The core logic behind explaining the transmission distance of PoE power supply can be summed up in just four words: "path loss" and "signal-to-noise ratio".

1. The "value" of network cables (material is king)

This is the number one killer affecting distance.

Pure oxygen-free copper wire: Just like a thick and smooth high-grade water pipe, it has extremely low resistance and runs steadily for 100 meters.

Copper-clad aluminum/copper-clad iron wire: This type of wire has a copper plating on the outside, while the core is made of aluminum or iron. Aluminum has a much higher resistance than copper, so the electricity dissipates as heat very quickly.

To put it simply: a poor-quality network cable is like a rusty water pipe; the water leaks out before it even reaches the end of the road.

2. The thickness of the wire core (AWG value)

The specifications for network cables include an AWG parameter (such as 23AWG or 24AWG).

The smaller the number, the thicker the wire core.

23AWG wire is thicker than 24AWG wire. The thicker the wire, the lower the resistance, the stronger its ability to carry large currents, and the longer the transmission distance.

3. The "body temperature" of the environment (the higher the temperature, the greater the resistance).

This is a basic physics principle: the higher the temperature, the greater the electrical resistance of the metal.

If you run network cables in outdoor conduits exposed to direct sunlight, or close to high-power equipment that generates a lot of heat, power consumption will increase significantly.

Overly tight bundling: Dozens of PoE network cables are tightly bundled together, preventing the heat generated during operation from dissipating and artificially shortening the transmission distance.

4. Data is more "delicate" than electricity (signal attenuation).

Many people have a misconception: as long as the device's light is on, there is no problem with the power supply.

But in reality, electricity often travels farther than signals.

PoE transmits "power + data". When the network cable is too long, the power may not be cut off, but the data signal (high-frequency pulse) has become "noise" due to interference and attenuation, causing the device to have power but no picture or data.

5. The switch's "black technology" (long-distance mode)

Why do some industrial switches dare to be labeled as 250 meters?

They adopted a strategy of "sacrificing speed for distance": forcibly reducing the network speed from 1000M/100M to 10M.

When the speed is reduced, the signal's anti-interference ability becomes stronger. Just like in order to make water flow further, we reduce the water pressure and slow down the flow rate, and the water can flow more steadily.