of the most adv anced SSB/AM two- wa y radios ever designed for use as a Class D station in the Citizens Radio Service.
RECEIVER Sensitivity SSB: 0.25 µ V for 10dB (S+N)/N at greater than 1/2-watt of audio output. AM: 0.5 µ V for 10 dB (S+N)/ at greater than 1/2-watt of audio output. Selectivity AM: 6dB @ 3 KHz, 50 dB @ 9 KHz. SSB: 6 dB @ 1.1 KHz, 60 dB @ 2.3 KHz. Image Rejection More than 65 dB .
Section III Installation (Continued) IGNITION NOISE INTERFERENCE Use of a mobile receiv er at low signal levels is normally limited b y the presence of electrical noise. The primary sour ce of noise in automobile installations is from the generator and ignition system in the v ehicle.
Section III Installation (Continued) D . T ry a different location on y our car (keeping in mind the radiation pattern you wish). E. Is the antenna perfectly vertical? F . T ry a different location in y our neighborhood. Stay a wa y from large metal objects when adjusting (metal telephone or light posts, fences, etc.
10 Section IV Oper ation (Continued) 4. SWR CAL CONTROL (outer dual concentric) . In order for you to ac hieve maximum radiated po wer and the longest range, it is important that y our antenna be in good condition, properly adjusted and matched to y our trans- ceiv er .
Section IV Oper ation (Continued) B. INDICA TOR FUNCTIONS 1. S-METER. Swings proportionally to the strength of the incoming signal. 2. RF METER . Swings proportionally to the RF output power . 3. SWR METER . Swings proportionally to the r atio of standing w a v e voltage and RF output.
Section IV Oper ation (Continued) T hus when a v oice 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 tr anslated backwards and cannot be made intelligible b y the voice lock control.
Section IV Oper ation (Continued) Fig. 2. Microphone Cable Preparation T o wire the microphone cable to the plug provided, proceed as follo ws. Fig. 3 . Microphone plug wiring. 1. Remove the retaining screw . 2. Unscrew the housing from the pin receptacle bod y .
18 Section V Maintenance and Adjustment T he COBRA 148GTL transceiv er is specifically designed for the environment en- countered in mobile installations. T he 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.
Section VI Appendix (Continued) A FEW RULES THA T SHOULD BE OBEYED 1. Y ou are not allowed to carry on a con versation with another station for more than fiv e minutes at a time without taking a one-minute break, to give others a chance to use the c hannel.
If Y ou Need Ser vice If Y ou T hink Y ou Need Service, Call 773-889-3087 Y ou ma y be asked to send your unit to the Cobr a factory . It will be necessar y to furnish the following, in or der to hav e the product serviced and r eturned.
Description Part No. Cost Ea. X Qty . = Amount Replacement microphone with 4-pin connector for 148 GTL CA-73 $19.95 MOBILE POWER MICROPHONE Amplified Power Microphone with 4-pin connector for 148 GTL CA-75 $19.95 NOISE CANCEL MICROPHONE for 148 GTL CA-77 $39.
2 PRINTED IN THAILAND ©COBRA ELECTRONICS CORPORA TION 1996 480-163-P- 001 Cobr a Electronics Corpor ation 6500 W . Cortland Street Chicago, IL 60707.
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