Guess this is why the virus in Hackers sang "Row row row your boat".

August 3, 2008 1:44 AM

Why do some yachts mess with my wifi network?

I live right next to a canal, and especially in the summer a lot of boats pass through it, about 5 meters from my window. Some percentage of those are small yachts, and some percentage of those passing yachts kill my wifi.

On my Mac I see this as the wifi signal icon turning grey for a bit (a few seconds). I stream my music to my speakers over Airtunes, so this usually makes the music stop completely, unless the "jamming" is so short that iTunes recovers and starts playing again after 5 seconds or so.

I don't think there's anything I can do about it except move, and it's only a minor annoyance because it doesn't happen very often, but I am wondering what it is in these boats that messes with my signal. GPS? Radar? Radio? And why is it only a small percentage of yachts that do this?

posted by Skyanth to grab bag (10 answers total)

Wi-Fi of the most common sort, is famously on the same frequency as microwave ovens, but I doubt they'd all happen to be cooking as they passed by. Radar is my bet, as yachts would be equipped with that and it's around the right frequency range.

GPS is receive-only so it wouldn't be that.
It's really surprising to me how few people know how GPS works. There are a bunch of geostationary satellites, each broadcasting a stream of timecode in synch with the others. A GPS receiver just has to work out the time offsets between the received streams from the handful of satellites it can see, and that gives a position in 3D space.
posted by w0mbat at 2:07 AM on August 3, 2008

Radars use the same 2.4 GHz band. You could switch to 802.11a wireless cards which use the 5 GHz band.
posted by stereo at 3:43 AM on August 3, 2008

note that if your Macs are new enough (i.e. of the Intel variety, for the most part), they all support 802.11a anyway. also, 802.11n uses the 5GHz bands too. this includes the new n-capable AirPort Express (which you seem to be using) and the Extreme, but not the older g-only ones.

i wouldn't rule out the possibility that the yachts have wifi on them as well, or walkie-talkies/phones. a powerful enough base station on the same channel as yours can potentially step on your signal. you could use something like KisMAC to verify this (it'll show you what's going on with wifi around you). also, a lot of cordless phones (and this is especially true for older ones that are stupider than newer, post-WiFi-everywhere ones) and walkietalkies use the 2.4GHz band and can also potentially interfere with your wireless. there's a lot of stuff out there that uses 2.4GHz and there's not a whole lotta space in there.
posted by mrg at 3:57 AM on August 3, 2008

I doubt that it is Marine two-way radios (which operate on VHF frequencies centered around 156.8 MHz). Do your speakers pick up any garbled speech sounds as the canal traffic passes your canal? I rather suspect the Wi-Fi system itself which operate on UHF frequencies in the 2.4 GHz band.

Some marine radars operate in the 2.4 GHz area but it's unlikely they would be used in a canal unless in thick fog.

Wikipedia to the rescue:

"Wi-Fi pollution, or an excessive number of access points in the area, especially on the same or neighboring channel, can prevent access and interfere with the use of other access points by others, caused by overlapping channels in the 802.11g/b spectrum, as well as with decreased signal-to-noise ratio (SNR) between access points.

This can be a problem in high-density areas, such as large apartment complexes or office buildings with many Wi-Fi access points. Additionally, other devices use the 2.4 GHz band: microwave ovens, security cameras, Bluetooth devices and (in some countries) Amateur radio, video senders, cordless phones and baby monitors, all of which can cause significant additional interference."
posted by lungtaworld at 4:29 AM on August 3, 2008

Some marine radars operate in the 2.4 GHz area but it's unlikely they would be used in a canal unless in thick fog.

In my experience, no one turns any of the boat's equipment off unless they're docked.
posted by smackfu at 8:45 AM on August 3, 2008

bit of a long shot, but don't small yachts use those corner cube reflectors so that they can be easily seen on radar? they are designed so they refelect radio back directly to wherever it was coming from (very cool). to a wifi router this would appear as another router, transmitting identically, on the far side of the yacht. that might be enough to confuse the router.
posted by not sure this is a good idea at 9:15 AM on August 3, 2008

If it's just your local wi-fi network that's affected, then what others have said. If it's your actual wi-fi connection to the Internet that's affected, then another possibility is that the yacht is blocking the path between you and the wi-fi access point. (Although yachts are often made of wood and fiberglass, they would still greatly attenuate the signal.)
posted by exphysicist345 at 11:56 AM on August 3, 2008

You can mount one of these onto your router and hope the added gain beats off the interference.
posted by damn dirty ape at 2:27 PM on August 3, 2008

Wow, I always wondered how reflectors worked.
posted by kindall at 6:14 PM on August 3, 2008

You can mount one of these onto your router and hope the added gain beats off the interference.

But the added gain would make the router more susceptible, on the receive side of things, to picking up interference.

S-band radar is apparently in the "2-4 GHz" range (that's quite a range...). 802.11b/g is ~2.45 GHz, so radar is my guess.

I'll gladly trade places with you. No boats will come within a few hours of you.
posted by fogster at 7:07 PM on August 3, 2008