| Pin | Description |
|---|---|
| 1 | Ground |
| 2 | Microphone |
| 3 | TX Key (Connect to Ground) |
| 4 | Speaker (Connect to Ground) |
DX2547 Schematic Diagram
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 (TR17) with an 2SC2999
(or similar low noise and high gain transistor) to achieve this improved signal to noise
ratio.
Re-Adjust L5 and L6
The gain will improved with more than 6dB with the same signal to noise ratio.