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Cobra Communications Product Group
DYNASCAN CORPORATION
6500 W. Cortland Street
Chicago, Illinois 60635
480-236-9001A O DYNASCAN CORP,, 1983 Printed in: the Philippines
UTDS0151328
obra
Cobra 2000GTL
40-Channel
Solid State Citizens Band
SSB/AM Two-Way Radio
Base Station
With Separate Speaker Cabinet
Cobra Communications Product Group
DYNASCAN CORPORATION
6500 We. Cortland Street
Chicago, lilinois 60635
INSTRUCTION MANUAL
for
Cobra 2000GTL
40-Channel
Citizens Band Solid State
SSB/AM Two-Way Radio
Base Station With
Separate Speaker Cabinet
4
Sê.
Cobra Communications Product Group
DYNASCAN CORPORATION
6500 W. Cortland Street
Chicago, Illinois 60635
WARNING — TO PREVENT FIRE OR SHOCK HAZARD,
DO NOT EXPOSE THIS APPLIANCE TO RAIN OR MOISTURE.
Section 1
Specifications
GENERAL
Channels
Frequency Range
Frequency Control
Frequency Tolerance
Operating Temperature Range
Microphone
Power Source
Power Consumption
(120 AC)
Current Drain (13.8V DC)
Size
Weight
Antenna Connector
Semiconductors
Meter 1
Meter 2
40.
26.965 to 27.405 MHz.
Phase Locked Loop (PLI) synthesizer.
*+130 Hz Typical
-30C to +50,
Plug-in type; 60092 dynamic.
120V AC nominal.
13.8V DC nominal.
(Positive or negative ground).
Transmit: AM full mod., 65 watts.
SSB 70 watts.
Receive: Squelched, 30 watts.
Full audio, 40 watts.
Transmit: AM and SSB, 2.24 DC (nominal).
Receive: — Full audio output, 1.14 DC
(nominal).
No signal, (0.654 DC (nominal)
SH) x 15º(W) x 4-7/16"(D)
19% pounds. (including speaker)
UF, S0239.
18 integrated circuíts, 6 FETs, 76 transistors,
93 diodes, 12 LEDs and 1 SCR.
Hluminated; indicates relative power output
and received signal strength.
Iluminated, indicates standing wave ratio
and level of modulation.
TRANSMITTER
Power Output
Modulation
Intermedualtion Distortion
SSB Carrier Suppression
Unwanted Sidehand
Frequency Response
Output Impedance
SSB Tilter
Output Indicators
RECEIVER
Sensitivity
Selectivity
Image Rejection
IF Frequeney
Adjacent-Channel Rejection
AM and SSB RF Gain Control
Automatic Gain Control
(AGO)
Squelch
ANI
AM. 4 watts.
SSB, 12 watts, PEP.
AM, high-and low-level Class B.
SSB: 3rd and Sth order, more than -25dB.
7th and 9th order, more than -35dB.
-5S dB Nominal
-SO dB Nominal.
AM and SSB: 300 to 2500 Hz.
50 ohms, unbalanced.
7.8 MHz, crystal lattice type:
Meters show relative RF output power, per-
centage of modulalion and SWR.
“ON THE AIR” Transmit Indicator.
SSB: 0.25 uV for 10 dB (S+NY/N at greater
than lé-walt of audio output
AM: 0.5 uV for 10dB (S+N)/ at greater than
att of audio output.
AM: 6 dB 63 KHz, 50 dB 29 KHz.
SSB: 6 dB 7.1 KHz, 60 dB €2,3 KHz.
More than 65 dB.
AM: 7.8 MHz Ist IF, 455 KHz 2nd IF
SSB: 7.8 MHz
60 dR AM & 70 dB SSB.
40 dB adjustable for optimum signal reception
Less than 10 dB change in audio output for
inputs from 10 to 100,000 microvolts.
Adjustable; Lhreshold less than 0.5 uV.
Switchable.
Noise Blanker RE type, effective on AM and SSB.
Voice Lock Range 41.5 KHz. coarse 500 Hz fine
RE Gain Control Adjustable for optimum signal reception
Audio Output Power 4 watis into 8 ohm.
Frequency Response 300 to 2500 Hz.
Distortion Less lhan 10% at 3 watts output.
