Simple Cable TV Amplifier Circuit

Cable TV channels use the thin wires to pass through.

As these signals go further they start getting weaker.

Similar to a little radio where a cable TV amplifier circuit boosts the signals strength.

This makes it more possible, that viewers may get a clear signal.

Circuit Working:

Parts List:

This RF amplifier circuit is particularly developed for cable TV applications and can be easily installed between two coaxial wires.

Both input and output impedances are designed to work with 75Ω cables.

The T1 transistor is used in the main amplifier and transistor T2 acts as an emitter follower.

The feedback bias is calculated by 820Ω and 75Ω.

The total gain of this cable TV amplifier is 22dB.

Because of the inherent high frequency limitations of transistors up to 2GHz the amplifier works up to 150MHz.

Enclose it in a metal container and use 75Ω coaxial wires.

This cable TV amplifier circuits overall current usage is about 20mA.

Formula:

A key component of circuits with vast bandwidth frequencies is the transistor gain bandwidth ratio (GBW) which is easily calculated using the below mentioned process.

GBW = Av ​× f − 3dB​

where,

• GBW is the gain bandwidth product
• Av​ is the voltage gain of the transistor
• f−3d bandwidth of the circuit or frequency at which the gain drops by 3dB.

According to this formula a rough estimation of a transistors ability in amplifying signals at higher frequencies is obtained by multiplying its gain by the frequency at which the gain begins to drop off or the -3dB point for a specific transistor with a voltage gain of Av.

How to Build:

To build a Simple Cable TV Amplifier Circuit following steps are mentioned below which are required for connections:

Connect the parts:

• As shown in the circuit diagram above connect all required components.

Design of Circuits:

• See the circuit diagram for the cable TV amplifier.
• As described in the circuit design place the T1 and T2 transistors on the PCB or protoboard.
• As shown in the diagram connect the resistors and other parts.

Soldering:

• Use a soldering iron to carefully solder the components onto the board.
• To avoid short circuits always check the connections twice.

Input and output connections:

• Connect the input and output coaxial cables to their proper spots on the circuit.
• Ensure the coaxial cables are 75Ω type.

Accommodation:

• Enclose the completed circuit in a frame of metal to prevent outside influence.
• To prevent overheating check that that the housing has enough airflow.

Power Supply (where applicable):

• If the amplifier requires a power supply than connect it according to the schematic
• Ensure that the voltage and current requirements are satisfied as per ones need.

Testing:

• Turn ON the amplifier and test it using a signal source such as a cable television supply.
• To check performance use suitable testing equipment such as an oscilloscope or signal analyzer.

Modification:

• The biasing resistors 820Ω and 75Ω is adjusted to give the required feedback bias needed to enhance amplifier performance.

Last Verifications:

• Lastly confirm that the amplifier produces the required amount of gain and functions within the specified frequency range.

Safety precautions:

• While working with electrical components it is necessary to follow every safety rules.
• Check all of the connections verify there are no loose wires or soldering crossings.

Note:

Keep in mind while building electrical circuits it requires both an understanding of electronics and the knowledge of the proper precautions to follow.

One needs to get help from an experienced person or do contact with an electronics expert if anyone lacks skill with electronic building.

Conclusion:

Simple cable TV amplifier circuits play an important role for maintaining signal quality and ensuring that viewers get clear and accurate television signals especially when cable signals have to travel great distances or pass through several distribution network separation points.

References:

Datasheet 2SC4308