Cordless phone interference has always been a problem–phones interfering with other things, and other things interfering with them.
That was the draw of 900 MHz phones. There wasn’t anything else running on that frequency at the time, so there was little to no interference. But 900 MHz didn’t sound hi-tech in the age of gigahertz computers. So in the early 2000s, 900 MHz gave way to 2.4 GHz and 5 GHz phones. That brought back the problem, because there’s so much other stuff operating at those frequencies these days, like wireless computer networks. But there is a solution that doesn’t involve digging up a 20-year-old 900 MHz phone and trying to find a battery that works in it.
Symptoms of interference include static, unclear voices, or too-soft voices. If your cordless phone doesn’t sound better than a cell phone, you probably have at least some interference.
While there are still some 5 GHz phones out there, there’s also 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.
The Panasonic KX-TGD210N 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 CS6124 costs $22 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.
It does cost a little bit to stop cordless phone interference, but at least you’re not talking a huge purchase. A new phone and a good quality set of batteries does the trick.
If you’re curious about cordless phone standards and frequencies, here’s a list.