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Dect 6.0 cordless phone interferes with wireless... what phones don't ???

I bought a dect 6.0 phone specifically because it advertised as not interfering with wireless LANs. Well guess what... it takes my 1.2MB wireless connection down to dial up speeds (and it's definitely the phone- when unplugged, the wireless comes right back up). There's very little info out there on what phones don't whack wireless LANs (as opposed to vice-versa). Before i waste another $70, anyone have recommendations for cordless phones (either ghz speeds/types or specific phones) that neither interfere with -nor from- wireless network? I've got to have a cordless phone because there is only one phone jack in my house.
And would upgrading my router help? it's an older (3 years?)Actiontec wireless/DSL modem.

PowerBook G4, iMac G4, iBook G4, Pismo and MORE, Mac OS X (10.4.7)

Posted on Jan 6, 2008 8:15 PM

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8 replies

Jan 6, 2008 8:44 PM in response to lisajoy

Hi lisajoy: From your post I get the impression that the cordless phone interferes with the router, even when it is not in use. This makes me think there is some other issue happening. You say there is only one phone jack, does it have a working DSL filter on that jack prior to the phone cord? Was this an issue with other phones, wired or wireless? It is also possible that the line is filtered outside the house.

Stedman

Jan 6, 2008 9:35 PM in response to lisajoy

Given that the [802.11 b/g/n wireless networks|http://en.wikipedia.org/wiki/IEEE_802.11] operate at a frequency band of 2.4GHz, under some conditions a long-range cordless phone can cause some interference if it uses the same frequency. The original cordless phones used 800MHz, then they came out at 2.4GHz and the newer models now use the 5.2GHz band. In this last case, there could be interference with the old 802.11a and the alternate band for 802.11n, although the technology for the n standard (which is interim for now) incorporates interference reduction mechanisms not found in older standards. To be on the safe side, I would opt either for the older models or the very latest; most phones will say somewhere in the box at what frequency band they operate.

Also worthy of noting is that Bluetooth uses the same frequency band and has been mistakenly blamed for interference. However, it uses much lower power and a frequency hopping multiplexing technique and cannot interfere with 802.11b/g/n.

If you want to get real technical, there's a cute gadget called the [WiSpy spectrum analyzer|http://www.metageek.net> that can give you a graphical view of how your wireless devices interact in their frequency bands. However, the Lite version goes for $200 and the Pro model for $400, so this is strictly for hardcore geeks... 😉

Jan 6, 2008 11:31 PM in response to Courcoul

Sorry, slight imprecision. The frequency bands allocated for cordless phone use are 800MHz, 2.4GHz and 5.8GHz. Hence, the only overlapping and possible interference is in the 2.4GHz band shared with 802.11 b/g/n networking. The new [DECT 6.0 cordless phone standard|http://en.wikipedia.org/wiki/DECT] has been allocated the 1.920 to 1.930GHz band in the US, so it should cause no interference at all.

Jan 7, 2008 2:32 PM in response to Courcoul

yeah, the 6.0 shouldn't cause interference... and maybe it isn't. the slowness is now back, even with that phone still unplugged, tho it's more sporadic.
But originally the speeds instantly went back up when i unplugged that phone (dramatically, from 100kbps to 1100+). Now it's bopping between low 100s to low 1000s, inconsistently, but mostly around 300kbps. Signal is a full four bars.
No other cordless phones or wireless anything in house... but i have three neighbors within 50 feet. None have wireless that shows up in my Airport menu, but they may have phones.

So i've got multiple sources of interference, or something else is going on.
argggh! taking the modem back to my ISP's tech for yet another channel reset. He pretty much flatly refuses to consider the WPA possibility. I'm not sure if the modem/router is "n" standard- it's a three year old Actiontec DSL modem with wireless.

Jan 8, 2008 4:17 PM in response to lisajoy

ok, this is interesting. My slowness issue turned out to be a bad wireless card in the modem itself, not interference. BUT... in the course of things, my ISP tech came over with an interference sniffer (WiSpy, really cool lil thing!) and it showed that the GE Dect 6.0 phone did indeed interfere significantly. A cheap 5.8ghz Vtech phone we tried didn't even show up in the scan, zero interference. The tech was mystified too, said the Dect (which is supposed to be at 1.9ghz) shouldn't have been a problem... but it was.
So there ya go... Dect 6.0 phones might not be all they're cracked up to be.

PS, that GE Dect 6.0 had crappy sound and volume, too... avoid them.

Jan 8, 2008 10:37 PM in response to lisajoy

Cool that you got the problem solved.

I'll have to test my Vtech Dect 6.0 phone at home with the WiSpy, now that you mention it. Since I use a patchcord at home to keep the wireless card on my 2Wire ADSL off (got tired of seeing the neighbors keep trying to crack it constantly), I never even thought of sniffing on the phone. Good point.

Hope you enjoyed your WiFi whodunnit adventure! 😀

Dect 6.0 cordless phone interferes with wireless... what phones don't ???

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