Sommerkamp TS360 AM/SSB CB-Radio

Block Diagram

Adjustment

Test equipment required:
Power Supply: 13,8 VFrequency CounterDummy Load 50 ohmOscilloscope
RF Power MeterDC AmperemeterRF SSGAF SSG

Preparation alignment:
FineMid.
ClarifierMid.
SQ GAINMax.
AF GAINMax.
RF GAINMax.
MIC GAINMax.
NB/ANLOff
MID Band, Ch. 19Frequency: 27.185MHz
Reading PointConditionAdjustmentProcedure
PLL
IC2 Pin 8-Check10.2400MHz
TP1RX AML14Maximum on Oscilloscope
TP9RX AML13VCO Coil - 4 Volt
RECEIVER
RX USBL10 L9 L8RF
RX USBL7 L6 L5 L4 L3IF 7.8MHz
TP6RX AML1 L2Noise Blanker
TRANSMITTER
TP9 (+) TP8 (-)TX USBVR810mA
TP9 (+) TP7 (-)TX USBVR950mA
TX USB/LSBVR5Modulator Balance
TX AML26Maximum (TX-Mixer input - 7.8MHz)
TX AML27Maximum (TX-Mixer input - RF)
TX AML28Maximum (TX-Mixer output)
TX AML29Maximum (TX-Mixer output)
TX AML56Maximum

Microphone Connection

PinDescription
1Microphone
2Microphone Ground
3Speaker/TX Ground
4Ground
5TX

COMPONENTS

MB8719 PLL Frequency Synthesizer
S042P Duble Balanced Mixer
AN612 Balanced Modulator (SSB Modulator)
TA7222AP Audio Power Amplifier
2SC1969 RF Finale Transistor

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 (TR9) with an 2SC2999 (or similar low noise and high gain transistor) to achieve this improved signal to noise ratio.
Re-Adjust L10 and L9
The gain will improved with more than 6dB with the same signal to noise ratio.