Self-Powered Automatic Repeater

Figure 1 

The circuit was designed to create an automatic repeater that would retransmit a received signal over the amateur radio frequency band.

• Repeater – a device that regenerates information at a higher value than it was received
• Radio Repeater – an electronic device that prevents the degradation of signals as it travels long distances by retransmitting, at an amplified level, the received low intensity radio signals
• Yaesu – a well known brand that produces high quality ham radios
• Metal Oxide Semiconductor Field Effect Transistor (MOSFET) – a device utilized for switching and amplification of signals

The operation of the circuit initiates by commencing the squelch circuit of radio 1 as it receives a radio signal. The squelch circuit cuts off or suppresses any of the functioning receivers when the signal becomes weaker than the noise. The presence of audio signal turns ON the MOSFET, even by a small amount of the signal. It will continue to function as amplifier and as switch until the audio signal sets off. During this operation, radio 2 is ready for broadcasting. As radio 2 goes on air, it regenerates the signal received from radio 1 through C1 and P1 content.

The MOSFET BS108 is designed for high voltage, high voltage display drivers and high speed switching applications such as TTL, CMOS logic, relay drivers and line drivers. In the circuit, it has low threshold voltage across the gate to supply mode. When the threshold voltage has been exceeded, the MOSFET will start to turn ON. The threshold voltage is a parameter used to identify the amount of voltage needed to initiate the conduction.

The radio 1 can be of any type of radio but radio 2 is recommended to be made of Yaesu to provide better quality of transmission using ham radio or amateur radio.

Repeaters may be utilized not only in amateur radio communication, but also in several fields including fiber optic network, where it consists of an amplifier, a photocell, and a LED or IR signal that needs amplification; in cellular telephone system where it is part of a group of transceivers in a geographic area; in wireless communications where it consists of an amplifier, a transmitter, a radio receiver, two antennas, and an isolator; in digital communication systems where it is used to receive and regenerate digital signals via electromagnetic medium; in satellite wireless systems where it is termed as a transponder that receives uplinks and retransmit them to different locations; in computer systems where the bus of two computers in a different chassis are being connected; and in network systems where it regenerate incoming optical, wireless or electrical signals.

Source:www.zen22142.zen.co.uk/Circuits/rf/rxtx.htm