Weird interference discovered

Archived from groups: alt.internet.wireless (More info?)

My wi-fi connection intermittently dropped to almost nothing. This
annoyance occurred seemingly randomly and infrequently. It did occur
enough to be irritating, so I checked around the house for things that
could cause this behavour. I dont have a microwave or a cordless phone
so I was stumped.

Then today the neighbour in the apartment/flat opposite received cold
callers (as did I) when I noticed it was her 'wireless' doorbell that
was causing the connection drop. Weird, but true.

Amazingly she agreed to change it to a wired one, on provision I paid
and fitted it. I cant argue with that. I find it amazing that that was
the cause of the problem. I tried it a number of times and sure enough,
each time I pushed the doorbell, the connection was lost.
--
MCR
MAME - History In The Making
www.lazarus.org.uk
www.pleasuredome.org.uk
4 answers Last reply
More about weird interference discovered
  1. Archived from groups: alt.internet.wireless (More info?)

    On Fri, 25 Jun 2004 10:11:58 +0000 (UTC), MCR
    <mcr@nospamtombstones.org.uk> wrote:

    >My wi-fi connection intermittently dropped to almost nothing. This
    >annoyance occurred seemingly randomly and infrequently. It did occur
    >enough to be irritating, so I checked around the house for things that
    >could cause this behavour. I dont have a microwave or a cordless phone
    >so I was stumped.
    >
    >Then today the neighbour in the apartment/flat opposite received cold
    >callers (as did I) when I noticed it was her 'wireless' doorbell that
    >was causing the connection drop. Weird, but true.
    >
    >Amazingly she agreed to change it to a wired one, on provision I paid
    >and fitted it. I cant argue with that. I find it amazing that that was
    >the cause of the problem. I tried it a number of times and sure enough,
    >each time I pushed the doorbell, the connection was lost.

    Amazing. Most wireless doorbells run on 433.925, 418, and 315MHz with
    single carrier OOK (on-off keying). I'm not familiar with UK models.
    It should not have substantial harmonics in the 2.4GHz region and
    those should not have a noticeable effect on 2.4GHz traffic. To the
    best of my knowledge, there are no Wi-Fi wireless doorbells.

    Was this doorbell perhaps part of some Wi-Fi connected burglar alarm
    system?

    Could I trouble you for the model numbers of the doorbell and wireless
    router/bridge? I'm more interested in the router/bridge being
    affected. I guess(tm) that perhaps the CCA (clear channel
    assessment) feature of 802.11g is overly sensitive or easily confused.


    --
    Jeff Liebermann jeffl@comix.santa-cruz.ca.us
    150 Felker St #D 831-336-2558
    Santa Cruz CA 95060 AE6KS
  2. Archived from groups: alt.internet.wireless (More info?)

    Jeff Liebermann wrote:
    Snipped


    > Amazing. Most wireless doorbells run on 433.925, 418, and 315MHz with
    > single carrier OOK (on-off keying). I'm not familiar with UK models.
    > It should not have substantial harmonics in the 2.4GHz region and
    > those should not have a noticeable effect on 2.4GHz traffic. To the
    > best of my knowledge, there are no Wi-Fi wireless doorbells.

    Well I am sure they dont interact on the same frequency also.. That is
    why it isnt one of the things that I was troubleshooting to begin with.

    I would say that the doorbell was at fault in this case rather than my
    router...

    > Was this doorbell perhaps part of some Wi-Fi connected burglar alarm
    > system?

    Not AFAIK. I dont know the details yet, but when I 'buy' it for another
    I will post the details. She works in B&Q (Superstore) so it is
    reasonable to assume it is one of their home brand ones.

    > Could I trouble you for the model numbers of the doorbell and wireless
    > router/bridge? I'm more interested in the router/bridge being
    > affected. I guess(tm) that perhaps the CCA (clear channel
    > assessment) feature of 802.11g is overly sensitive or easily confused.
    >

    The router is A 2wire 233 router with a PCMCIA Wi-Fi card on the front
    (2wire branded).
    The channel is set to 6 (Default). It's 802.11b btw.#


    --
    MCR
    MAME - History In The Making
    www.lazarus.org.uk
    www.pleasuredome.org.uk
  3. Archived from groups: alt.internet.wireless (More info?)

