Affordable PowerLink SP402F 4+2-port PoE switch

I decided to buy an inexpensive switch for home use—or, more specifically, for setting up various PoE Ethernet devices—and while I was at it, I wanted to see what an inexpensive PoE switch from PowerLink was like.


I’d already published a very detailed comparison and explanation of what PoE is, but I had to sell that switch. Since I still need to get work done, I bought a simpler model, and a noticeably cheaper one at that.

Why this particular brand? Simply because when I was looking at what was available, I came across PowerLink switches. As it turned out, they cost about the same here as on AliExpress, if not less, and shipping was free—and, of course, much faster than from AliExpress.

When I placed the order, for some reason I thought the model had an external power supply. I could be mistaken, but I think there was only one photo at the time, showing the front panel.
In any case, it arrived quickly. Everything was packed in a fairly large box, which contained the switch itself, a power cable, and a manual. The box lists the basic specs, and in this case I was especially interested in the PoE power budget. It’s rated at 65 W, or 16.25 W per port.


For anyone interested, I filmed an unboxing and got a bonus toward my next purchase for it (Rozetka has a nice little savings program).


The manual lists all the available models, from the entry-level 4+1 with 100 Mbps ports to the “top-of-the-line” 8+2 with gigabit ports. I’d like to try that one too, and will most likely use it to replace the switch I currently use as my main home switch. There’s also an alternative in the latter case: a 4+1 with gigabit ports plus 1 SFP port.


The case is fairly large: 200x120x45 mm.


All the ports, indicators, and controls are on the front panel; the only thing on the back is the power socket.


On the left are the operating mode switch, four PoE ports, and a pair of ports for connecting switches to the same network. Two ports are handy when switches are installed along the same backbone: connect the recorder to one port and the next switch to the other.
Some people will say this is the wrong way to connect them. That’s partly true, but when the links are very long—for example, in a video surveillance system—the distances can be 200–300–400 m, and the standard 100 m just isn’t enough. So you have to split the distance between links.


There are ventilation slots on the sides and a power socket on the back. By the way, the built-in power supply is both an advantage and a drawback. For example, when I install switches on site, I replace the stock power supply with a better-quality Mean Well, usually an LRS series model rated for 48 V (I have one sitting here, waiting for a review). They’re more reliable. That’s not an option here, but if you’re using the switch simply “at home,” the built-in supply should be perfectly adequate—and it’s an advantage in that nothing is dangling next to the switch.
There are no feet on the bottom, but there are holes for wall mounting. There are also holes on the sides for mounting “ears” to install it in a 10-inch rack, but they’re not included. Too bad.


But I was much more interested in looking inside and checking what kind of PoE it uses.


I’d even say there’s plenty of room inside, which should help with cooling. The case is also metal, which should help keep temperatures down as well.


The power supply is a budget model. There’s no input filter or varistor, but they did fit a 68 µF capacitor, which is perfectly adequate for operation on our mains voltage. They didn’t forget the thermistor, either.
The interwinding capacitor is the correct Y type, and there’s an output filter to reduce ripple. The output capacitors have a total capacitance of 2x330 µF.


The board is held in place by three screws and gets its power through a connector, so it’s very easy to remove.
You can see the quad PoE port transformer and the dual UpLink transformer.


There aren’t many components on the underside. The board is clean, and the soldering is neat.


There’s no input fuse; it’s been replaced with a jumper. On the plus side, they fitted an SMBJ58CA TVS diode (58 V) in parallel with the power supply.
The auxiliary voltage converter is built around an XL7005, which is a pretty clear indication that this device was developed in China.


Ethernet switching is handled by the IP178G, an eight-port switch chip made by icplus.


But it was much more interesting to take a look at the PoE power subsystem. It is handled by a large unmarked chip and four DTM6940s. I couldn't find a datasheet, but judging by the circuit, I'd guess they're MOSFETs. Nearby are current-sense resistors and overload/short-circuit protection circuits.


Four SMAJ58A TVS diodes are installed underneath the PoE power section, protecting each port against voltages above 58 V.


Now let's see how PoE works.
1. The power supply outputs about 51 V, which is perfectly normal and will give it a slightly longer reach than the usual 48 V.
2. Power is supplied to the devices over the signal pairs, so if needed, you can even connect and power two cameras using a single four-pair cable.
3, 4. This is the most interesting part. Budget devices like this often use so-called Passive PoE, where power is always present on the port. This one works properly: with no device connected, the port has 11–12 V, and full voltage is applied only after negotiation with the load. Short-circuit current in this mode is just 160 µA, so you can safely crimp, short, or cut a cable connected to the switch.


And now for a few tests.
I've already explained that surveillance switches often include an Extend function. Its main feature is that it forcibly switches ports to 10 Mbps, allowing them to work with surveillance cameras (and other devices) over links longer than 100 m. Typically, we're talking about 200–300 m, though I personally wouldn't go beyond 200 m.

There are three switch positions here: VLAN, OFF, and Extend. I don't need the first mode for now; the second is normal operation, and the third limits the speed to 10 Mbps.



I tested it in two modes, normal and Extend, with traffic going from the PoE ports to the UpLink port. In normal mode, the speed was 75–80 Mbps; in Extend mode, it was 9–9.5 Mbps.
I didn't test the speed in the opposite direction, since that wasn't particularly relevant for this kind of use.


With Extend enabled, the UpLink ports retain their full speed, which in this case was also 75–80 Mbps.
I think the reason for the 4+2 port configuration is that Extend mode can only be controlled for a number of ports divisible by four. So we have an eight-port chip, but can switch only four ports. Otherwise, the configuration would have been 6+2.


In VLAN mode, all ports run at full speed.


Of course, I also tested the switch with a real surveillance camera. In this case, it was an 8 MP Hikvision camera, and there were no problems.


Conclusion.
An ordinary budget switch, but with properly implemented PoE, port protection, and an Extend function. It's suitable for setting up a surveillance system with up to four cameras. You can connect more, but then you'll need either a switch with more ports or a second one like this.
The only relatively significant drawback is that the power supply has no input filter or varistor. Otherwise, the switch delivers 100% of what you'd expect for the price.

That's all. I hope you found this useful. I've seen similar switches on AliExpress, but without testing them, it's hard to say how well they're implemented.