Cobra 150GTL Manual

150GTL ALIGNMENT REVISION: 1.0 BURKE
Page:1 print date: 2/14/06
ALIGNMENT PROCEDURE
MODEL: 150GTL
REVISION: 1.1
DATE: 02/14/06
PREPARED BY: BURKE
Total Pages: 6 pages

150GTL ALIGNMENT REVISION: 1.0 BURKE
Page:2 print date: 2/14/06
150GTL ALIGNMENT INSTRUCTION
1 TEST CONDITION:
1.0. TEST TEMPERTAURE: 77 ±9 °F
1.1. STANDARD DC POWER: 13.8VDC
1.2. STANDARD AUDIO LOADING: 8 Ω
1.3. ANTENNA IMPEDANCE: 50 Ω
1.4. STANDARD REF. MODULATION: AM 30%
FM 2.5KHz
1.5. PULSE GENERATOR: 1µS pulse @ 100mS and 1V peak-to-peak amplitude,
with rise and fall time of less than 10nS.
1.6. TEST EQUIPMENT SETUP AS BELOW:
A. TX test equipment setup:
RF
Wattmeter
Dummy
Load
Modulation
Meter
Power
Supply
150 GTL
Audio
Generator

150GTL ALIGNMENT REVISION: 1.0 BURKE
Page:3 print date: 2/14/06
B. RX test equipment setup:
2.0 MAIN ALIGNMENT
2.1 PLL Alignment
STEP PRESET TO CONNECTIONS ADJUST PROCEDURE
1 RX mode, AM,
28.000MHz Oscilloscope to TP1 T712 Check for range of 0.2 to 7VDC, then set to 2.8V
2 Change to Band D Oscilloscope to TP1 DC level should be < 6V
3 Same as step 1 Oscilloscope to TP2 T713 Adjust for maximum output
4 Same as step 1 Oscilloscope to 4th test
point of CON2 T717 Adjust for maximum output
5 Same as step 1 Frequency counter to
TP3 CT1 Adjust for 17.305MHz (frequency – 10.695)
2.2 Carrier Alignment
STEP PRESET TO CONNECTIONS ADJUST PROCEDURE
1 TX mode, AM,
28.000MHz Frequency counter to TP3 CT2 Adjust for 28.000MHz
Noise Pulse
Generator
150GTL Power
Supply
RF Signal
Generator
AC
VTVM
Oscilloscope
8 ohm Load

150GTL ALIGNMENT REVISION: 1.0 BURKE
Page:4 print date: 2/14/06
3.0 RECEIVER ALIGNMENT
Connect an AC VTVM with 8 ohm load across speaker coil.
Adjust volume control to obtain a suitable indication.
Set generator output low enough to prevent AGC limiting.
Preset controls as follows, unless otherwise noted:
RF Gain maximum, Squelch minimum, NB/ANL off.
STEP PRESET TO CONNECTIONS ADJUST PROCEDURE
1 RX mode, AM
28.000MHz
Output of signal generator to
antenna connector.
Freq. = 28.000MHz, 1KHz 30%
modulation, RF output 1µV
T703, T704,
T705, T706,
T707, T708,
T710
Adjust for maximum signal on
VTVM
2 Same as step 1, squelch to
maximum
Output of signal generator to
antenna connector.
Freq. = 28.000MHz, 1KHz 30%
modulation, RF output 1500µV
RV2 SQUELCH RANGE
Adjust just until squelch opens
3 Same as step 1
Output of signal generator to
antenna connector.
Freq. = 28.000MHz, NO
modulation, RF output 100µV
RV15 SIGNAL METER Adjust for a reading of S-9 on the
analog meter of the radio
4
RX mode, AM,
28.000MHz,
NB/ANL switch
set to NB/ANL
Output of signal generator and
noise pulse generator to antenna
connector.
Freq. = 28.000MHz, 1KHz 30%
modulation, RF output 1µV.
Oscilloscope to collector of Q6
T701 NOISE BLANKER Adjust for maximum amplitude
on oscilloscope
5 RX mode, FM,
28.000MHz
Output of signal generator to
antenna connector.
Freq. = 28.000MHz, 2.5KHz
deviation, RF output 1µV
T702 Adjust for maximum signal on
VTVM
4.0 TRANSMITTER ALIGNMENT
Maintain a 50 ohm 25 watt dummy load on the antenna connector for the following steps.
Preset controls as follows, unless otherwise noted:
RF Power set to HI, Mic Gain to minimum.
STEP PRESET TO CONNECTIONS ADJUST PROCEDURE
1 TX mode, AM,
29.700MHz RF wattmeter to antenna connector
T718, T719,
T720, T721,
T722, T723 Adjust for maximum RF output
2 Same as step 1 Same as step 1 L21 RF POWER - HI Adjust for 13-17 watts on all
bands
3 Same as step 1,
Power switch to LO Same as step 1 RV9 RF POWER - LO Adjust for 4 watts

150GTL ALIGNMENT REVISION: 1.0 BURKE
Page:5 print date: 2/14/06
STEP PRESET TO CONNECTIONS ADJUST PROCEDURE
4 TX mode, AM,
29.700MHz RV1 RF POWER METER
Adjust for a reading of S-9 on the
analog meter of the radio
5
TX mode, AM,
29.700MHz
Mic Gain to
maximum
Modulation meter to
antenna connector.
Insert a 1KHz, 30mV
signal to microphone
input.
RV12 AMC CONTROL - HI Adjust for 90% modulation on
all bands
6 Same as step 5,
Power switch to LO Same as step 5 RV4 AMC CONTROL - LO
Adjust for 90% modulation on
all bands
7
TX mode, FM,
29.700MHz
Mic Gain to
maximum
Same as step 5 RV5 DEVIATION LIMITER
Adjust for 2.5KHz deviation
8
TX mode, AM,
Power switch to LO,
Mic Gain to
minimum, S/RF
switch set to CAL
Connect a 100 ohm
non-inductive dummy
load to the antenna
connector
RV17
SWR METER
Adjust SWR Cal knob so analog
meter on radio goes to CAL
mark. Then set S/RF switch to
SWR and adjust RV17 for an
SWR reading of 2 on the analog
meter of the radio.
9
TX mode, AM,
Power switch to LO,
Mic Gain to
minimum
Short the antenna output
to ground
RV3 (located
on back of
front panel)
ANTENNA LIGHT
Adjust RV3 just until the
antenna light comes on

150GTL ALIGNMENT REVISION: 1.0 BURKE
Page:6 print date: 2/14/06

150GTL ALIGNMENT REVISION: 1.0 BURKE
Page:7 print date: 2/14/06
REVISION HISTORY
1.0 – Initial release
1.1 – Added section Step 9 in Section 4