Cobra 150GTL Alignment Procedure

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

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

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

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

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

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