wifi interference

Wifi interference caused by BTWiFi and BTWifi with FON (BT Infinity)

Ever since doubling down on my broadband connection by using both Virgin Media and BT Infinity my wired connection is amazingly fast.. almost supersonic.  But after a few days, my wifi connection really started to suffer.  And the problem wasn’t just with my wifi – my Sonos system started to drop out intermittently and it doesn’t use a standard wifi signal.  Everything pointed to some form interference.. I live in a city and so there are plenty of other wifi signals around.. here’s what I found:

BT Wifi Interference

Quite a few access points – but the most worrying was the BTWifi and BTWifi-with-FON signals.  I run my own ASUS wifi router and so had disabled the wifi signal on both the Virgin and BT boxes.  But these signals were too strong to be a neighbour – they were originating from the BT Infinity box.  I did some digging, and here’s what I found.

BT Infinity offers an “opt out” service called BTWifi with FON.  Everyone who subscribes to BT Infinity automatically gets access to a national “grid” of wifi access points – all powered by the BT Infinity router in people’s homes.  It means that in exchange for sharing some of your bandwidth with the public, you get access to the same.. wherever you go.  A pretty clever idea in principle.. but what they don’t tell you is that your BT Infinity router has 3 networks being broadcast all the time – one for your private network, one for BTWifi, and one for BTWifi-with-FON.  All three on the 2.4Ghz frequency.  If you then have a couple of neighbours running the same, then each of them will also have three networks.  And so on and so on.

My own wifi issues were killing me and the fact that Sonos was dropping out too was the last straw.  To disable these signals, you have to “opt out” from the BT Wifi site – this is in addition to disabling the wifi signal on the BT router.  It’s not too complicated, here’s how:

1. Head to the BT Fon site

2. Click on the “Check Status” button

3. Enter the login details that BT sent you – these will be in an email with  “Your BT service is ready: see what’s next” in the subject.  The email address will end in “@btinternet.com”

4. Click on the “Check Status” button (again)

5. Go to the “Opt Out” section

6. Enter your login details again.. and press “Send”

7. You will then get a notification saying that it will take up to 48 hours.. and to leave your router on.

I ran this in the morning and checked again when I got home – and now the BTWifi and BTWifi-with-FON networks were gone.. and my own WiFi is back on top:

BT Wifi no interference

More importantly, my wifi has never been faster – all over the house.. reaching 70Mbps to 80Mbps three floors down.. where before I might achieve 10/20Mbps when it was behaving or 1Mbps when it wasn’t.

I don’t think I ever appreciated the huge negative impact that interference can have on your wifi performance.. and so if your network is suffering, I highly recommend you take a look at what other networks (and devices) are near you that could be having an impact.  And if you have BT Infinity – opt-out of the BTWifi with FON option.




8 Responses to Wifi interference caused by BTWiFi and BTWifi with FON (BT Infinity)

  1. Allan September 27, 2013 at 2:23 pm #

    This just shows the problems the BTFON and BTWIFI generate with their own users but what about the people who are on different systems? I am on Talk Talk but I am surrounded by numerous BTFON/WIFI users in my street and the nearest ones overpower my router and ‘lock on’ almost before my laptop has finished booting so instead of being connected to my Talktalk ISP I am connected to the nearest BTWIFI which is some distance away as its signal strength is 60dbm while mine is 48dbm.
    Even using third party software I cannot block out the BT logins and so I first have to disconnect from the BT source before I can try to connect to Talktalk. I find this most annoying and would appreciate any suggestions to block my computer from picking up BTWIFI/FON signals

  2. 1MattHopkins September 27, 2013 at 3:19 pm #

    Totally agree – I have similar issues near me, but not so bad that neighbours are interfering with my signal. The whole BTFON with WIFI concept is a nice idea but poorly implemented if you ask me.

  3. Ian December 1, 2013 at 7:39 pm #

    Good post, what app are the screenshots from? The one app I had like that didn’t give nearly as much detail. Thanks!

  4. 1MattHopkins December 1, 2013 at 10:27 pm #

    Hi Ian – thanks for commenting. The screenshots are from an app called WiFi Explorer – here’s the link: https://itunes.apple.com/us/app/wifi-explorer/id494803304

  5. DanOlner December 2, 2014 at 2:12 pm #

    Just come across this post, having spent a while trying to track down where the interfering signals were coming from using wifi analyzer. BT helpline were useless, I didn’t know about the router being used as a hotspot – we’d change the channel, and two other channels (I thought were neighbours!) would change too – which is impossible, it was very confusing! The Bt FON page says they’re on different channels – not true, they change together, which is colossally dumb.

    Now in the process of opting out. Deeply unimpressed with BT on this. Thanks for the post.

  6. Lynda April 20, 2016 at 10:48 am #

    Apparently opting out of BT WIFI with FON does not stop the BTHomehub 4 from transmitting a 5GHz FON signal (hotspot). It stays on whether you opt out or not? As per another forum? Would really like to know the answer to this. BT no help.

  7. Paul July 9, 2016 at 12:13 pm #

    I have also suffered from a related issue where my home WIFI signals suffered from interference in evenings and cause my overall broadband speed (through WIFI) to drop from a normal 27mbps down to around 4-5mbps. If I plugged the laptop straight into the back of the router, performance was fine and peaking at 27mbps. I was originally automatically opted in as an Infinity user. I hadn’t realised at the time that extra BT WIFI SSID’s were started on my home router. In the meantime to try and address the performance issue, I configured the router to transmit two separate SSID’s for the 2.4ghx and 5ghx ranges. When using a WIFI monitor program, called INNSIDER, I noticed that my home router was actually transmitting an additional 4 BT WIFI SSID’s (2 for the 2.4ghx SSID and 2 for the 5ghx SSID) using the same channels as the parent SSID. The INNSIDER program also allow me to confirm my SSID’s were not using the same channels as SSID’s transmitted by other routers close by.

    In the hope that this was potential causing my dip in speed during the evenings, I contacted BT. It’s took about 1-2 months to completely opt out of the BT WIFI with FON scheme. The initial opt out process took place over the internet and was straight forward and quick, but it still left the 4 extra SSID’s running on my router. After a further 5 phone calls with BT, I eventually got through to someone who knew what to do, and within 3 hours the additional SSID’s were disabled and I was fully opted out.

    The WIFI speed in evening now seems to remain at around 20-27mbps so I’m a lot happier now. Those BT WIFI SSID’s definitely impact your home WIFI performance.

  8. Matt Hopkins July 9, 2016 at 12:58 pm #

    Thanks Paul. I’ll have to take a look at that innsider app.

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