Simple Booster Circuit for Cable Radio

Did anyone suffer from trouble receiving radio signals through the cable connection?

A cable booster also referred to as a cable radio amplifier would possibly be useful.

The impulses passing through the cable lines are strengthened by this electrical circuit.

Many channels are available through cable companies but sometimes interference or lengthy distances cause the quality to drop.

This may cause the radio to sound uncertain or confused.

One may enjoy great received radio signals on the cable connection and increase the signal power by using a cable booster.

Circuit Working:

Parts List:

This circuit allows a portable VHF FM radio to receive signals from the local cable network.

With its two stage of amplification using common RF transistors BF199 the cable booster is similar to an antenna amplifier in both design and features.

Instead of using an antenna in this design the input should be connected to the cable connection.

The output has a tuned circuit that acts as impedance matching for a 1/4λ-antenna but however it clearly lacks a coaxial connector.

The vertical antenna generates an amplified cable signal that is easily picked up by a portable receiver within three meters when the trimmer C8 is properly adjusted.

Although building the circuit on a prototype board is possible due to the essential sensitivity of RF circuits it would be wise to use the supplied PCB layout for best results.

Essential connections remain simple throughout the design stage and a large ground level is included.

For example as seen in the circuit diagram capacitor C7 needs to be connected straight to the tap on L1.

An 8 mm diameter pencil is wound around three turns of 1 mm enameled copper wire to create the air cored coil which is an essential component of the design.

The connecting wires from coax connector K1 to the PCB should be as short as possible in order to avoid signal interference and most likely oscillation problems.

Also it is important that the PCB should be enclosed in a metal shell.

A 9V battery or a small regulated mains power supply with an average current usage of about 2.5 mA is used as the cable boosters power source.

Formulas:

For cable radios a booster circuit requires to be constructed to guarantee that the RF signal carries across the cable with sufficient strength and clarity to reach the receiver.

When designing a booster circuit of this type keep in mind the following essential components and basic formula.

The key formula for the booster circuit is the Low Noise Amplifiers (LNA) gain which regulates the signal amplification.

G_dB ​= 10log_{10 ​^(G)}

where:

• G_dB​ is the gain in decibels (dB).
• G is the voltage gain of the LNA.

he gain G of an LNA usually depends by the resistors and capacitors used in its construction.

The gain information is found in the datasheet for many standard LNAs.

The formulas working:

Usually a booster circuit uses a commercial LNA such as the Mini Circuits MAR 6 that has the proper gain and low noise figure requirements for cable radio frequencies.

In the design of a cable radio booster circuit the correct LNA must be selected and an impedance matching network and bandpass filter can both be included.

By successfully increasing the RF signals and lowering noise the booster circuit improves the clarity and quality of reception and allows for a steady supply of cable radio signals to the receiver.

How to Build:

Building a Simple Booster Circuit for Cable Radio includes the below mentioned steps:

Get the PCB ready:

• Using the above circuit design as instructions arrange the components on the PCB.
• Start with the lowest circuit component solder the components onto the PCB.

Connect the Components:

• To connect the components according to the PCB design and the schematic.
• Verify that the capacitors and transistors with coaxial connections are positioned correctly.

Get the L1 inductor ready:

• A pencil with an 8mm diameter should be wound around three turns of 1 mm enameled copper wire.
• Solder L1 to the circuit as shown by the circuit diagram.

Adjust the Circuit:

• To fine tune the circuit adjust trimmer capacitor C8.
• If there is an oscilloscope or multimeter one can use it.
• Adjust for best results ensuring the antenna releases the enhanced cable signal.

Connect the power source:

• Add a regulated mains power supply or a 9 V battery to the circuit.

Close the PCB:

• To protect the PCB from external damage place it within the metal enclosure.
• Make that the enclosures coaxial connector is positioned correctly.

Check the circuit:

• A portable VHF FM radio is connected to the circuit through a cable.
• Verify that the radio can receive local cable network stations after switching the circuit ON.

Modify if necessary:

• Adjust the circuit as needed to get maximum efficiency.

Be aware:

• Always remember to take safety precautions while dealing with electronic components and be sure all connections are safe before turning ON the power.
• If anyone is unfamiliar with electronics or confused consider seeking help from an expert.

Conclusion:

Transistors, resistors, capacitors and inductors are often included in the Simple Booster Circuit for Cable Radio in a particular way to achieve the required amplification.

Features like impedance matching can also be included to enhance signal transmission between different system parts.

The radio frequency (RF) signals are connected to cable broadcasting and are especially enhanced by a cable radio booster circuit.

This kind of booster is used to enhance cable radio stations reception quality lowering the chance of signal interference and enabling listeners to experience higher sound quality.

References:

Datasheet BF199