Cobra 25 LTD ST User Guide

OPERATING INSTRUCTIONS FOR YOUR
40 CHANNEL
CITIZENS BAND
2-WAY MOBILE RADIO
Model
25 LTD ST
Cobra Electronics Corporation
Chicago, IL 60707
PRINTED IN HONG KONG ©COBRA ELECTRONICS CORP. 1997 480-205-P-001
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, SoundT racker 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.
The CB Story
1
How To Use Your
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
Specifications (cont.)
GENERAL
Channels 40 Frequency Range 26.965 to 27.405 MHz. Frequency Control Phase Lock Loop (PLL) synthesizer. Frequency Tolerance 0.005%. Operating Temperature Range -30¡ C to + 50¡ C. Microphone Plug-in dynamic. Input Voltage 13.8VDC nom.(positive or negative ground). Current Drain Transmit: AM full mod., 1.5A (maximum)
Receive: Squelched, 0.3A; full audio output, 1.2A
(nominal). Size 8 5/8Ó D x 7 9/32Ó W x 2 13/64Ó H . Weight 4 lbs. Antenna Connector UHF, SO-239. Semiconductors 26 transistors, 26 diodes, 4 integrated circuits. Meter Illuminated; indicates relative power output and
received signal strength.
TRANSMITTER
Power Output 4 watts. Modulation AM (Amplitude Modulation). Frequency Response 300 to 3000 Hz. Output Impedance 50 ohms, unbalanced.
RECEIVER
Sensitivity Less than 1 µV for 10dB (S+N)/N. Selectivity 6dB @ 7 KHz, 60 dB @ 10 KHz. Image Rejection 80 dB, typical. Adjacent-Channel Rejection 60 dB, typical. IF Frequencies Double Conversion: 1st: 10.695 MHz.
2nd: 455 KHz.
Automatic Gain Control (AGC) Less than 10 dB change in audio output for inputs
from 10 to 50,000 microvolts. RF Gain Control Adjustable for optimum signal reception. Noise Blanker RF type. Squelch Adjustable; threshold less than 1µV. Audio Output Power 4 watts. Frequency Response 300 to 3000 Hz. Distortion Less than 7% @ 3 watts @ 1000 Hz. Built-in Speaker 16 ohms, round. External Speaker (Not Supplied) 8 ohms; disables internal speaker when connected.
PA SYSTEM
Power Output 4 watts into external speaker. External Speaker for PA 8 ohms, when PA-CB switch is in PA, the PA speaker (Not Supplied) also monitors the receiver; separate jack provided.
(SPECIFICATIONS SUBJECT TO CHANGE WITHOUT NOTICE)
3
FREQUENCY RANGE The COBRA 25 LTD ST transceiver represents one of the most advanced 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 providing complete coverage of all 40 channels as shown below.
Channel Channel Frequency Channel Channel Frequency
in MHz in MHz
1 26.965 21 27.215 2 26.975 22 27.225 3 26.985 23 27.255 4 27.005 24 27.235 5 27.015 25 27.245
6 27.025 26 27.265 7 27.035 27 27.275 8 27.055 28 27.285 9 27.065 29 27.295 10 27.075 30 27.305
11 27.085 31 27.315 12 27.105 32 27.325 13 27.115 33 27.335 14 27.125 34 27.345 15 27.135 35 27.355
16 27.155 36 27.365 17 27.165 37 27.375 18 27.175 38 27.385 19 27.185 39 27.395 20 27.205 40 27.405
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.
2
Specifications
5
Installation (Cont.)
3. 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."
4. Connect the red lead of DC power cord to +13.8 VDC. In automobile instal-
lations, +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).
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.
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.
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.
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:
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.
2. Drill necessary holes and secure mounting bracket in location.
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