    On Fri, 25 Jun 2004 18:16:02 +0000 (UTC), MCR
    <mcr@nospamtombstones.org.uk> wrote:

    >Well I am sure they dont interact on the same frequency also.. That is
    >why it isnt one of the things that I was troubleshooting to begin with.

    I just happen to have a wireless doorbell here. 433.925MHz. No
    manufacturer name or model visible. I looked at it on my antique
    HP141 spectrum analyzer and it was clean with almost no harmonics.
    My guess is a SAW (surface accoustic wave) oscillator which is rather
    clean in output. I haven't pryed it open yet. Does not affect my
    home router (Linksys BEFW11S4) as far as I can tell. You're might be
    different.

    >I would say that the doorbell was at fault in this case rather than my
    >router...

    The first step to solving a problem is not to assign the blame. If
    there are any other wireless routers available in the building, it
    would be interesting to check if they are similarly affected. Same
    with additional wireless doorbells. It's possible that doorbell
    transmitter might be defective and unique by oscillating in the 2.4Ghz
    band. I've seen stranger sources of spread spectrum intereference
    (GPS vs TV amplfier):
    http://www.gpsworld.com/gpsworld/article/articleDetail.jsp?id=43404
    and susceptibility issues such an unfiltered wireless receiver front
    end with a truely horrible 20 or 30dB dynamic range which would
    overload on almost any RF signal, regardless of frequency. Don't
    assume it's the doorbell until you're sure it's not the 2wire router.

    >The router is A 2wire 233 router with a PCMCIA Wi-Fi card on the front
    >(2wire branded).
    >The channel is set to 6 (Default). It's 802.11b btw.#

    That eliminates the possibility of an 802.11g related CCA problem.

    Hmmm... are you able to use a different wireless card in the 2wire
    router? If so, that might be worth trying.

    I agree. Wierd.

    --
    Jeff Liebermann jeffl@comix.santa-cruz.ca.us
    150 Felker St #D 831-336-2558
    Santa Cruz CA 95060 AE6KS
  4. Archived from groups: alt.internet.wireless (More info?)

    6th harmonic of the 418 MHz range in close proximity (" the neighbour in
    the apartment/flat opposite")...
    N9TGW
    "Jeff Liebermann" <jeffl@comix.santa-cruz.ca.us> wrote in message
    news:bggod09fvncq114m675jq8irvn7jjjvnpl@4ax.com...
    > On Fri, 25 Jun 2004 10:11:58 +0000 (UTC), MCR
    > <mcr@nospamtombstones.org.uk> wrote:
    >
    > >My wi-fi connection intermittently dropped to almost nothing. This
    > >annoyance occurred seemingly randomly and infrequently. It did occur
    > >enough to be irritating, so I checked around the house for things that
    > >could cause this behavour. I dont have a microwave or a cordless phone
    > >so I was stumped.
    > >
    > >Then today the neighbour in the apartment/flat opposite received cold
    > >callers (as did I) when I noticed it was her 'wireless' doorbell that
    > >was causing the connection drop. Weird, but true.
    > >
    > >Amazingly she agreed to change it to a wired one, on provision I paid
    > >and fitted it. I cant argue with that. I find it amazing that that was
    > >the cause of the problem. I tried it a number of times and sure enough,
    > >each time I pushed the doorbell, the connection was lost.
    >
    > Amazing. Most wireless doorbells run on 433.925, 418, and 315MHz with
    > single carrier OOK (on-off keying). I'm not familiar with UK models.
    > It should not have substantial harmonics in the 2.4GHz region and
    > those should not have a noticeable effect on 2.4GHz traffic. To the
    > best of my knowledge, there are no Wi-Fi wireless doorbells.
    >
    > Was this doorbell perhaps part of some Wi-Fi connected burglar alarm
    > system?
    >
    > Could I trouble you for the model numbers of the doorbell and wireless
    > router/bridge? I'm more interested in the router/bridge being
    > affected. I guess(tm) that perhaps the CCA (clear channel
    > assessment) feature of 802.11g is overly sensitive or easily confused.
    >
    >
    > --
    > Jeff Liebermann jeffl@comix.santa-cruz.ca.us
    > 150 Felker St #D 831-336-2558
    > Santa Cruz CA 95060 AE6KS
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