Can DECT Phones interfere with Broadband?
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Can DECT Phones interfere with Broadband?
14-02-2009 3:24 PM
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However, whilst running routerstats (which uses a wireless connection to telnet to the router every 60 seconds),
I noticed that my noise margin fell from 6dB to 3dB (without any change in sync speed) when a telephone call was made.
It recovers as soon as the phone is returned to the base station.
This effect is quite reproducible.
The router and DECT share a power strip and plug into the two halves of the same filter (different filters have been tried).
Is it possible that a DECT (2.4GHz) can interfere with ADSL (2MHz)?
The two devices are about two feet apart (vertically) and no other re-location is physically possible.
"In The Beginning Was The Word, And The Word Was Aardvark."
Re: Can DECT Phones interfere with Broadband?
14-02-2009 4:16 PM
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It seemed to be the ringing which did the damage so I tried it by phoning in from my mobile while the phone was disconnected and it still happened.
In my case it took a long time to more or less sort it including replacing the line card at the exchange
If it is only with the DECT phone you could try double filtering the phone - for some reason it seemed to help in my case
Re: Can DECT Phones interfere with Broadband?
14-02-2009 4:22 PM
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I'll do that as soon as the "better half" gets off the phone
I'll report back ASAP - which could be hours
"In The Beginning Was The Word, And The Word Was Aardvark."
Re: Can DECT Phones interfere with Broadband?
14-02-2009 5:06 PM
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Re: Can DECT Phones interfere with Broadband?
14-02-2009 5:30 PM
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See the pretty graphs below:-
http://dl.getdropbox.com/u/449229/NoiseMargin-2009Feb14-1504.jpg
and
http://dl.getdropbox.com/u/449229/NoiseMargin-2009Feb14-1720.jpg
Unfortunately that sudden plummet at the end of the second graph was a test carried out by me,
just after double filtering the DECT (but only single filtering the ADSL).
Since noise margin is around 5.5 - 6.5dB in the absence of phone calls, I'd put forward a clear
case for DECT interference,
BTW This is in new D-Link router.
"In The Beginning Was The Word, And The Word Was Aardvark."
Re: Can DECT Phones interfere with Broadband?
14-02-2009 5:32 PM
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Re: Can DECT Phones interfere with Broadband?
14-02-2009 5:44 PM
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Re: Can DECT Phones interfere with Broadband?
14-02-2009 5:48 PM
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Quote from: Oldjim No drop when the phone wasn't connected but you phoned in then
The phone was connected at all times (with the exception of the time it took to stick in an extra filter).
Those periods when the noise margin was below about 5dB were when the phone was lifted out
of it's cradle and in use.
I've had a thought - when the phone is "active" and generating it's 2.4GHz RF - could these interact
with the nearby wireless router and generate harmonics in the 2MHz ADSL region?
Can't say I know much about these things - but it seems a possibility according to
http://en.wikipedia.org/wiki/Hetrodyne#Mathematical_principle
"In The Beginning Was The Word, And The Word Was Aardvark."
Re: Can DECT Phones interfere with Broadband?
14-02-2009 5:52 PM
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Quote from: The I'm convinced!
-----
Since noise margin is around 5.5 - 6.5dB in the absence of phone calls, I'd put forward a clear
case for DECT interference,
You can only come to this conclusion if you do identical tests with a POTS. I have used both DECT and POTS and both increase my SNRM from 12db to 15db. So my conclusion is that DECT phones do not affect the line.
Re: Can DECT Phones interfere with Broadband?
14-02-2009 5:59 PM
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Quote from: The ---
I've had a thought - when the phone is "active" and generating it's 2.4GHz RF - could these interact
with the nearby wireless router and generate harmonics in the 2MHz ADSL region?
DECT phones are transmitting on their carry frequency all the time irrespective whether the phone is being used or not.
Re: Can DECT Phones interfere with Broadband?
14-02-2009 7:17 PM
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I'm using a simple double coupler.
Here are the results:-
(The DECT was in action in the early part of this graph) - and finally fell to zero, which has knocked my speed back a bit
The DECT was hung up fairly swiftly and my noise margin shot up to 8+dB
The fall from 8.3dB to about 6dB was caused by the POTS corded phone.
Subsequent climb back to 7.5 dB was with all phones back on-hook.
Why is this happening - I haven't changed my phone for many years.
http://dl.getdropbox.com/u/449229/NoiseMargin-2009Feb14-1915.jpg
"In The Beginning Was The Word, And The Word Was Aardvark."
Re: Can DECT Phones interfere with Broadband?
14-02-2009 7:23 PM
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Re: Can DECT Phones interfere with Broadband?
14-02-2009 7:37 PM
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router sync speed dropped from 5766Kbps to 5407Kbps then I must have
I have detailed stats from the log file:-
Quote Sat 14 Feb 2009 18:49:32, Noise Margin= 5.9, Sync Speed= 5766
Sat 14 Feb 2009 18:50:32, Noise Margin= , Sync Speed=
Sat 14 Feb 2009 18:52:22, Noise Margin= 6.7, Sync Speed= 5407
I haven't revealed these until now - I've got lots!
"In The Beginning Was The Word, And The Word Was Aardvark."
Re: Can DECT Phones interfere with Broadband?
25-03-2009 8:14 AM
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Re: Can DECT Phones interfere with Broadband?
25-03-2009 12:44 PM
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Since then I have fitted an i-plate (which prevents interference from any source using the bell wire as an aerial and feeding it into my ADSL signal).
I have used routerstatslite to monitor noise margin with a resolution of 0.1dB
Using a DECT or a wired phone is undetectable within the medium term natural variation of +/- 0.2dB of noise.
So - DECT doesn't now affect my signal (if it ever did) - although it can do for some people.
"In The Beginning Was The Word, And The Word Was Aardvark."
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