Cobra 25WX-ST User Guide

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TX PWR

OPERATING INSTRUCTIONS FOR YOUR

40 CHANNEL

CITIZENS BAND

2-WAY MOBILE RADIO

Model

25 WX ST

Cobra Electronics Corporation

6500 W. Cortland Street

Chicago, IL 60707

PRINTED IN HONG KONG ©COBRA ELECTRONICS CORP. 1997 480-210-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 Acitizens 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

What Is Weather Radio?

NOAA WEATHER RADIO (NWR) is a service of the National Oceanic and
Atmospheric Administration (NOAA), of the U.S. Department of Commerce. It pro­vides continuous, around-the-clock broadcasts of the latest weather information
directly from National Weather Service Offices. The broadcasts are tailored to the
weather-information needs of people within the receiving area. For example, coastal
and Great LakesÕ stations provide specialized weather information for area boaters,
fishermen and others engaged in marine activities, as well as general weather infor­mation for the public-at-large. Three hundred eighty (380) NWR stations are in oper­ation by the U.S. Government in addition to several NWR stations that are main­tained by private interest groups.

Under the January 1975 White House policy statement, NOAA Weather Radio was des­ignated as the sole Government operated radio system to provide direct warnings into
private homes for both natural disasters and nuclear attack. The capability is to sup­plement warnings by sirens and by commercial radio and television.

NWR Frequencies and Transmission Characters

NWR broadcasts have been allocated seven frequencies within the VHF radio spec­trum reserved for Government use. Assigned frequencies are:

162.400 MHz 162.475 MHz 162.525 MHz

162.425 MHz 162.500 MHz 162.550 MHz

162.450 MHz

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.

The CB Story

1

How To Use Your

Citizens Band

2-Way Mobile Radio

Model 25 WX ST

Contents Page

The CB Story ............................................................................................1

SoundTracker System ............................................................................1

What is Weather Radio? ........................................................................1

Specifications........................................................................................2,3

Installation

Location..................................................................................................4

Mounting Connections ....................................................................4, 5

CB Antenna ..........................................................................................6

Ignition Noise Interference ................................................................7

Operation

Controls and Indicators ............................................................8, 9, 10

Operating Procedure to Receive ......................................................11

Operating Procedure to Transmit ....................................................11

Operating Procedure to Receive Weatherband..............................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

“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

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)

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Specifications (cont.)

Specifications

FREQUENCY RANGE
The COBRA 25 WX 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 WX 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.

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Installation (Cont.)Installation

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. When 13.8 volts DC is initially applied to radio, the radio will turn on

(when power switch is in OFF position) for 1 second. This is the emergency
weather alert normal initialization procedure.

7. 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.

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.