# How to Build a Repeater for Beginners
A repeater is a device that receives and retransmits a radio signal, extending its range and improving its quality. Repeaters are useful for communication in areas where the terrain or distance may interfere with the direct transmission. In this article, we will discuss how to build a basic repeater system for the General Mobile Radio Service (GMRS), a licensed radio service in the United States that operates in the VHF and UHF bands. GMRS is available to individuals for personal or business use, and allows communication between handheld, mobile, and base station radios.
## Components of a Repeater System
A basic repeater system consists of the following components:
- Antenna: This is the device that receives and transmits the radio signals. A repeater usually uses a dual-use or omni-directional antenna, which can cover a wide area in all directions. The antenna should be mounted as high as possible, such as on a tower, a building, or a hilltop, to maximize its coverage.
- Feedline or Hardline: This is the cable that connects the antenna to the duplexer. The feedline should be as short and thick as possible, to minimize the loss of signal strength. A hardline is a type of feedline that has a rigid metal casing, which provides better protection and performance.
- Duplexer: This is a device that allows the repeater to use the same antenna for both receiving and transmitting, without interfering with each other. A duplexer filters and isolates the incoming and outgoing signals, and directs them to the appropriate ports. A duplexer should be tuned to match the frequency and bandwidth of the repeater.
- Receiver: This is the device that picks up the incoming signal from the antenna, amplifies it, and converts it to an audio signal. The receiver should have a good sensitivity and selectivity, to be able to detect weak and distant signals, and reject unwanted signals from other sources. The receiver should also have a squelch circuit, which mutes the audio output when there is no signal or only noise.
- Repeater: This is the device that controls the operation of the repeater system. The repeater takes the audio signal from the receiver, modifies it if needed, and sends it to the transmitter. The repeater may also add a tone or a call sign to identify itself, and perform other functions such as time-out, hang-time, and courtesy beep. The repeater should have a stable and accurate frequency, to avoid drifting or interfering with other repeaters.
- Transmitter: This is the device that converts the audio signal from the repeater to a radio signal, amplifies it, and sends it to the antenna. The transmitter should have a sufficient power output, to cover the desired area and overcome any interference. The transmitter should also have a good modulation and deviation, to ensure a clear and intelligible transmission.
## Steps to Build a Repeater System
To build a repeater system, you will need to follow these steps:
1. Prepare design drawings: First, you need to determine the model and specifications of the repeater system that you will be using. You will need to choose the frequency, bandwidth, power output, and other parameters of the repeater, as well as the type and size of the antenna, feedline, and duplexer. You will also need to consider the location, height, and orientation of the antenna, and the layout and wiring of the other components. You can use online tools or software to help you design and simulate your repeater system.
2. Arrange and install according to the drawings: Next, you need to acquire and assemble all the necessary components for your repeater system. You will need to connect the antenna to the feedline, the feedline to the duplexer, the duplexer to the receiver and transmitter, and the receiver and transmitter to the repeater. You will also need to provide a power supply and a grounding system for your repeater system. You should follow the manufacturer's instructions and safety precautions when installing and connecting the components.
3. Test and use: Finally, you need to test and adjust your repeater system, to ensure that it is working properly and efficiently. You will need to tune the duplexer to match the frequency and bandwidth of your repeater, and check the SWR (standing wave ratio) of your antenna system, to measure the impedance and efficiency. You will also need to check the sensitivity and selectivity of your receiver, and the power output and modulation of your transmitter. You can use a radio, a SWR meter, a wattmeter, a frequency counter, and other tools to test and monitor your repeater system.
Once your repeater system is ready, you can start using it for communication. You will need to obtain a GMRS license from the FCC, and follow the rules and regulations of the service. You will also need to identify your repeater by transmitting its call sign at the end of each transmission or every 15 minutes. You can also set up a PL (private line) tone or a DCS (digital code squelch) code to access your repeater, and prevent unauthorized users from using it.
Building a repeater system for GMRS is not a difficult task, but it requires some planning, preparation, and testing. A repeater system can enhance your communication range and quality, and allow you to communicate with other GMRS users in your area. By following the steps and guidelines in this article, you can build your own repeater system for beginners, and enjoy the benefits of GMRS.