I have a VDSL home network that consists of a tp-link modem-router (Archer VR400), connected to a splitter (filter) by a 1 meter RJ11 cable.

My current speed by Ethernet connection is 90-95/100 Mbps, so it seems my infrastructure is pretty reliable.

My question is: will extending the length of the RJ11 to a 10m cable may greatly or noticeably decrease my internet connection?

Also: are there any types and quality standards for RJ11 cables, such as Ethernet cat 5, cat 6 and etc ?

I stumbled upon this very old question, but could not find a clear answer for my question: How important for speed is the length of the phone cable between the wall and the modem?

Any suggestions?

  • The standard recommendation from the telco/ISP is to use UTP (e.g. Cat3 or better) cable with RJ-11 plugs to connect the xDSL modem to the wall plate. Avoid using "phone extension cable" (i.e. straight, not-twisted wire).
    – sawdust
    Aug 9, 2020 at 22:21

5 Answers 5


Telephone cable for RJ11 connections is simple round cable with some twist to the wires (but not in pairs). You can extend by 10 meters without any significant degradation. The signal from the ISP is meant to travel over that kind of cable. Use good quality (Belden or like) cable. Cheap cable may be inferior construction.

No one can know precisely your situation (which is why you won't get a 100% black or white answer).

So add your cable and relocate your gear.

  • 1
    Telephone cable is usually straight, not twisted.
    – Moshe Katz
    Jun 7, 2020 at 14:10
  • Yes. Certainly not twisted like Ethernet. I clarified my post.
    – John
    Jun 7, 2020 at 14:15
  • 2
    @john, don't listen to the peanut gallery. Rj-11 is the registered jack, not the cable. And vdsl that's over 10Mbps shouldn't be on straight pair cat-3. It should be installed over cat-5/5e twisted pair to ensure the speeds the customer is paying for. Jun 7, 2020 at 18:18
  • 1
    This was usually ok for ADSL etc. I don't think it's the case for the newer technologies, you will find in installation manuals and even on Wikipedia the local loops back to the dslam are unshielded twisted pair. It makes sense, everyone had to upgrade buildings/schools from cat-3 10base-t to cat-5 to support 100Mbps Ethernet. The same problems apply for DSL after 10Mbps, cross talk, emi pickup, etc. Jun 7, 2020 at 18:44
  • 1
    @pizza higher jitter or ping is u likely unless you are saturating the connection. DSL carves out frequencies it can use, and it may just carve out fewer, so slightly less bandwidth but virtually no jitter/ping unless the connection needs to buffer more.
    – davidgo
    Jun 7, 2020 at 19:41

The best thing you can do is home run a CAT-5E solid conductor cable back to the DMARC. (Outside box where the PSTN copper line comes in.) You can put one DSL filter here in parallel with the CAT-5E for the rest of the RJ-11 voice outlets instead of putting one on each phone outlet.

Why you don't want to use old house wiring or wiring blocks:

Straight pair, cheap voice cables (usually found installed in pre-1990's buildings) suffered from noise, emi pickup, and crosstalk issues.

The old wiring blocks don't even meet cat-3 specifications. (Screw and terminal) they were replaced with the 66-block style that do meet the requirements, you can find mini versions at Lowe's or home depot etc.

  • CAT-3: Should be used for 10Mbps or less.
  • CAT5: Should be used up to 100Mbps.
  • CAT-5E: Should be used for 100Mbps ~ 1000Mbps. (If you are lucky enough to be offered these speeds by the provider)

"are there any types and quality standards for RJ11 cables, such as Ethernet cat 5, cat 6 and?"

~Yes, working at a local CLEC here in PA, CAT-5E was mandatory for new installations. This was a recommendation from Verizon, because we were using their network equipment etc. (They told us mismatching awg/category types could cause signal reflection in the inside wiring.)

To be honest, it doesn't even make sense to use the other cables categories, at this point cat-5E is cheap enough that it should be installed if you are anticipating higher speeds in the future offered by the ISP, or if you just want to ensure the best possible SNR ratio from DMARC to modem.

Sometimes this isn't an option, for instance if you are renting an apartment. The best thing to do in that scenario is to see if the landlord would let you hire someone to run the cable for you.

If all else fails, you could try the extension. But if you don't pop open a RJ-11 outlet and take a peek at the wiring to see what type it is, you could actually degrade the signal with an impedance mis-match, I.e, the AWG sizes are different...

