Cable TV Amplifier Circuit uses small wire to send signal.
When signal goes far it become weak.
Like small radio, cable TV amplifier make signal strong again.
This helps people get better and clear picture.
Circuit Working:
Parts List:
| Component | Quantity |
|---|---|
| Resistors (All resistors are 1/4 watt) | |
| 680Ω | 1 |
| 820Ω | 1 |
| 75Ω | 1 |
| 100Ω | 1 |
| Capacitors | |
| Ceramic 0.01μF | 1 |
| Ceramic 0.0022μF | 2 |
| Semiconductors | |
| Transistors 2SC4308 | 2 |
| Connectors | |
| TV input | 1 |
| TV output | 1 |
This RF amplifier circuit is made special for cable TV use.
It can put easy between two coaxial wire.
Input and output both work good with 75 ohm cable.
T1 transistor is used in main amplifier part and T2 transistor work like emitter follower.
Bias get by 820 ohm and 75 ohm resistor.
Total gain of this amplifier is 22 dB.
Because transistor can not work with very high frequency which is only up to 2 GHz then this circuit works good till 150 MHz only.
Better to put in metal box and use 75 ohm coaxial wire only.
This amplifier uses around 20mA current.
Formula:
In high frequency circuit important thing is transistor gain bandwidth product (GBW).
We can find GBW by this formula:
GBW = Av × f−3dB
where:
- GBW is gain bandwidth
- Av is transistor voltage gain
- f−3dB is frequency where gain become 3dB lower
This formula give idea for rough calculations.
How to Build:
To build a Cable TV Amplifier Circuit following steps are mentioned below which are required for connections:
Design of Circuit:
- Check diagram for cable TV amplifier.
- Put T1 and T2 transistor on PCB or breadboard like shown.
- Connect resistors and other parts same like diagram.
Soldering:
- Use soldering iron and carefully solder all parts on board.
- Always check two times to stop short circuit.
Input and Output:
- Connect input and output coaxial cable to right place on circuit.
- Use only 75Ω coaxial cable for good work.
Enclosure:
- Put full circuit inside metal box to block outside signal.
- Be sure the box have some airflow so it does not get too hot.
Power Supply (if needed):
- If amplifier need power then connect it same like shown in diagram.
- Be sure voltage and current is correct for this circuit.
- Switch ON amplifier.
- Test it with cable TV signal.
- Use tools like oscilloscope or signal tester to see if it works good.
Change and Adjust:
- The resistors 820Ω and 75Ω give feedback bias.
- Can adjust them to make amplifier work better.
Final Check:
- At end be sure amplifier gives right gain and work in correct frequency range.
Safety Rules:
- Always follow safety rules when working with electric things.
- Check all wires and solder and be sure nothing is loose or touching wrong.
Note:
- Making circuit need both skill and care.
- If anyone do not know about electronics well then ask for help from experienced person or expert.
Conclusion:
This Cable TV Amplifier Circuit help keep signal strong and clear.
This circuit is good for better TV picture when signal is weak.