Cobra_21ltd St Cb Tranciever_manual

OPERATING INSTRUCTIONS FOR YOUR
40 CHANNEL
CITIZENS BAND 
2-WAYMOBILE RADIO
Model21 LTD STCobra Electronics Corporation
6500 W. Cortland Street
Chicago, IL 60707
PRINTED IN HONG KONG©COBRAELECTRONICS CORP. 1997480-221-P-00121LTDST.MANUAL.REV.QX  9/25/98 10:59 AM  Page 1 

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 commu-
nications service was opened in 1959. (CB also includes a Class Acitizens band
and Class C remote control frequencies.)
FCC regulations permit only “transmissions” (one party to another) rather than
“broadcasts” (to a wide audience). Thus, advertising is not allowed on CB
Channels because that is “broadcasting.”
“Cuts Static coming in, adds Punch going...

Specifications (cont.)
GENERAL
Channels40 
Frequency Range26.965 to 27.405 MHz.
Frequency ControlPhase Lock Loop (PLL) synthesizer.
Frequency Tolerance0.005%.
Operating Temperature Range-30° C to + 50° C.
MicrophonePlug-in dynamic.
Input Voltage13.8VDC nom.(positive or negative ground).
Current DrainTransmit:AM full mod., 1.5A(maximum)
Receive: Squelched, 0.3A; full audio output, 1.2A
(nominal).
Size53
/
4” W  x 1 3
/
4” H  x 7 1
/
2” D .
Weight1.2 lbs.
Antenna ConnectorUHF, SO-239.
Semiconductors26...

5Installation (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 oper-
ating the unit without the vehicles engine running.
Before installing the CB radio,...

7 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 fromthe 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 transceivermay be operated with vehicle engine turned off....

Operation (Cont.)
9 6.RX/TX LEDINDICATOR.When your radio is in the CB receive mode,
the LED will be green. When in transmit mode, the LED will be red.
7.LED CHANNELDISPLAY.The selected channel will be displayed. 
8.CB-PASWITCH:Selects the mode of operation. In the CB position, the
PAfunction is disabled and the unit will transmit and receive on the
selected frequency.The PAfunction should not be used unless a PAspeaker is
connected. NOTE: ANL(Automatic Noise Limiter) is a non-switchable
feature that is...

11 Operating Procedure to Receive
1.Be sure that the power cord, antenna and microphone  are connected to the
proper connectors before proceeding further. The PA/CB  should be in the
CB position.
2.Turn the radio ON by rotating the VOLUME CONTROLclockwise.
3.Set the RF GAIN CONTROLfully clockwise.
4.Set DELTA-TUNE CONTROLto center(click-stop) position.
5.Rotate SQUELCH CONTROLc o u n t e rclockwise until incoming signal is heard .6.Set the CHANNELSELECTORSwitch to the desired channel.
7.Set VOLUME...

13 12 Operation (Cont.)
Operating Procedure to Transmit
1.Be sure the operator has read and understands part 95, F.C.C. Rules and
Regulations prior to operating the transmitter.
2.Select the desired channel.
3.Set the DYNAMIKE control fully clockwise.
4.The receiver and transmitter are controlled by the press-to-talk switchon the
microphone. Press the switch and the transmitter is activated; release switch
to receive. When transmitting (on a clear channel), hold the microphone two
inches from the mouth...

1415The COBRACB transceiver is specifically designed for the environment encoun-
tered in mobile installations. The use of all solid state circuitry and its light weight
result in high reliability. Should a failure occur, however, review the following,
then if necessary, replace parts only with identical parts. Do not substitute. Refer
to the schematic diagram and parts. 
1.Check connections to the source of power and make sure it is the 13.8 VDC
required to operate your radio.
2.Check the fuse in the DC...

Appendix (Cont.)
AFew Rules That Should Be Obeyed
1.You are not allowed to carry on a conversation with another station for more
than five minutes at a time without taking a one-minute break to give others
a chance to use the channel.
2.You are not allowed to blast others off the air by overpowering them with
illegally amplified transmitter power or illegally high antennas.
3.You can’t use the CB to promote illegal activities.
4.You are not allowed to use profanity.
5.You may not play music in your CB....