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  • Unfortunately, there is not much I can do with my infrastructure. Yes this is an apartment building built in the 80s, so cat 5 or overall any in-wall wiring will not meet modern standards. I do however know that the wiring from the DMARC to the PSTN is actually maintained very well and meets high quality standards (well, at least up to 100 Mbps, where I am currently provided with 90-95 Mbps, and jitter of 1, and a very good SNR).
    – Pizza
    Jun 8, 2020 at 4:46
  • Also, although it is not something I could implement, I'd like to thanks this very informative well thought answer. That is some very nice general knowledge to have.
    – Pizza
    Jun 8, 2020 at 4:51
  • Another question regarding splitters: I am currently using the splitter just to convert an "american" jack" to a "european plug", with no need of a telephone line. Would you recommend removing it? I was told splitters usually also deal some noise problems, and better use them even if not needed for additional telephone line compability.
    – Pizza
    Jun 8, 2020 at 8:20
  • Not knowing how those outlets are wired I would keep it. They do reject band noise in the form of a LCR band pass filter. (Inductor, capacitor, resistor, that Cuts off anything outside of the DSL frequencies.) In your case, write down the signal to noise ratios from the DSL modem webgui before and after trying the extension. This answer was more for if you run into trouble extending it, you know you have some sort of cabling mismatch.(and know how to fix it) You are welcome. Jun 8, 2020 at 14:31

It could matter if you are already right at the distance limit for DSL. There's only so far that a DSL signal can travel from the phone company "Central Office" (or any signal amplifier they may have) and if you are outside the range it will start dropping a lot of packets due to signaling errors.

That said, it's not such a big deal to just try it. Your DSL modem should have a web page where it shows error statistics, so you can compare it before the change and after the change. If it turns out that it's too far, just go back to the shorter cable and figure out a different place to put the modem.

Other than that, you should not have any problems.

  • 1
    This answer is non-sense. Vdsl is signal repeated by the PSTN on the street level pair controllers. It's the ISP's responsibility to make sure the customer has proper SNR margins at the dmarc. -1 for the false comment under John's answer, and for your answer based on fallacy. Jun 7, 2020 at 18:25
  • 2
    @Tim_Stewart - sorry to disagree with your down vote, I think this answer is substantially correct. It could be clearer that there is still bandwidth loss dependant on distance. Also, I've not heard of VDSL being repeated by pstn (at least in New Zealand or Aussie)- rather it is sent to cabinet - usually by fibre, and VDSL is then generated in the cabinet - no repeating. Also, in NZ and AU, VDSL is delivered over the same old - cat 3 I assume - definitely not cat5) pairs ADSL used. Even jumpering in new buildings do this.
    – davidgo
    Jun 7, 2020 at 19:46
  • @davidgo, odd they have been around for quite some time here. We could have the physical pairs switched through these devices all the way back to the headend if a pair came up damaged in a test. en.m.wikipedia.org/wiki/ADSL_loop_extender Jun 7, 2020 at 19:55
  • 2
    @tim_Stewart - I'd never heard of that before today. In NZ, to the best of my knowledge, you either got ADSL because you we're close to an exchange/cabinet or not - repeaters were not something ever mentioned. If you were to far from exchange - bad luck - you suffered with dialup or used satellite (or more recently 4g cellular provided off a government/cell provider shared initiative called RBI- rural broadband initiative - in NZ). My experience in Aussie is much more limited, but much, much worse - nothing better then ADSL/$$4g in many CBD buildings until last year!
    – davidgo
    Jun 7, 2020 at 20:04
  • (Re Aussie - unless you paid $$$$ for special fibre. Like $500/month - not OK for small business/branch offices)
    – davidgo
    Jun 7, 2020 at 20:05

I learnt alot from all the answers and comments back then when asking this question - yet in general, most of the answers and comments summed up to "it is not something anyone can guarantee for 100%", and overall it is something that I'll know only when I try.

I nearly forgot about this question, but I can say that after trying a simple 10m long RJ11 cable (kept the filter), I saw almost no negative effect on my bandwidth, nor on any ping / jitter / dsl errors statistics at all.

I do however must state again that my inhouse and overall building and street infrastructure seem to be decent, as I was and still getting 90-95/100 Mbps, and this solution might not work for everyone as answers to this question demonstrate.


Due to voltage drops you want your line to the green box as short as possible.

Put your router as close to your first socket as possible for fastest internet speeds. (Shortest cable length)

Most older /standard gear only supports 100mbs. (you'll only get 95ish... Voltage drops)

Consider your router a repeater... It takes the signal and then retransmits it at full power.

If WiFi is weak, you can get repeaters, (access points) ... But cat 5 should be good for at least 50m on the internal Lan

Cat5/6 uses four data cables (transmit +/-, receive +/-)

Telephone uses two ( +/- ) which transmits and receives (bandwidth issue )

You can use a longer cable. But it isn't recommended.

WiFi is a bottle neck

Why do you wanna move the router?

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