Separate Speaker 8 ohms.
External Speaker (not supplied) 4 — 8 ohms.
Indicators “Receive” indicator. Meter shows receive
signal strength.
Headphone Output 8 ohm impedance, 10 mW output.
AUX Output 100K ohm impedance, approx. 300 mW
output.
PA SYSTEM
Power output 4 watts into extemal speaker
External speaker for PA 4 & ohms. (not supplied)
CLOCK/COUNTER
Clock Uses 60 Hz power line reference. May be
used to sound alamm or tum on radiv.
Counter Displays transmit and receive frequency.
Section Ill
Installation
LOCATION
Prior to beginning operation of the transceiver, a basic installation must be
prepared. Installation of the transceiver itself is a rather simple procedure.
In selecting the location for the unit, three basic factors must be considered.
1. Access to a 120V, 60 Hz power source.
2. The location must be convenient for running the antenna leadiin cable
if an outside antenna installation is proposed.
3. ACDC switch on rear paneluse “AC” for 120 volt operation and
“DC” for battery operation.
BASE STATION ANTENNA
Since the maximum allowable power output of the transmitter is limited by
the FCC, the antenna is the most important factor aflecting transmission
distance. Only a properly matched antenna system will allow maximum power
transfer from the 50-ohm transmission line to the radiating element.
The recommended method of antenna tuning is to use the built in SWR
meter to adjust the antenna tuning for minimum reflected power on channel
21.
The radio may be used with any type of 50-ohm base station antenna. A
ground plane vertical antenna will provide the most uniform horizontal coverage.
This type of antenna is best suited for communication with a mobile unit. For
point-to-point operation where both stations are fixed, a directional beam will
usually increase communicating range since this type of antenna concentrates
transmitted energy in one direction. The beam antenna also aliows the receiver
to “listen" in only one direction thus reducing interfering signals.
Antenna height is an important factor when maximum range is desired.
Keep the antenna clear of surrounding structures or foliage. FCC regulations for
base station antenna height are:
1. Omni-directional antennas may not be higher than 60 feet above the
ground when using a tower, mast or pole, and no higher than 20 feet
above an existing structure.
2. Beam antennas may not be higher than 20 feet above the ground when
using a tower, mast, pole, or an existing structure.
These are only general regulations applicable to most but not all parts of the
nation. Locations near airports and sume military installations are subject to
different rules; therefore, it is best to contact your nearest Federal Communica-
tions Commission office for information regarding your specific area.
MOBILE OPERATION/EMERGENCY POWER OPERATION
Ir is possible to operate the COBRA 2000GTL from an external 13.8V DC
power supply for emergency power conditions or from an automobile battery
for mobile operation. The COBRA 2000GTL is supplied with a polarized plug
for operation on an external DC supply.
The negative lead is black.
The positive lead is red and has an inline fuse holder as an integral part of
the positive lead.
AC-DC switch on rear panel-use “AC” for 120 volt operation and “DC” for
battery operation.
PUBLIC ADDRESS
An external 8-ohm, 4-watt speaker may be connected to the PA speaker
jack located on the rear panel when the transceiver is used as a public address
system. The speaker should be directed away from the microphone to prevent
acoustic fecd-back. Physical separation or isolation of the microphone and
speaker must be used when operating the PA at high-output levels.
REMOTE SPEAKER
The external speaker jack (SPI and SP2) are located on the rear panel.
An external speaker should have 8 ohms impedance and be able to handle at
least 4 watts. Use one jack for speaker supplied with 2000GTL. The other
speaker is available for use of optional speaker CA-2000 (available through your
authorized COBRA DEALER.)
Section IV
Operation
CONTROLS AND INDICATORS
There are 25 controls, 2 meters, £ indicators and 3 jacks on the front panel
of your COBRA 2000GTL.
A. CONTROL FUNCTIONS
1. POWER SWITCH. Press in to tum on radio. Press in knob all the way
and release to tum off radio.
2. DYNAMIKE PLUS. Adjusts the microphone gain in the transmit and
PA modes. This controls the gain to the extent that full talk power is
available several inches away from the microphone. In the public
address (PA) mode the control functions as the volume control.
