Why do fluorescent lights mess up my WiFi signal?

Recently, a reader emailed me with a question that stumped me for a bit. He had noticed that fluorescent lights seemed to degrade his wifi signal. I had heard that before but only in passing. His question was a simple “why?”

Ultimately, I ended up talking to an electromagnetics PhD over it. He broke it down into fairly simple terms for me.
As discussed in a previous article, thermionic emission occurs in the lamp portion of a fluorescent light bulb. This occurs as an arc passes through the mercury vapor present in the lamp. One side effect of this is the production of radio waves up to a few megahertz in frequency.

Modulation of a lower frequency sinusoidal wave by a higher frequency signal.
Photo credit: La Trobe University

Wifi operates on radio waves at about 2.4 or 5Ghz.
Now I know what you’re thinking because I was thinking the same thing (electromagnetics is my weak point). How does a relatively lower frequency disrupt a much higher frequency signal? Turns out, the relatively weaker Wifi signal will still feel the effects of “cross-talk” from the locally stronger radio waves effecting it. It is possible that the Wifi signal will get picked up as modulation for what is basically a lower frequency carrier wave.
Another much more simple possibility is that destructive interference is happening often enough to cause dropped message packets between the computer and the router. Sure, you wouldn’t expect it to happen that often since the frequencies are mismatched by such a large amount but it doesn’t have to happen often to be a nuisance. Packets get dropped whenever bits are missing based on a checksum test of each packet that arrives. Corrupted data? Your packet gets thrown away. Either way, your Internet experience suffers. Thanks, physics. All possible explanations boil down to different types of electromagnetic interference causing problems with your wifi reception.
For further reading on lighting systems, check out this article on LED lighting.

12 Responses

  1. Tyler
    Tyler at |

    From one Tyler to another, THANKS! for some time now when my mom goes to bed and has her lamp on and tv (old box tv) my internet would go out. for the longest time I thought it was her old tv emitting some frequency that was disrupting it, but last night my internet came back when she turned her lamp off (tv still on) which really stumped me. tonight same thing happened and sure enough my internet came straight back as soon as the lamp was off. google led me here to end the insanity.

  2. Barry Barnes
    Barry Barnes at |

    I also have a real big problem, I have been supplied a new hub and 3 new Hotspot extenders but the problem as follows still exists.
    I just realised last night that it appears that it seems that in the evening only, when we use table lamps fitted with the new flurescent plugged into the power sockets, I lose the ethernet connection to the TV and my I Pad.
    I think I hit on the problem, and I think you have confirmed it, I will try tonight without the lamps on, thank you.
    Regards, unhappy Barry

  3. Barry Barnes
    Barry Barnes at |

    I left a message earlier but forgot to enquire if you think the followin has any effect. My Hub was set up for my TV which is in another room, for 2.4GHz instead of the 5GHz optoon, will this have any effect on losing signal from the fluorescent lamps??
    KR, unhappy Barry

  4. Barry Barnes
    Barry Barnes at |

    Hi Tyler,
    I also have problems as described by the other Tyler. After complaining, I have been sent a replacement new Hub and extender set but still have drop outs on the extender only at night, however no probIems in the room where the hub is. I thought only last night could it be an influence of our table lamps which are flourescent and used only at night where the extender is based. Then today I read your information and think maybe I was right. Our tv is set for 2.4GHz while my PC based in the room where the hub is set for 5GHz. The tv is connected to the extender using an ethernet cable and my tablet by wifi of course but still fail at night.
    I would appreciate you comments.

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