Understanding Active vs. Passive GPS Antennas
Before diving into power requirements, it’s important to distinguish between active and passive GPS antennas. A passive antenna has no built-in amplifier and relies solely on the GPS receiver’s sensitivity. In contrast, an active GPS antenna includes a Low-Noise Amplifier (LNA) to boost weak signals, making it ideal for applications where signal strength is critical, such as in vehicles, marine navigation, or remote tracking devices.
Power Requirements for Active GPS Antennas
Most active GPS antennas operate on 3.3V or 5V DC power, though some may require up to 12V. The exact voltage depends on the antenna’s specifications, so always check the manufacturer’s datasheet. Supplying incorrect voltage can damage the amplifier or degrade performance. The power is typically delivered through the same coaxial cable that carries the GPS signal, a method known as DC power over coax.
Wiring and Connection Setup
To power an active GPS antenna, you’ll need a compatible GPS receiver or an external power injector. Many GPS receivers have a built-in bias tee circuit, which supplies power through the antenna port. If your receiver doesn’t support this, you’ll need a separate power injector that connects between the antenna and the receiver.
- Check the receiver’s specs – Ensure it provides the correct voltage.
- Use high-quality coaxial cables – Poor cables can cause power loss or signal interference.
- Avoid voltage drops – Long cable runs may require higher voltage or an in-line amplifier.
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Common Power Supply Methods
There are two primary ways to power an active GPS antenna:
- Directly from the GPS receiver – Most modern receivers include a bias tee to supply power via the antenna port.
- Using an external power injector – If the receiver lacks power output, an injector can be added to the setup.
- Some antennas also support USB power, which is useful for portable or PC-based GPS applications.
Troubleshooting Power Issues
If your active GPS antenna isn’t working, power-related issues are a common culprit. Here’s how to diagnose them:
- No signal? Verify that the antenna is receiving the correct voltage with a multimeter.
- Weak signal? Check for cable damage or excessive length, which can cause power loss.
- Overheating? Excessive voltage can damage the LNA—always match the antenna’s rated input.
Best Practices for Reliable Performance
To ensure long-term reliability:
- Use shielded cables to minimize interference.
- Keep cable runs as short as possible.
- Secure all connections to prevent power interruptions.
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This article does not suggest the current draw of typical antennas.
I had the idea of fitting an LED and resistor to an SMA plug to check for DC supply, but can typical receivers source e.g. 5 mA?
That’s correct — most antennas themselves don’t draw current unless they’re active antennas with a built-in LNA. Typical receivers that supply DC over the coax (for active GPS, DVB-T, etc.) usually provide a few volts at a few tens of milliamps. Many GPS modules, for instance, can source around 20–50 mA for an active antenna.
If you just want to check for DC bias, an LED + resistor on an SMA plug would work, but keep the current draw low (e.g., <2 mA) so you don’t risk overloading the receiver’s bias circuit. Alternatively, a multimeter is safer and gives you the exact voltage present.