Beacon-transmitter

Description: This transmitter is suitable for transmitter hunts, remote key finding, or radio telemetry in model rockets. It can be tuned to the two-meter band or other VHF bands by adjusting capacitor C1 and inductor L1. L1 consists of four turns of #20 enameled wire wound in the air, with a diameter of 0.25 inches (using a drill bit) and a length of 0.2 inches, center-tapped. The antenna can be made from 18 inches of any type of wire. Integrated Circuit IC2 operates as an audio oscillator, which is activated and deactivated by IC1 approximately once per second. The transmitter has a range of several hundred yards.

This transmitter circuit is designed to operate effectively within the VHF spectrum, specifically tuned to the two-meter band, which is commonly utilized for amateur radio communications. The tuning of the circuit is accomplished through the careful selection of the components C1 and L1, where C1 is a variable capacitor that allows for fine-tuning of the frequency output, and L1 is a coil with specific inductance determined by its physical parameters.

The inductor L1 is constructed using four turns of #20 enameled wire, which is wound air-core around a cylindrical object, such as a drill bit, to achieve the desired diameter and length. The center tap on L1 allows for a balanced output, which can improve the performance of the transmitter by ensuring that the signal is correctly fed into the oscillator circuit.

The audio oscillator functionality is provided by IC2, which generates a continuous square wave signal. The frequency of this oscillator can be adjusted based on the values of the surrounding components, thus allowing for modulation of the transmitted signal. IC1 serves as a control unit that periodically turns IC2 on and off, creating an intermittent transmission that can be useful for applications such as locating lost items or telemetry data transmission. This on-off cycling occurs at approximately one-second intervals, providing a clear signal that can be easily detected by receivers within range.

The design allows for a simple antenna connection, where an 18-inch wire can be used to transmit the signal. This length is optimal for achieving effective radiation of the VHF signal, ensuring that the transmitter can operate over several hundred yards, making it suitable for various practical applications, including model rocketry and search and rescue operations. Proper assembly and tuning of this circuit will yield a reliable transmitter capable of fulfilling its intended functions.This transmitter can be used for transmitter hunts, for remote key finding, or for radio telemetry in model rockets. It can be tuned to the two meter band or other VHF bands by charging Cl and Ll. 11 is four turns of #20 enameled wire airwound, 0.25 inch in diameter (use a drill bit), 0.2 inch long, centertapped.

The antenna can be 18 inches of any type of wire. IC2 functions as an audio oscillator that is turned on and off by IC1 about once per second. The range of the transmitter is several hundred yards.