President James CB-Radio

ALIGNMENT PROCEDURE

RECEIVER PORTION


Test equipment required:
Power Supply: 13,2 VSINAD MeterOscilloscope
AM/FM SSG(AM: 1 kHz 60% Mod.)(FM: 1 kHz 1.2 kHz Deviation)

Preparation alignment:
NB/ANLOff
HI CUTOff
SQUELCHCounter clockwise
VolumeClockwise
RF GainClockwise
Frequency27.185 MHz

StepConditionAdjustmentProcedure
1AM
60% Mod.		L2 L11 L12 L13 L17 L18Adjust for maximum reading on the AF VTVM
2FM
1.2 kHz Dev.		L21Adjust for maximum reading on the AF VTVM
3AM
No Mod.		VR2SSG: 100uV
Adjust "9" just light on LCD-meter
4AM
No Mod.		VR3SSG: 100uV
Adjust "9" just light on External Meter
5AM
No Mod.		VR1SSG: 66dB (1mV) Just apper AF level

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 (Q11) 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.

The transistor Q11 operates at VCE= 6Volt and IE= 2,5mA. We will use an 2SC2999 transistor that has higher gain and lower noise characteristic. Replace 2SC1674 (Q11) with 2SC2999 (or similar low noise and high gain transistor) to achieve this improved signal to noise ratio.
Re-adjust L2.
The gain will improved with more than 6dB with the same signal to noise ratio.