|
|
| Ponto de teste | Ajustar | Descrição | Valor |
|---|---|---|---|
| OSCILLATOR | |||
| TP9 | L19 | VCO Coil | |
| TP1 | AM | ||
| TP1 | USB | ||
| TP1 | LSB | ||
| TP1 | L20 | AM | Maximum |
| TR20 Emitter | L21 | AM | Maximum |
| TP3 | CT2 | Carrier frequency | 7.800MHz |
| L48 | Carrier frequency | Maximum | |
| L47 | TX Mixer frequency | Maximum | |
| TP10 | |||
| RECEIVER | |||
| L4 L5 L6 | RF | ||
| L7 L8 L9 L10 | 1st. IF | ||
| L12 L13 L14 L15 | SSB IF | ||
| L3 | AM IF | ||
| L1 L2 | NB/ANL IF | ||
| Internal S-Meter | VR1 | AM | |
| Internal S-meter | VR2 | SSB | |
| TRANSMITTER | |||
| TP8 | VR9 | Driver Bias | 10mA |
| TP7 | VR8 | Finale Bias | 100mA |
| L46 L45 L44 L38 | |||
| VR4 | Modulator Balance | ||
| VR10 | AM Power | 10 Watt | |
| VR11 | SSB Power | 20 watt p.e.p | |
| Internal Power Meter | VR6 |
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 (TR14) with an 2SC2999
(or similar low noise and high gain transistor) to achieve this
improved signal to noise ratio.
Re-Adjust L4 and L5
The gain will improved with more than 6dB with the same signal to
noise ratio.