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President J.F.K. CB-Radio


ALIGNMENT PROCEDURE


RECEIVER PORTION


Test equipment required:
Power Supply: 13,8 VRF Signal GeneratorDummy Load 8 ohmOscilloscope
AF VTVM

Preparation alignment:
MIC GAINMax.
S/RF-SWR-CALS/RF
NB/ANLOff
RF SSGModulation: 30% AM 1000Hz
StepConditionAdjustmentProcedure
1CH: 19, BAND: MID
VOL: Max.
SQ: Min.
MODE: AM
L7, L6
L5, L4
L1
Connect RF SSG to Ant. jack and AC Voltmeter to Ext. Speacer. Then adjust coils for maximum reading on AC Voltmeter.
2VOL: Max.
SQ: Min.
MODE: AM
L2
L3
Adjust L2 for maximum output of noise level in LOW BAND CH 1. Then adjust L3 by same way of adjustment for L2 in HIGH BAND CH 40. Ant then adjust L2 by turn CW in LOW BAND CH 1 so that the same noise level of adjustment for L3.
3CH: 19, BAND: MID
VOL: Max.
SQ: Max.
MODE: AM
VR2Set the output level of RF SSG to 1000uV. Adjust VR2 for 2 V output reading on AC Voltmeter.
4CH: 19, BAND: MID
VOL: Max.
SQ: Min.
MODE: AM
VR1Set the output level of RF SSG to 100uV. Adjust VR1 so that the needle of built-in signal meter point "S-9".
5CH: 19, BAND: MID
VOL: Max.
SQ: Min.
MODE: FM
L801Adjus VOL to obtain 2 V output on AC Voltmeter. Set the level of RF SSG to 100uV. Adjust L801 for maximum reading on AC Voltmeter.


Improved receive gain

Quieting of AM reception and improving gain of incoming signals is a common request from radio operators. In the first stages of the HF input 2SC1674 transistor can be found. This transistor is responsible for the amplification of a small detected signals. A problems exist if the transistor itself is noisy as is such the case of the 2SC1674 when compared to other low noise packages. Along with the amplification of the incoming signals is transistor noise. Replacement of this transistor with a higher gain, lower noise transistor greatly improves the signal to noise ratio of your receiver.
We will use an 2SC2999 transistor that has higher gain lower noise characteristic. Replace the 2SC1674 (Q2) with an 2SC2999 (or similar low noise and high gain transistor) to achieve this improved signal to noise ratio.
Re-Adjust L1 and L2
The gain will improved with more than 6dB with the same signal to noise ratio.