I want to connect two Ethernet (UTP) cables. Both of them have connectors only on one side. Is it okay to solder the wires together?

  • Could it affect maximum speed? (For example I wouldn't be able to use gigabit ethernet.)

  • Could transferred data be significantly corrupted?

  • What about electromagnetic interference?

The cable would be approxametly 4 m long.

  • \$\begingroup\$ How long would be the resulting cable? The point where the joint is done creates a discontinuity in the twisted pairs so there will be some signal degradation, but most likely it will work. \$\endgroup\$
    – Justme
    Aug 20, 2019 at 15:36
  • 2
    \$\begingroup\$ do not solder the wires ... the resulting connection is brittle ... twist wires together and cover with heatshrink tubing \$\endgroup\$
    – jsotola
    Aug 21, 2019 at 5:49
  • \$\begingroup\$ @jsotola, that sounds good (and easier) but I want to glue it in some box to protect the connection so that is no problem. \$\endgroup\$
    – jiwopene
    Aug 21, 2019 at 14:01

3 Answers 3


As Justme mentioned in the comments, there will be a slight disturbance from the joint. Enough to measure if you have the right tools, not enough to be a real problem if you take a little care.

The main problem is not the solder joints themselves,but rather that you have to untwist the wires in the area of the joint.

Unravel the wires as little as possible (a couple of centimeters of untwisted wire should be fine.)

Solder neatly, and use heat shrink tubing to insulate the soldered joints.

Soldered joints are mechanically weak. Do not rely on them to hold if your cable will be moved around a lot. In that case, you should see about taping or heat shrinking a reenforcment to the outside of the cable.

I wouldn't do that at work - I'd just get a longer cable bought or made.

At home, on the weekend, for something temporary or for something longer lasting but which won't be moved or wiggled I'd probably do it and not worry about it.

Whatever you do, don't exceed the maximum segment length for ethernet. There's a maximum length that counts from active device to active device. It includes all cables - in the walls, the server rack, and to the end devices.

If you exceed that length with your extra long cable, you can expect problems.

  • \$\begingroup\$ It looks fine. I want to do it only at home. \$\endgroup\$
    – jiwopene
    Aug 20, 2019 at 16:50
  • 3
    \$\begingroup\$ @jiwopene I'd also add: stagger the joints. If within each pair you solder maybe 2cm apart and make sure to carry on the twisting of the pair between, there will be slightly more physical strength as the wires are twisted around each other. \$\endgroup\$ Aug 20, 2019 at 17:49
  • \$\begingroup\$ I have done this plenty of times in the lab with no problems. \$\endgroup\$
    – user4574
    Aug 5, 2020 at 20:37

Solder joints will affect the impedance of the cable by adding a bit extra of inductance and maybe more capacitance between the cables. This probably won't change the speed but don't be surprised if the port negotiates to 100Mbps.

Also, make sure that the solder joints get adequate strain relief by using heatshrink or some other means of isolating the solder joint from mechanical movement. Any kind of force directly on the solder joint could crack the solder or break the wire.

The best thing might be to get a tool less Ethernet coupler.

enter image description here

Source: https://www.netsys-direct.com/products/gf-innovations-tool-less-10-100-1000-ethernet-coupler-splicer-gf2120?utm_medium=cpc&utm_source=googleshopping&variant=33878314511&_vsrefdom=adwords&gclid=EAIaIQobChMIrsOGufyR5AIVkq_sCh1WoQ_GEAkYBiABEgKHAfD_BwE


I'm always a little puzzled by the number of people that consider soldering an inferior connection. Yes, I totally agree different connections/solder/patching on a wire will mess up induction/capacitance/etc, as Voltage Spike has pointed out, and it's certainly an unusual and less than ideal method for network cabling. But "mechanically weak" is stretching it a bit. If you rely on flux cored solder, and are trying to use barely-enough temperatures, yes your connections will be poor. If you use soldering acid in the good old black bottle like I have for decades? After thousands of soldered joints in all sorts of environments, I don't believe I've ever had a failure of a soldered connection. I simply go by the experience I've had myself with all sorts of connection types.


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