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President George 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
ClarifierCenter
Frequency27.185 MHz

StepConditionAdjustmentProcedure
1AM
60% Mod.
L17 L2 L6 L7 L11 L12 L13Adjust for maximum reading on the AF VTVM
2FM
1.2 kHz Dev.
L16Adjust for maximum reading on the AF VTVM
3AM
No Mod.
VR4SSG: 40dB (50uV) Adjust "9" just light on
4AM
No Mod.
VR2SSG: 66dB (1mV) Just apper AF level
5USB
No Mod.
L15 and L14Adjust for maximum reading on the AF VTVM
6USB
No Mod.
VR3SSG: 40dB (50uV) Adjust "9" just light on
7USB
No Mod.
VR1SSG: 66dB (1 mV) Just apper AF level
8USB
No Mod.
L1Connect Oscilloscope to TP4. Set Oscilloscope to DC range and adjust to reach max. reading.
9AM
26.065 MHz
60% Mod.
CheckSSG: 10dB
More than 20 dB SINAD
10AM
28.755 MHz
60% Mod.
CheckSSG: 10dB
More than 20 dB SINAD



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 (Q8) 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 Q8 operates at VCE= 6Volt and IE= 2,5mA. We will use an 2SC2999 transistor that has higher gain and lower noise characteristic. Replace 2SC1674 (Q8) 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.