3. VOLUME. Turn clockwise ta set the desired listening level.
4, SQUELCH. This control is used to cut off or eliminate receiver
background noise in the absence of an incoming signal. For maximum
receiver sensitivity the control should be adjusted only to the point
where the receiver background noise or ambient background noise is
eliminated. Tum fully counterclockwise then slowly clockwise until
receiver noise disappears. Any signal to be received must now be
slightly stronger than the average received noise. Further clockwise
rotation will increase the threshold level which a signal must overcome
in order to be heard. Only strong signals will be heard at a maximum
clockwise setting.
O!
E. FREQUENCY COUNTER/LED DIGITAL CLOCK
1. Located on right hand side of the counter/clock is the time and MHz
indicator. This indicator identified the mode display.
to
Located on the left hand side of the counter/clock is the AM and PM
indicators.
3. The flashing colon indicates seconds.
For the proper procedure to set your LED clock, there are the
following features:
TIME SET - 3 switches (used to set time)
DYNALERT - 3 switches (used to set alarm and radio)
COUNTER/CLOCK - 3 switches (used to select display)
Follow the instructions as listed below:
TIME SET
TIME SET SWITCH - Depress this switch with hour switch or minute
switch for setting correct time.
HOUR SWITCH - Depress this switch at the same time with time set
switch to get correct hour setting.
MINUTE SWITCH | - Depress this switch at the same time with time set
switch to get correct minutes setting.
DYNALERT
SET SWITCH
Depressing this switch first then following the
time set procedure (do not depress time set
switch) will set your alarm. After alarm is set
release switch so the clock will function normally.
ALARM SWITCH | - Depressing this switch causes the alarm to sound
at a preselected time. Relcase switch to shut alarm
off. Alarm will also go off automatically after one
(1) minute if you choose not to release switch.
RADIO SWITCH - Depressing the radio switch will cause the radio to
tum on at the preselected time. Depress switch to
tum the radio off.
t6
COUNTER/TIME
COUNTER SWITCH - Depressing this switch causes the receiver frequen-
cy to be displayed in the receive mode and the
transmitter frequency to be displayed in lhe
transmit mode.
AUTO SWITCH - Depressing this switch causes the time to be
displayed in the receive mode and the trans-
mitter frequency to be displayed in the transmit
mode.
TIME SWITCH - Depressing this switch causes the time to be
displayed continuously.
RECEIVING SSB SIGNALS
There are three types of signals presently used for communications in the
Citizens Band: AM, USB, and LSB. When the MODE switch on your unit is
placed in the AM position, only standard duuble-sideband, full carrier signals will
be detected. An SSB signal may be recognized while in the AM mode by its
characteristic “Donald Duck” sound and the inability of the AM detector to
produce an intelligible output. The USB and LSB modes will detect upper
sideband and lower sideband respectively, and standard AM signals.
SSB reception differs from standard AM reception in that the SSB receiver
does not require a carrier or opposite sideband to produce an intelligible signal.
A single-sideband transmitted signal consists only of the upper or the lower
sideband and no carrier is transmitted. The elimination of the carrier from the
AM signal helps to eliminate the biggest cause of whistles and tones heard on
channels which make even moderately strong AM signals unreadable. Also, SSB
takes only half of an AM channel, therefore two SSB conversations will fit into
each channel, expanding the 40 AM channels to 80 SSB channels. The reduction
in channel space required also helps in the receiver because only half of the noise
and interference can be received with 100% of the SSB signal.
An SSB signal may be received only when the listening receiver is
functioning in the same mode. In other words, an upper sideband signal (USB)
may be made intelligible onty if the receiver is functioning in the USB position.
17
If a lower sideband (LSB) signal is heard when the receiver is in the USB
mode, no amount of tuning will make the signal intelligible. The reason for this
may be understood if you consider that when modulation is applied to the
transmitter's microphone in the USB mode, the transmitter's output frequency
is increased whereas in the LSB mode the transmitter's output frequency is
decreased. The result in listening to the receiver is that when the MODE switch is
in the proper position (either USB or LSB), a true reproduction pf single tone of
modulation will result, and if the tone is increased in frequency (such as a
low-pitched whistle to a high-pitched whistle) you will hear the increase in the
output tone of the receiver. If the incorrect made 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 canno! be made intelligible by
the voice lock control. When listening to an AM transmission, a correct sideband
is heard in either mode since both upper and lower sideband are received.
