Troubleshooting a Slow or Intermittent Broadband connection

Published 12/05/2004 11:05   |    Updated 22/04/2009 12:36
What can I do to improve my BT Broadband connection?

If your broadband connection appears to be slow or intermittent there are a number of things to check before reporting a fault to BT.


Step 1: Use Microfilters and avoid using extension cables

Always ensure that you have a microfilter attached to every phone socket in your house. Click here to find out why microfilters are necessary and how to install them correctly.

The most common cause of a poor broadband service is the use of poor quality telephone extension cables. This is because they are more prone to electrical interference, which causes BT Broadband to reduce data speeds to compensate. Avoid using extension cables or extension sockets.

If this is not possible, we recommend that you keep any extension wiring as short as possible, use copper rather than aluminium extension leads, and route them to avoid areas of electrical interference such as near power cables, digital phones, microwave ovens, Christmas tree lights, high-wattage equipment, and halogen lighting etc.

If the problem persists then you should consider using an extended Ethernet cable or a wireless router.


Step 2: Use an Ethernet cable, reinstall USB drivers, update Voyager firmware.

If you are using a BT supplied router/modem then you should use the supplied Ethernet cable (yellow) rather than the USB cable (blue). If there is a problem with the USB driver software it can effect your ability to connect to the Internet. Click here for detailed instructions on how to connect your router to your computer using an Ethernet cable.

If your computer does not have an Ethernet port then you should reinstall the USB driver software used to operate the modem. Click here to download the latest USB drivers for your BT supplied modem. If you are using a non-BT supplied modem with a USB cable then contact your manufacturer's website for further advice.

If you are using a BT Voyager router click here for instructions about an important firmware upgrade recommended for all users.


Step 3: Check your broadband connection (line) speed

Your connection speed (or 'line rate') is the speed of your phone line between your router or modem and the local exchange. It is determined principally by the length of your line and its condition. Note that old wiring is more susceptible to interference and faults.

You can find out your line's synchronisation speed by accessing your router or modem's configuration pages. If you are using a BT supplied router click here for detailed instructions on how to obtain and understand these statistics.

If you are using a router not supplied by BT please refer to the instruction manual. Be careful not to change any of your router's settings. Look for the term 'connection speed', 'line speed' or 'line rate', which will usually be shown in Megabits or Kilobits per second (Mbps or Kbps). Please note this speed for later comparison purposes.


Step 4: Check for faulty microfilters or phone equipment

Unplug all your devices connected to the phone line including broadband microfilters, corded & cordless phones, fax machines, Sky digi-boxes etc. Plug your router/modem into your master telephone socket without using a microfilter. The master phone socket is usually the one closest to the front door.


If you have a phone master socket like the one in the photo (that is, square with a horizontal groove halfway down it and removable upper and lower cover) then click here and follow the instructions that will enable you to rule out a possible fault with your internal wiring.


Restart your router/modem (switch off, wait 30 seconds, then switch on), wait until it automatically reconnects to Internet, then recheck your connection speed as per Step 3 above. Before taking the speed reading, you must refresh your browser page (press the 'Refresh' button on your browser toolbar). If your synchronisation speed increases, this typically indicates that one of the devices you have removed was generating interference and was causing your broadband service to slow down in order to compensate.

Reconnect your microfilters one-by-one, then reconnect your phone devices one-by-one, repeating between each the speed test described in Step 3 (remembering to refresh your browser each time). Again, if you connect a device which is causing interference, you should see the connection speed drop. You can then double check this by disconnecting the faulty item before repeating the speed test in Step 3. It should revert to its previous speed.

We recommend you leave the faulty device permanently disconnected or arrange to replace it.

If you are using BT supplied microfilters contact our Technical Support centre via phone or email. If you are using non-BT microfilters then you can purchase a replacement from any major electrical or computer store.

If you can hear noise/interference on your telephone handset when making or receiving calls there may be a fault with your phone line that is causing the broadband connections problems. Using your telephone at the master socket with no broadband router or microfilters attached to any socket, make a few phone calls. If the interference persists then you may have a fault with your phone line. To report the fault call 1904 if your line rental is paid to BT, call 1901 if eircom is your line provider.


Step 5: Connection speed Vs. throughput speed

The tests above measure synchronisation speed, the maximum data speed your phone line can support. Fluctuations in it usually indicate possible wiring or interference issues, either in BT's network or your home phone wiring. However, the speed at which you see web pages or download files is determined by more than just the speed of your phone line - it is also governed by the speed of your computer, congestion in the telephone network and on the Internet, and speed of website servers.

This end-to-end speed is measured by throughput speed, the actual rather than maximum speed your data is travelling at in given moment. Throughput is the speed reported by most online speed test websites. It is normal for your throughput speed to reduce significantly between 5pm and 10pm daily, as this is the time when BT network and Internet congestion is at its heaviest (rather like the rush-hour on a motorway).

You check this by carrying out a test on at 7pm (during the peak) and again at 11pm (off-peak) to compare the difference. Note that a slow throughput speed is not generally an indicator of a line fault.

Measuring the transfer rate is also a good indication whether your broadband connection is performing as it should be. Click here for an explanation of what you should expect the transfer rate  to be for each BT Broadband Option.


Step 6: Still having trouble?

If, having followed all of the steps above, you still believe you have a line fault or interference issue, then please contact BT Technical Support on 1890 923 111. Opening hours are outlined below:

Mon-Fri: 8am - 9pm
Sat: 9:30am - 6pm
Bank Holidays: 10am - 7pm
Closed Sundays

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