The **E-1121-R** is a specific model of an **Active GPS Antenna**, typically used in telecommunications, marine navigation, and timing synchronization systems. It is designed to receive L1 band signals from GPS satellites. ### Technical Specifications Overview Below are the primary electronic characteristics of the E-1121-R: | Feature | Specification | | :--- | :--- | | **Frequency Range** | 1575.42 MHz ± 1.023 MHz (GPS L1) | | **Antenna Gain** | ~5 dBic (at Zenith) | | **LNA Gain** | 26 dB to 38 dB (model dependent) | | **Noise Figure** | < 1.5 dB | | **Supply Voltage** | 3.0V to 5.0V DC | | **Current Consumption** | 15mA - 25mA | | **Output Impedance** | 50 Ohms | | **Connector Type** | Usually TNC or N-Type (Female) | --- ### Core Electronic Components The E-1121-R consists of several integrated electronic subsystems: #### 1. The Patch Element The "heart" of the antenna is a ceramic patch radiator. It is specifically tuned to the GPS L1 frequency. It is designed for **Right-Hand Circular Polarization (RHCP)** to match the signals transmitted by GPS satellites, which helps minimize multi-path interference. #### 2. Low Noise Amplifier (LNA) Because GPS signals are extremely weak by the time they reach Earth (approx. -130 dBm), the E-1121-R includes a built-in LNA. - **Purpose:** It boosts the signal immediately at the source before it travels down a long coaxial cable. - **Filtering:** It often incorporates a SAW (Surface Acoustic Wave) filter to reject out-of-band interference from cellular or radio signals. #### 3. DC Bias Circuitry The antenna does not require a separate power cable. Instead, it uses **Phantom Powering**: - The DC voltage (3V-5V) is sent from the GPS receiver up the center conductor of the coaxial cable. - Internal circuitry separates this DC power from the RF signal to power the LNA. --- ### Comparison: Passive vs. Active Antennas The E-1121-R is an **Active** antenna. Here is how it compares to a passive alternative: | Feature | Passive Antenna | Active Antenna (E-1121-R) | | :--- | :--- | :--- | | **Amplification** | None | Integrated LNA | | **Power Req.** | No power needed | Requires 3-5V DC | | **Cable Length** | Limited (High signal loss) | Supports long cable runs | | **Sensitivity** | Lower | Much Higher |