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Ham International III

CHASSIS PTBM133A4X


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Software for PTBM133A4X



Circuit Theory

Oscillator frequency
VCO-frequency = Oscillator frequency (Q2) - FIN
VCO-frequency = 20.105MHz - 2.55MHz = 17.555MHz @ Ch.1 Band 40
Output from BPF (T1 / T2) = Oscillator frequency (Q2) + VCO-frequency
Output from BPF (T1 / T2) = 20.105MHz + 17.555MHz = 37.660MHz @ Ch.1 Band 40
RX and TX frequency = Output from BPF (T1 / T2) - IF-frequency
RX and TX frequency = 37.660MHz - 10.695MHz = 26.965MHz @ Ch.1 Band 40

Programming Chart for PLL02A
BandCh.FINP0P1P2P3P4P5P6P7P8
4012.55MHz111111XXX
4022.54MHz011111XXX
4032.53MHz101111XXX
4042.51MHz110111XXX
4052.50MHz010111XXX
-
40402.11MHz110010XXX
-
-80XXXXXXXX001
-40XXXXXXXX001
40XXXXXXXX110
80XXXXXXXX110
120XXXXXXXX110


Adjustment

Reading PointAdjustmentDescriptionValue
PLL
TP2VCO-Block CoilVCO Voltage4 Volt @ 27.185MHz
OSCILLATOR
U1 Pin 3CheckReference Oscillator10.240MHz
TP1CT1RX AM -80 Band19.880MHz
TP1CT2RX AM 40 and -40 Band20.105MHz
TP1CT3RX AM 80 Band20.330MHz
TP1CT4RX AM 120 Band20.555MHz
TP1CT5RX LSB 40 Band20.1035MHz
TP3CT7TX AM10.695MHz
TP3CT8RX LSB10.692MHz
AdjustmentDescriptionValue
RECEIVER
T8RF Input
T9RF Input
T10RF Input
T111. IF10,7MHz
T121. IF10,7MHz
T13AM IF455kHz
T14AM Detector455kHz
T6SSB IF455kHz
T7SSB Detector455kHz
T18FM Discriminator455kHz
RV6SSB AGC
RV10Squelch
TRANSMITTER
T1PLL Output to Converter37.660 - 38.100MHz for CEPT
T2PLL Output to Converter37.660 - 38.100MHz for CEPT
T3Transmitter Output AM26.965 - 27.405MHz for CEPT
T4Transmitter Output AM26.965 - 27.405MHz for CEPT
T5Transmitter Output AM26.965 - 27.405MHz for CEPT
CT6Transmitter Output USB/LSB26.965 - 27.405MHz for CEPT
RV2Bias Q8
RV11AM/FM Output Power10 Watt
RV3 and RV9SSB Modulation18 Watt p-p
RV1FM Modulation+/- 2kHz
RV12AM Modulation90%
RV5Carrier at SSBAdjust for minimum carrier leakage
METER
RV4RF Power Meter10 Watt
RV7RF S-MeterSSB (USB/LSB)
RV8RF S-MeterAM/FM

Microphone Connection

PinDescription
1Microphone
2Ground
3Speaker (Connect to Ground)
4TX Key (Connect to Ground)

COMPONENTS

PTBM133A4X Schematic Diagram
Frequency List for HAM International Multimode 3
VCO Block
2SC1969 Finale Transistor
2SC2166 Driver Transistor
2SC1675 RF Transistor
AN7140 Audio Power Amplifier
BA403 FM IF-Amplifier and Discriminator
AN612 Balanced Modulator
TA7310P Oscillator, Mixer and Amplifier
PLL02A PLL Frequency Synthesizer

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 2SC1675 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 2SC1675 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 2SC1675 (Q16) with an 2SC2999 (or similar low noise and high gain transistor) to achieve this improved signal to noise ratio.
Re-Adjust T8 and T9 / T10
The gain will improved with more than 6dB with the same signal to noise ratio.