Cobra 148 Alignment

Table of Contents

Alignment for the Cobra 148GTL 148GTL-ST 148NW-ST

VCO

Step	Preset To	Connections	Adjust	Procedure
1	RX mode, AM CH 1	DC voltmeter to TP9	L19	Adjust for 3.2V +/-0.1V Check CH40 = 4.2V +/-0.2V
2	RX mode, AM CH19	O’scope to TP10	L21	Adjust for max output
3	Same as step 2	Oscope to TP1	L20	Adjust for max output
4	RX mode AM CH19 Voicelock center	Freq counter to TP1	L23	Adjust for 34.985MHz
5	RX Mode LSB voicelock center	Freq Counter to TP1	L22	adjust for 34.9835MHz
6	RX mode USB CH19 voicelock center	Freq Counter to TP1	L59	Adjust for 34.9865MHz

Carrier

Step	Preset To	Connections	Adjust	Procedure
1	TX mode AM CH19	Freq counter to cathode of D17 Disconnect TP7 & TP8	L31	Adust for 7.8MHz then re-connect TP7 & TP8
2	RX mode LSB CH19	Freq counter to TP14	L30	Adjust for 7.7985MHz
3	TX mode USB CH19	Freq counter to TP14	CT2	Adjust for 7.8015MHz

Receiver

Connect AC VTVM across speaker coil Adjust colume control to obtain a suitable indication set generator output low enough to prevent AGC limiting preset controls as follows unless otherwise noted: RF Gain Maxiumum, Voicelock center, Squelch min, NB/ANL off, Tone normal

Step	Preset To	Connections	Adjust	Procedure
1	RX mode CH19 USB	Output of signal gen through 0.01uF to TP16 (TR15 emitter) Freq = 7.8005MHz NO Modulation RF output 200uV	L7,L8,L9,L10,L12,L14	Adjust for max output
2	RX mode CH19 AM	Ooutput of signal gen though 0.01uF to TP15 Freq = 455KHz 1KHz 30% modulation EF output 100oV	L15,L13,L3	Adjust for max output
3	RX mode CH19 AM	output of signal gen to antenna input FREQ = 27.185 1KHz 30% modulation RF output 1uV	L4,L5,L6	Adjust for max output
4	RX mode CH19 AM NB/ANL switch set to NB	Output of signal gen to antenna input FREQ 27.185 1KHz 30% mod rf output 1uV oscope to TP17	L1,L2	NB adjust for max pulse amplitude on scope
5	RX mode CH19 AM SQL set to Max	output of signal gen to ant input FREQ 27.185 1KHz 30% mod RF output 1800uV	VR3	SQL range adjust until audio just appears
6	RX CH19 AM	output of signal gen to ant input FREQ 27.185MHz 1KHz 30% mod RF output 100uV	VR1	adjust for reading of S9 on S-Meter
7	RX CH19 USB	output of signal gen to ant input FREQ 27.186 no modulation rf output 100uV	VR2	adjustfor reading of S-9 on the S-Meter

Transmitter

Maintain a 50ohm 25 watt dummy load on the antenna input for the following

Step	Preset To	Connections	Adjust	Procedure
1	TX mode CH19 Dynamike min	RF wattmeter to antenna input	L47,L48,L46,L45,L38	Adjust for maximum RF output
2	Same as step 1	Specturm analyzer to antenna input	L36	Adjust for minimum 54MHz 2nd harmonic
3	TX mode CH19 USB dynamike Minimum	RF wattmeter to antenna input	VR7	Carrier Balance Adjust for min RF output
4	same as step 3	Insert ammeter at TP8	VR9	DRIVER BIAS adjust for 25mA
5	same as step 3	Insert ammeter at TP7	VR8	FINAL BIAS Adjust for 50mA
6	TX mode CH19 USB dynamike Maximum	RF wattmeter to antenna input, insert a two tone 500mV signal into microphone input	VR11	SSB ALC Adjust for 12 watts PEP RF output
7	TX mode CH19 AM Dynamike Minimum	RF wattmeter to antenna input	VR10	AM CARRIER Adjust for 4 watts RF output
8	same as step 7		VR6	RF Power Meter adjust so the needle of the CB’s analog meter is at the border between the green and red zone
9	same as step 7	Freq counter to antenna input	VR5	TX CARRIER FREQ adjust for 27.185MHz
10	TX mode CH19 AM Dynamike maximum	Modulation meter to antenna input insert 1KHz 50mV signal to microphone input	VR501	AMC CONTROL Adjust for 100% modulation
11	CH19 AM	remove dummy load connect a 100ohm load to the antenna input use built in SWR meter to check the SWR	VR12	SWR Meter adjust for a SWR reading of 2