Simple FM Radio Receiver Antenna Booster Circuit

Do you ever get static on your favorite radio stations?

This guide shows you how to build a signal booster for your FM radio antenna.

Radio signals travel through the air, and sometimes they can be weak especially if you live far from the radio station.

This circuit helps make those weak signals stronger so your radio can pick them up better and you hear less static.

Circuit Working:

Parts List:

This budget friendly FM radio receiver antenna enhancer employs the BF324 TO92 style PNP transistor in a grounded base configuration.

The circuit functions as a signal booster particularly beneficial for VHF receivers experiencing low sensitivity in their front end, such as various vacuum tube models and army surplus types.

The preamplifier covers a frequency range approximately from 75MHz to 150MHz.

The two inductors within the circuit are crafted at home.

L1 comprises 10 turns of 24SWG enameled copper wire with a 3mm internal diameter and no core.

Inductor L2 consists of 13 turns of the same wire with a 5mm internal diameter and no core.

A construction tip:

Wind the inductors closely using 3mm and 5mm drill bits as temporary formers, respectively.

The preamplifier prototype proved successful when used with an 88 to 108 MHz FM broadcast receiver and a 2 meter VHF ham receiver.

Drawing around 2.5mA from a 5V supply the preamplifier demonstrates efficient performance.

Formulas:

Enhancing the signal to noise ratio (SNR) of an FM radio receiver by the amplification of received radio frequency signals is known as antenna signal booster.

Here is a fundamental formula and some things to think about while creating an FM radio receiver antenna booster

The gain equation, which establishes the amplifiers gain and how much it amplifies the input signal, is a crucial formula for the LNA:

G = 20log₁₀ ​(A_v​)

where:

• G is the gain in decibels (dB).
• A_v is the voltage gain of the amplifier.

How formula works:

Using a commercial LNA made for FM radio frequencies, such the Mini Circuits MAR 6 or something similar, which has a high gain and low noise figure appropriate for FM reception, is a typical arrangement.

In order to design an FM radio receiver antenna booster, the right LNA with the required gain and low noise figure must be chosen.

A bandpass filter may also be integrated for frequency selection.

The booster improves the clarity and decreases interference in FM radio reception by efficiently boosting the antennas weak signals.

How to Build:

To build the FM radio receiver antenna booster with the BF324 TO92 transistor follow below steps:

Prepare the Inductors:

• Wind 10 turns of 24SWG enameled copper wire on a 3mm diameter temporary former no core to create inductor L1.
• Wind 13 turns of the same wire on a 5mm diameter former no core to create inductor L2.

Assemble the Circuit:

• Refer to the circuit diagram for the grounded base configuration using the BF324 TO92 transistor.
• Connect the inductors L1 and L2 as specified in the diagram.
• Add the required resistors, capacitors and other components to complete the circuit.

Use Drill Bits as Formers:

• Close wind the inductors by wrapping the wire tightly around the 3mm and 5mm drill bits as temporary formers.

Soldering:

• Carefully solder all the components onto the PCB or breadboard according to the circuit diagram.
• Double check for any loose connections or solder bridges.

Connect Power Supply:

• Connect a 5V power supply to the circuit.

Testing:

• Test the preamplifier with an 88 to 108 MHz FM broadcast receiver and a 2 meter VHF ham receiver.
• Ensure that the circuit draws around 2.5mA from the 5V supply.

Adjustments:

• If necessary, fine tune the circuit based on performance requirements.

Note:

Remember to follow safety precautions when working with electronic components and soldering equipment.

If you are not familiar with electronics it is advisable to seek assistance from someone with experience or consult additional resources for guidance.

Conclusion:

Building and installing an FM Radio Receiver Antenna Booster Circuit can be a cost effective way to improve the performance of an FM radio receiver especially in situations where, a stronger signal is needed for clear and interference free reception.

References:

Datasheet BF324