The answers to this question clearly state that low voltage and high voltage cables should be kept separate; does this apply to low voltage (9v) power cables and CAT5?

The problem: I would like to extend Wi-Fi coverage in my house by using a range extender, the unit is powered by a low voltage (9v) adapter rated at 0.6A. I would like to run the cable for this unit in parallel to the CAT5 cable over a distance of approx 15m, surface mounted in PVC trunking. Will this cause any problems?

3 Answers 3


You can run a cable next to your CAT cable. You just cant really use the twisted pairs inside the cat cable, unless you are using PoE devices, which deal with the interfierence.

The problem is that the twisted pairs cause an electromagnetic field in the cable which is NOT part of the cable causing issues. Running low voltage, even high voltage with a SEPERATE cable next to it never caused me any issues. I even saw them cable tied to each other.

The problem only starts when you running Ethernet cable next to full phase cables, ie power to your house, or 2,3 phase cables for big machines. The electrical feedback caused by heavy machinery causes changes in the electromagnetic field on these cables, which affect Ethernet, WiFi, etc, and that is when it is strongly advised to run these cables far away from these power cables.

Your puny 0.6A modem wont cause any of this because it doesn't use mechanical engines which generate feedback, just simple linear voltage regulators and filters which help reduce this problem.

100 megabit or gigabit, always ran full speed.

  • 'puny 0.6A modem...' I feel a complex coming on...
    – 7caifyi
    Jan 16, 2016 at 18:06
  • 1
    It had crossed my mind to use some of the unused strands in the CAT5; but that's definitely ruled out now.
    – 7caifyi
    Jan 16, 2016 at 18:09
  • Yea, dont use the "unused" strands, its logical thinking but will create massive problems. No complex :) Just ~9watts is puny energy comapared to 5000watts, which will cause issues.
    – Piotr Kula
    Jan 16, 2016 at 18:12

There's a decent probability that this won't work due to voltage drop from the power adapter, and not through interference: Voltage Drop Calculator

A 15m run using 22AWG wires yields a voltage of 8 at the range extender. This may or may not be sufficient to power the extender.

Power over Ethernet devices typically use 48v to minimize the voltage drop.

Alternatively, you could use a wifi access point with a powerline ethernet adapter; I've used this setup with great success.

  • 1
    Yeah, a PoE link would be a better bet here than trying to run 9V over 15m of 22AWG. Jan 17, 2016 at 16:26
  • Why would you use 22AWG? 12 and 14 AWG are perfectly cheap. Jan 19, 2016 at 4:12
  • I always forget about the voltage drop; I managed to source a closer power supply, and used 14AWG. I've marked @ppumkin's answer correct as this answered the question, but +1 for a very relevant answer, thank you.
    – 7caifyi
    Jul 2, 2016 at 14:01

That won't cause any problems, but I would consider a PoE Wireless Access Point rather than a range extender. All range extenders cut your throughput in half and significantly increase latency.

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