Cobra 148gtle Cb Tranciever Manual

OPERATING INSTRUCTIONS FOR YOUR
40 CHANNEL
CITIZENS BAND
SSB/AM 2-WAY 
MOBILE RADIO
Model 148 GTL
PRINTED IN CHINA ©2002 COBRA ELECTRONICS CORPORATION 480-046-P
6500 WEST CORTLAND STREET
CHICAGO, IL 60707 USA
Nothing
comes close to a Cobra™ 

Serial No.Date of PurchaseDealer Name
Keep this manual for detailed information 
about your Cobra CB Radio System.
SAVE YOUR SALES RECEIPT, THE 
CARTON AND “PACKING” FOR 
POSSIBLE FUTURE USE.If You Think You Need Service, 
please contact your local dealer.The Cobra
®line of quality products includes:
CB radios
microTALK
®radios
Radar/Laser Detectors
GPS
Safety Alert®
Traffic Warning Systems
Accessories
HighGear
™ Accessories
How To  Use Your40-CHANNEL, 
CITIZENS BAND 
SSB/AM 2-WAY MOBILE RADIOModel 148...

Section I Introduction
FREQUENCY RANGE
The COBRA 148GTL transceiver represents one of the most advanced SSB/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, which is used 
in the AM mode and in the upper and lower single sideband modes, providing
complete coverage of all 40 channels shown below.
Channel Channel Frequency 
in MHz
126.965
226.975
326.985
427.005
527.015
627.025
727.035
827.055
927.065...

RECEIVER
Sensitivity SSB: 0.25 µV for 10dB (S+N)/N at greater than
1/2-watt of audio output. 
AM: 0.5 µV 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.
IF Frequency AM: 7.8 MHz 1st IF, 455 KHz 2nd IF. 
SSB: 7.8 MHz.
Adjacent-Channel Rejection 60 dB AM & 70 dB SSB.
AM and SSB RF Gain Control 40 dB adjustable for optimum signal reception.
Automatic Gain Control (AGC) Less than 10...

Section III Installation  (Continued)
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 generator 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...

Section III Installation (Continued)
D.Try a different location on your car (keeping in mind the radiation pattern 
you wish).
E.Is the antenna perfectly vertical?
F.Try a different location in your neighborhood. Stay away from large metal
objects when adjusting (metal telephone or light posts, fences, etc.).
NOTE
The COBRA 148GTL will operate into an SWR of 2 to 1 indefinitely
and sustain an SWR of 20:1 for a maximum of 5 minutes at rated 
operating conditions.
EXTERNAL SPEAKER
The external speaker jack...

10
Section IV Operation (Continued)
4. SWR CAL CONTROL (outer dual concentric). In order for you to achieve
maximum radiated power and the longest range, it is important that your
antenna be in good condition, properly adjusted and matched to your
transceiver.  The Built-in SWR (standing wave ratio) meter lets you easily
measure your antenna condition. To operate this function, connect your
antenna to the transceiver antenna output connector. Select a channel near
the middle of the band such as 21 or the...

Section IV Operation (Continued)
B. INDICATOR 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 ratio of standing wave voltage and RF
output. Used to properly adjusts the length of the antenna, and to monitor the
quality of the coaxial cable and all RF electrical connections. If there is any
degradation whatsoever in any of the above, due to humidity, salt, spray,...

Section IV Operation (Continued)
pitched whistle or a high-pitched whistle) you will hear the increase in the output
tone of the receiver. If the incorrect mode is selected, an increase in tone of a
whistle applied to the transmitter will cause a decrease in the resultant tone from
the receiver.
Thus when a voice is used in place of a whistle or tone, in the proper listening
mode the voice will be received correctly whereas in the incorrect mode, the
voice will be translated backwards and cannot be made...

Section IV Operation (Continued)
Fig. 2.Microphone Cable Preparation.
To wire the microphone cable to the plug provided, proceed as follows:
Fig. 3. Microphone plug wiring.
1.Remove the retaining screw.
2.Unscrew the housing from the pin receptacle body.
3.Loosen the two cable clamp retainer screws.
4.Feed the microphone cable through the housing, knurled ring and washer as
shown Fig. 3B.
5.The wires must now be soldered to the pins as indicated in the above wiring
tables. If a vise or clamping tool is...