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Why does answering cordless phones cause some wireless connections to drop?

When I answer my cordless phone, I get knocked off the internet on
my wireless connection. What can I do to resolve this problem?

This is a problem that many people are unaware of, but happens quite
often: household wireless phones and computer wireless (WiFi)
connections can come into conflict.

There are a couple of solutions.

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To be clear, I’m not talking about cellular or mobile phones. The issue here is caused by more traditional cordless land-line phones.

These phones typically operate on one of three frequency bands:

  • 900 megahertz

  • 2.4 gigahertz

  • 5 gigahertz

“There are two solutions: one simple, one free.”

As I understand it, the higher frequency bands typically offer longer range and improved quality over the lower.

By now you might guess where this is headed.

802.11b, the most common WiFi protocol, also uses the 2.4 gigahertz band. And 802.11a, currently less common, sits in the 5 gigahertz band.

There are two solutions: one simple, one free.

Simple: buy a new phone, making sure it’s not using the frequency range that’s used by your WiFi connections. My guess is that you’re probably using 802.11b, since it’s most common, so simply get a 900Mhz, or a 5Ghz phone and you should be set. Give your old phone to a friend who’s not using WiFi.

Free: move your WiFi equipment away from your phone. How far away depends on everything from the specific equipment and phones involved to the layout of your home or office. But if you can, for example, swap your cordless phone with a different phone further away in the house, that might be a start. Or if you can move both your access point / router and your laptop away from the cordless phone, that might also help. As you can see this approach, while cheap, will require a little bit of trial and error to see what works in your situation.

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7 comments on “Why does answering cordless phones cause some wireless connections to drop?”

  1. The best solution would be either use a regular fixed wire phone and continue using your wifi or using a LAN card type normal regular modem and using a cordless phone. In this case the above soultion is the only one that can solve the problems of disturbance and drops.

    Reply
  2. Simply change the channel your wireless router is broadcasting on (see your router settings). You generally want to be 3-4 channels above or below what your phone is on. Every channel is 5MHz apart from a neighboring channel. You generally want to be at least 13MHz apart (25MHz perferred) for optimal performance.

    Think about it like tuning your radio. If you are trying to listen to 100.3 and set it to 100.2, you may still hear 100.3, but receive interference from another network. The channels are only clear if the frequencies they are broadcasting on are far enough apart, but at one point, the signal is perfect.

    True, you generally might now know what channel your phone is on in, say in that 2.4GHz range, but you can test and see the 3 extremes. Channel 1, 6, then 11 and see which one works best for you.
    A lot of new routers, allow automatic detection of the best broadcasting channel. A lot of older ones are set to 6 by default.

    Reply
  3. 802.11b?

    You think ‘b’ is most common? Where’d you get that from?

    Isn’t 802.11g (note the ‘g’) more common?

    802.11b predates ‘g’ by some time – there are still a lot of installations running it. But you’re quite right, ‘g’ would be growing in deployment, and could have overtaken it by now.

    – Leo
    29-Oct-2008
    Reply
  4. I prefer to use a fixed phone line for a number of reasons, one of them being this one in question. Another is power-outages – who you gonna call? Unless you want to make a pricey mobile call.

    Reply
  5. One other thought to throw in the mix – I have seen several situations where these 2 wireless devices can be impacted by a wireless mouse as well. When the usb dongle is too close to the cordless phone the mouse can stop functioning properly too.

    Moral of the story? Near your computer, use a corded phone with a speaker or a wired headset. After all, who wants to spend 30 min talking to tech support while craning their neck sideways to hold a cordless phone in place?

    Jon

    Reply
  6. 802.11b is compatible with 802.11g and therefore uses the same frequency. Perhaps its possible to edit the article to read 802.11b/g as these days all new devices are either 802.11g or 802.11n (which I think is also b/g compatible but supposedly offers 125Mbps max throughput).

    Wireless G is most common at the moment with all new laptop and most new computers sold with it by default. All public wi-fi hotspots are also wireless G its only people who bought equipment 6+ years ago when Wi-fi first came out who will still be using B. Either way for the purposes of this article and interferance with cordless phones there is no difference between B & G (thus for clarity the article should probably include both)

    Reply
  7. A: 802.11b works when no other protocol will.
    B. Unless you constantly transfer large files from computer to computer on the same local network, anything above 802.11b is a waste of time and expense, as your cable or DSL is less than half (a quarter?) the speed of even slow 802.11b.
    C. 802.11n usually works in the same room, but reliability gets compromised by every wall, structure, tree, car, couch or any other item between you and the router. Other than self-gratification of having the hottest bestest more than your friends, N tends to make flakey connections. I have to turn N off frequently just so my customers can actually function with wireless internet through their home/office. B works everywhere. G usually does. N, ehhhh, hope we get it.
    D. Local coffee house. Everytime the phone rang, the internet connect was reset. We tried other routers, all channels, B, G whatever. They had to ditch that phone before it was fixed.

    Reply

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