Before you buy that RJ45 coupler, consider a $15 network switch or a single longer cable. Either one will usually serve you better. The coupler itself works fine, but it adds another spot where a network fault can hide.
The appeal is obvious. You shift your desk a few feet and the Ethernet cable that used to reach your computer no longer makes it. A spare cable is sitting in a drawer, and a small coupler can join the two in seconds.
It needs no outlet, no setup guide and no networking certification. A well-made coupler also shouldn’t slow your internet connection in any way you’d notice.
What a coupler does (and doesn’t do)
Network hardware doesn’t get much simpler than an Ethernet coupler. It’s two RJ45 sockets wired to each other. There’s no signal boost and no separate Ethernet link. The cables on either side act as one continuous run.
One coupler with good connectors will do the job without complaint. The catch is that the extra connection can fail, and the odds go up if the adapter is cheap or sits where it keeps getting knocked.
A poor join tends to show up as occasional dropouts, transmission errors, or a link that drops to 100 Mbps when it should run at 1 Gbps. If any of that happens, try a good-quality cable with no coupler first. That’s quicker than spending an afternoon rebooting your router and phoning your internet provider.
The 328-foot rule doesn’t care about your adapter
Length sets the other limit. Standard copper Ethernet maxes out at 328 feet (100 meters) per channel, patch cords included. Two 200-foot cables joined together put you past that limit, and a coupler doesn’t reset the count.
Cable maker trueCABLE ran tests on various combinations of Cat6 and Cat6A cables and couplers using a Fluke DSX-8000 cable tester. Runs with three couplers mostly passed, although one scraped a marginal pass, which technically counts as a failure. Runs with four couplers failed.
Since those numbers came from particular cables and particular couplers, four isn’t a hard limit for every setup. They still show why adding more joins than necessary is a bad idea.
For one PC or console, buy the longer cable
When you’re hooking up a single computer or console, begin with one Ethernet cable that’s long enough to reach. You lose the extra connection, and there’s no extra hardware that needs an outlet.
Give it some slack as you route it around furniture, since a cable stretched tight behind a desk invites problems. Decent Cat5e or Cat6 cable will normally carry a Gigabit connection, and paying for Cat8 won’t make up for careless routing.
When a switch makes more sense
Things look different if the cable is already run. Maybe you spent half an afternoon getting Ethernet to your entertainment center, and now a TV, a console and a streaming box each need a port. This is the job for a small unmanaged network switch.
The incoming cable goes into one port and your devices fill the others. On a five-port model, one port handles the link back to the router, leaving four free.
A switch creates separate Ethernet links, which a coupler can’t do, so each link gets its own distance limit. Basic unmanaged five-port Gigabit switches cost around $15 and work without any configuration.
Switches have downsides. They need power, and a 1 Gbps model will limit transfer speeds on cables rated for faster standards.
If you’re wiring up a security camera or a wireless access point, check one more detail. A standard non-PoE switch doesn’t deliver Power over Ethernet to connected devices, so anything that relies on it needs a PoE-capable switch or an injector.