How many meters can be transmitted？

[ROSELJR]

How many meters can be transmitted by PoE network cable power supply

Copper-clad iron or copper-clad steel network cable with 0.5 core copper, how many meters can be passed respectively

I want to add a hub or switch with a copper-clad iron network cable 50 meters away from one end. The PoE is a 48v power supply. The output is for a 9v hub. The power is about 7W. Can it work stably?

[AzeoTech]

You'd have to check the power supply specs, but the absolute limit is going to be determined by ohms law: V = IR.  You can calculate (or measure) the resistance of 50 meters of your cable, then plug in your desired amperage, which at 48V, 7W would be 0.145 amps (note we want the amps on the wire which is 48V, not the 9V of your hub).  Multiply the two and you'll get the voltage drop across the wire.  Subtract that from 48V and that's the voltage you'll see at the other end.  You'll also have to watch for heating and the spec on the network cable should tell you the maximum amps supported.  Those are standard, non-signal carrying calculations.  There may be other factors that will further limit it.  We use Unifi access points and those are 7W with 19W passthrough and we don't have any issues. 

Note that you aren't going to be able to plug a 9V hub/switch directly into a 48V PoE line.  I would look instead for a PoE powered switch.  I have a little Ubiquiti PoE powered switch on my desk.  It even has pass through for my phone, but of course does not provide PoE on its own since it doesn't have to be plugged into the wall.