Last Updated on November 13, 2020 by Dave Farquhar
Long ago, when dinosaurs roamed the earth and knights in shining armor fought them, people had landlines. And they plugged cordless phones into them. Everything was great. Then phones started using the 2.4 GHz and 5 GHz frequencies. Wi-Fi came out using the same frequencies and the two interfered with each other. Now, it seems increasingly difficult to keep cordless phones from interfering with Wi-Fi.
Many people have neatly solved the problem by using cell phones exclusively. But what if that isn’t an option? You’re actually in luck, and you don’t have to dig up a 20-year-old 900 MHz phone and try to find a battery that works in it.
If you’ve ever wondered why Netflix hiccups whenever the phone rings and someone answers it, it’s probably because the phone is running on the same frequency as the box that’s streaming Netflix to your TV. The trick is to find a phone that runs on a different frequency. That isn’t easy if you don’t know what to look for.
For years I just lived with it. I bought 900 MHz phones when I could find them, but keeping them working was a pain. Several years ago my wife got sick of them. She inherited a Uniden 2.4 GHz cordless phone from a relative. It’s worked well for a very long time. Uniden always did make good phones. But now that we’re constantly streaming video all around the house, I set out to make it work better. I had to brush up on phones.
I used to sell phones because I sold computers, and phones were in the same department at that big-box consumer electronics store. But that was way back in 1994. Back then, the new rage was 900 MHz cordless phones. They seem quaint now, but they didn’t interfere with anything else. So when I started looking into current standards, I realized I wasn’t the only one who wanted something that didn’t interfere with anything else.
Enter DECT 6.0
New cordless phones use a standard called DECT 6.0. DECT actually runs at 1.9 GHz, a safe distance away from the two frequencies Wi-Fi uses. So the calls will be clearer and Wi-Fi will run faster and with better range. To people used to hearing that higher is better, 1.9 GHz sounds worse than 2.4 GHz. That’s why they use the DECT 6.0 name instead, to make it sound better than 5 GHz, which it is. A 1.9 GHz frequency has better range than 5 GHz and doesn’t interfere with wireless networking. I’ve compiled a list of cordless phone frequencies if you’re interested.
If you still have a landline service–and if you’re crafty, it’s free or nearly free thanks to devices like the OBi200–it’s not a bad idea to replace old cordless phones with DECT 6.0 phones. The Panasonic KX-TGC352B is a good quality phone and it uses AAA rechargeable batteries. That’s good, since proprietary phone batteries often cost more than a new phone. There are cheaper phones out there–Vtech comes to mind, but I’ve always found Vtech’s quality a bit more uneven than Panasonic. But if you don’t use your phone much, a Vtech CS5119 costs $20 and will do the job, and also uses cheap plain rechargeable AAA batteries.
When the batteries that come with either phone run out, I recommend replacing them with Eneloop AAA batteries for longevity, both between charges and for number of charges.
Call me old-fashioned, but I like having a landline or something VOIP-based that resembles a landline. I don’t like paying for one, but that’s another story for another time.
And that’s how you keep cordless phones from interfering with Wi-Fi.
One last note: If you run DD-WRT, there’s another adjustment you might want to make to help deal with interference and reduce packet errors. You might also want to read about how I beefed up my network with additional access points, or my recommendations for wireless routers.
The reverse problem
OK, I lied. One more last thing, since a great question came in. Can Wi-Fi interfere with cordless phones on the same frequency? I think it can. I have much less trouble hearing on a DECT 6.0 phone than I had on the old 2.4 GHz phone we had. With DECT, the sound is clearer and it’s louder.
I care more about Wi-Fi, since we use Wi-Fi far more than we use the phone, but the problem of Wi-Fi interfering with cordless phones is very real.
David Farquhar is a computer security professional, entrepreneur, and author. He started his career as a part-time computer technician in 1994, worked his way up to system administrator by 1997, and has specialized in vulnerability management since 2013. He invests in real estate on the side and his hobbies include O gauge trains, baseball cards, and retro computers and video games. A University of Missouri graduate, he holds CISSP and Security+ certifications. He lives in St. Louis with his family.