Booster Circuit for Cable Radio

Anyone having problem getting radio signal from cable?

Maybe this post for Booster Circuit for Cable Radio can help which is also called cable radio amplifier.

This thing make signal strong when going through cable.

Cable company give many channels but sometimes signal is not good because of too much distance or interference.

Because of this the radio sound bad or is not clear.

If uses cable booster and that is maybe radio signal become better and stronger.

Circuit Working:

Parts List:

This circuit help small VHF FM radio get signal from cable TV wire.

It uses two times signal boost with simple RF parts called BF199 transistors.

It work like antenna amplifier which is almost a same idea.

But no antenna is used here we must connect input to cable wire and not to antenna.

Output side have special part in tuned circuit for matching with 1/4λ antenna but not to coax connector there.

One small antenna of vertical type send out stronger cable signal.

If we adjust trimmer C8 in correct way, then radio can catch signal from 3 meter away.

We can build circuit on test board but RF is very sensitive.

So better to use PCB layout for good working.

Wiring is not hard with big ground area is already there in design.

Like in diagram one part C7 must connect direct to coil L1 tap.

To make coil take 8mm pencil and wrap 3 turns of 1mm wire with no plastic enameled copper because this coil is very important.

From coax connector K1 to board keep wires short.

Long wire can make signal bad or make circuit unstable.

Also put whole board inside metal box to stop outside noise.

Use 9V battery or small power supply to about 2.5 mA to give power to this booster.

Formulas:

For cable radios we must build booster circuit to make sure RF signal go strong and clear through cable to the radio receiver.

When making this kind of booster circuit we must remember some important parts and one main formula.

Important formula is for gain of Low Noise Amplifier (LNA) and this tell how much signal will get amplified.

Formula is:

GdB = 10 × log10(G)

where:

• GdB is the gain in decibels (dB)
• G is the voltage gain of the LNA

The gain (G) usually depends on what resistors and capacitors we use in the LNA circuit.

Many LNA chips already show gain in their datasheet.

How it works:

Mostly we use LNA like Mini Circuits MAR-6.

It give good gain and very low noise which is good for cable radio signal.

When making cable radio booster we must choose right LNA and also use impedance match and bandpass filter if needed.

By boosting signal and reducing noise this circuit helps make radio sound more clear and stable.

How to Build:

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

Make the PCB Ready:

• Use the circuit design to put parts on the PCB board.
• Start with the small parts first and then solder all parts one by one on the PCB.

Connect the Parts:

• Join the parts same like the PCB layout and wiring diagram.
• Be sure capacitors, transistors and coaxial parts are in correct direction.

Make the L1 Coil:

• Take a pencil of 8mm wide and roll 3 turns of 1mm thick enameled copper wire.
• This is our L1 coil.
• Now solder L1 to PCB as shown in diagram.

Adjust the Circuit:

• Use trimmer capacitor C8 to fine tune the signal.
• If we have oscilloscope or multimeter use that to adjust.
• Turn C8 slowly to get strong signal from antenna.

Add Power:

• Use 9V battery or small regulated power supply.
• Connect it to the booster circuit.

Close the PCB:

• Put the finished PCB inside a metal box.
• This protects the circuit from outside noise.
• Be sure coaxial connector is placed correct on the box.

Test the Circuit:

• Connect a small VHF FM radio near the antenna.
• Turn ON the circuit.
• Radio should now receive signal from local cable network.

Adjust More If Needed:

• If signal is not strong then we can make small changes in the circuit.
• Try to get best sound and signal.

Be Careful:

• Always be safe while working with electronic parts.
• Check all wires and connections before turning power ON.
• If we do not understand well better to ask for expert help.

Conclusion:

Booster Circuit for Cable Radio use transistors, resistors, capacitors and coil to make signal strong.

Impedance matching also helps to send signal better between parts.

Cable radio booster helps make RF signal from cable more strong and clear.

References:

Datasheet BF199