Crackling/interference on Cordless phones

sjedmonds

I'm hoping someone can help me. Over the last few months we had been experiencing severe crackling on our phone line (BT). We couldn't hear it but the person on the other end could and it was different numbers/callers as well. I changed the phone (5yr old Panasonic dect phone) for a BT Synergy 4500 trio and the base station is in my dining room, plugged into the ADSL filter straight into the socket. I also changed the ADSL filter. Still getting the noise. Called out BT - they did quiet line check etc, checked their exchange equipment, but it is still happening. Tried an old corded phone and the line is much quieter. Is there any way of finding out what is causing the interference or an expert I can call in (am based in north east london)? I made a call this morning and the only other piece of equipment that was on was my computer and the TV downstairs. We have Sky+ but that is in a different room to the base station.
Have read up some info and see that there are phones that use 5.8Ghz instead of the standard 2.4. Is it worth spending more money on one of these to eliminate the problem?
Any help would be much appreciated.
Sharron

kwikbreaks

One thing worth trying is to make calls with your router turned off and check. There is a type of line fault which causes a line to be noisy when it is carrying an ADSL signal. BT should by rights have checked that out already but they may have just disconnected all your equipment.

Then you need to check with a standard corded phone - if that is OK then yes the problem is with your DECT phone and as it is new take it back to the shop for replacement.

Regarding the transmission frequency - I don't believe it will make any difference. The clue is in the name DECT - that D stands for digital and interference to a digital link doesn't typically produce crackling which tends to be an analogue problem.

As you've had the problem with two different phones already and changed your ADSL filter my betting is on the line fault I first mentioned. It would also probably impact your ADSL so post up the router stats too for checking if they look correct.

sjedmonds

Hi - thanks for your input. I have already tried a corded phone and the line is quieter then when we put back the DECT phone, it started again.

The ADSL filter set up was checked by the BT engineer and I have changed the filter as well. Also, the engineer said that if the interference was the broadband, it would produce a different noise to crackling anyway.

My broadband router is a Netgear DG834G. I have one computer connected to it via a cable, then my other computer upstairs connects via wireless. It doesn't seem to make a difference if the router is on or not to the phone noise.

kwikbreaks

> It doesn't seem to make a difference if the router is on or not to the phone noise.

In that case it isn't the fault I suspected. If the filter goes dodgy then it doesn't produce a crackle but the type of line fault I suspected can.

The noise is possibly being picked up by the dect base unit - try moving it to see if that changes anything.

sjedmonds

Thanks, I will move the base station (may have to get an extension though) and let you know if things improve.
Many thanks for your help.

kwikbreaks

You're welcome. I hope moving it will help as there seems little else to try.

isofa

I notice it's a wireless router? Although you've ruled out the router when plugged into the phone line, wi-fi signals do operate in the same space as DECT phones, and can interfere.

A client of mine with many wireless repeaters around their building is completely unable to use their cordless phones due to interference.

Try changing the channel on the cordless phone (info should be in the instructions), it might have the option for a couple of different channels.

kwikbreaks

I've never come across a DECT phone that offers the ability to choose a channel.

Frequency:
1880 MHz–1900 MHz in Europe,
1900 MHz-1920 MHz in China,
1910 MHz-1930 MHz in Latin America and
1920 MHz–1930 MHz in the US

http://en.wikipedia.org/wiki/DECT

isofa

^ I think you are right kwikbreaks, they are dynamically setup, was thinking of older analogue cordless phones, I'm sure I saw the option in our panasonic menu, but I suspect it was a "join to group" setting for registered third party DECT handsets.

Still wifi and DECT does interfere...

kwikbreaks

You are thinking of the old pre-DECT phones. Some did operate in the 2.4GHHz band and had fixed channels. DECT phones select their own channels each time they are used and operate in the frequency bands I posted above from Wikipedia.

TV senders can screw up WiFi and vice versa but the problem here is with the DECT phones and as they are digital interference will not sound like crackling. WiFi and DECT are such commonly used technologies if there was a conflict these boards would be full of tales of woe.

If there is crackling and it isn't on the actual phone line I think it must be being picked up by the analogue audio circuitry in the base station. It could be that the WiFi signal is being rectified there but as that operates on low power (100mw max I think) I'm inclined to suspect it is something else.

sjedmonds

The noise is still there even when the router is turned off at the mains.