Once the desired SSB mode has been selected, frequency adjustment may be
necessary in order to make the incoming signal intelligible. the VOICE LOCK
control allows the operator to vary frequency above and below the exact-center
frequency of the received signal. If the sound of the incoming signal is high or
low pitched, adjust the operation of the VOICE LOCK. Consider it as
performing the same function as a phonograph speed control. When the speed is
set too high, voices will be high-pilched and if set too low, voices will be
low-pitched. Also, there is only one correct specd that will make a particular
record produce the same sound that was recorded. If the record is played on a
turntable that rotates in the wrong direction (opposite sideband) no amount of
speed control (VOICE LOCK) will produce an intelligible sound
An AM signal received while listening in ane of.the SSB modes will produce
a steady tone (carrier) in addition to the intelligence, unless the SSB receiver is
tuned to exactly the same frequency by the VOICE LOCK control. For
simphicity it is recommended that the AM modes be used to listen to AM signals.
Section V
Maintenance and Adjustment
The COBRA 2000GTL transceiver is designed spocifically for use as a base
station and may also be used in mobile installation. The use of all solid state
circuitry and light weight result in high reliability. Should a failure occur,
however, replace parts onty with identical parts, Do not substitute. Refer to the
schematic diagram and parts list.
NOTE
IC the performance described in the OPERATION and MAINTENANCE
AND ADJUSTMENT sections is not obtained, review the operating
instructions to insure thal proper procedures were followed. If a
problem still exists, refer to WARRANTY SERVICE INSTRUCTIONS
elsewhere in (his manual.
- FCC WARNING
All transmitter adjustments other than those provided on front panel
by the manufacturer must be made by or under the supervisian of the
holder of an FCC-issued gencral radio-telephone operator's license.
19
Section VI
Appendix
Citizens Band radio operators have largely adopted the “IO-code” for
standard questions and answers. Its use permits faster communications and
better understanding in noisy areas. The following table lists some of the more
common codes and their meanings.
10 CODE
Code Meaning Code Meaning
101 Recciving poorly 10-29 Time is up for contact
102 — Receiving well
103 Stop transmitting 10:30 Does not conform to FCC
104 OK, message received rules
105 — Relay message 10:32 Iwill give you a radio check
106 Busy, stand by 10:33 EMERGENCY TRAFFIC
107 Outof service, leaving air 10-34 Trouhle at this station
10.8 Inservice, subject to call 10:35 Confidential information
109 Repeat message 1036 — Correct time is
10-37 | Wrecker needed at
10-10 — Transmission completed, 10:38 — Ambulance needed at
standing by 10:39 Your message delivered
10-11 Talking too rapidiy
10-12 Visitors present 10-81 Please tura to channel
10:13 Adyise Weather/Road 1042 Traffic accident at
conditions 1043 Traffic Tic up at
10-16 Make pickupat 10-48 Lhave a message for you
10-17 Urgent business 10-45 Al units within range please
10-18 Anything for us? report
10-19 Nothing for you, return to
base 10:50 Break channel
10:20 My location is 10.60 What is next message number?
10-21 Call by telephone 1062 - Unable to copy, use phone
10-22 Report in person to 1063 Net directed to
10-23 Stand by 10464 — Netclar
1024 — Completed last assignment 10465 — Awaiting your next
10:25 Can you contact message/assignment
10-26 — Disregard last information 10-67 Alt units comply
10:27 Yam moving to channel
10-28 — Identify your station 10:70 Fireat
20
10 CODE (Continued)
Code Meaning Code Meaning
10:71 — Proceed with transmission in 1091 Talk closer to mike
sequence 10:93 Check my frequency on this
10-77 — Negative contact channel
10.94 Please give me a long count
10-81 Reserve hotel room tor 10:99 Mission completed, all units
10:82 — Reserve room for secure
10-84 My telephone number is
1085 My addressis 10200 Police needed at
A FEW RULES THAT SHOULD BE OBEYED
1. You are not allowed to carry on à conversalion 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 over-powering them with
illegally amplified transmitter power, or illegally high antennas.
3. You can'tuse CB to promote illegal activities.
4. You are not allowed to use profanity.
5. You may not play music in your CB.
6. You may not use your CB to sell merchandise or professional service.
2