Remote monitoring of interference?

Just out of curiosity, what makes you think it is interference from another network, instead of literally hundreds of devices that won't show up in the logs? (example, interference from cordless phones, microwaves, wireless intercoms, industrial sealing equipment - RF plastic heat sealers are absolutely the worst, etc)

Kismet allows remote monitoring, though I haven't used that feature myself. I don't know how the windows version works, but I bet it is a waste of time. I found it (linux source) more difficult than the run of the mill tarball to compile, plus you may need to find code specific to your wifi hardware. Once it works, the program is very impressive. There is an amazing amount of wifi out there that never shows up under netstumbler.

I never said what I thought the source could be. But looking at her office space: it's a pool supply store with rented office suites on both sides of the pool store. I suspect 2.4GHz cordless phones and microwaves, to be honest. In any case my goal is simply to determine whether interference is the problem, and find the channels that minimize it.

Phew, it's been a long time since I've compiled a unix tar. I'd need a whole other computer to run this and sit there collecting data, correct?

Dave

If packet loss/delay statistics would be useful and you can forward pings to an always-on wireless device, set up a f8lure ping graph:

That might identify transient interference issues - i.e. you could see that there was a lot of loss/delays whenever DECT 'phones were used.

If you can't forward pings, it might still be useful to see whether the internet-connected device itself is having the issues rather than the wireless.

Found this. No personal experiance may help may not.

" snipped-for-privacy@gmail.com" hath wroth:

Nope. What you need is a "LiveCD". It boots Linux and runs Kismet. My favorite is:

Be sure that the wireless device in the monitor PC is supports. You can do remote control of sorts with VNC.

However, I think you're wasting your time trying to setup a remote monitoring station. Kismet will show much more than the typical Windoze wireless sniffer (Netstumbler) because it will show access points that hide their SSID and client radios. That's fine if you expect interference from wi-fi networks, but useless for non-802.11 sources. See list at:

Kismet can be operated remotely as resident inside a WRT54G type wireless router. No computah required. See "Kismet Drone" or "Kismet Server":

There are several ways to install, configure, and operate a remote monitor, so please RTFM before attacking. I have several of these installed (monitoring convention hall usage). However, they are useless for non-802.11 interference sources.

You might have better luck with a spectrum analyzer. I use several including the original version of WiSpy:

I've never tried to operate it by remote control.

The problem here is that the original version is rather deaf and can't really pickup weak sources of interference. For that, you'll need either the current model, or a real HP or Tektronix spectrum analyzer. The cheapest I've found that's usable is a Tektronix 492 which typically goes for about $1,500.

I'm not sure what to suggest. It's difficult enough to find an interference source in person. Doing it by remote control might be impossible. I've never tried it. What I usually end up doing is borrowing a spectrum analyzer, connecting it to the most directional antenna I can find (i.e. grid dish), and play transmitter hunt. Even that's not guaranteed.

My most effective indoor method is just a laptop and ping. I run continuous ping to the access point and walk around. As I get closer and closer to the source of interference, the latency and packet loss both increase. Sitting the laptop next to an operational 2.4GHz cordless phone usually drops the connection. (Note: interference can enter at both the client and the access point ends of a wireless link).

Other methods are to simply monitor the interference and look for a pattern. I had one problem that would only appear erratically at around lunch time. At lunchtime, the entire building wireless network would completely die. After lunch, it would recover. After 3 months of head scratching, someone else traced it to the worlds most leaky (and filthy) microwave oven on the noontime lunch truck.

Good luck.

Would a zap checker plus filter work for finding the interference source? I've seen wifi cavity filters for $100 plus change.

have the original zapchecker that was being sold as the product line was being developed. There are mods to add a SMA to the box. Of course, this is not a remote solution, but more of a curiosity for me.

snipped-for-privacy@sushi.com hath wroth:

They have several models. One of them claims at:

"Standard 2.4 GHz wireless telephones and microwave ovens make excellent signal sources. Using an operating sealed microwave oven, it is common to detect the oven?s 2.4 GHz signal using the Zap Checker products at greater than 10 meters distance. The Zap Checker Model 300 and ABC 126 with directional Yagi antennas can detect wireless 2.4 GHz telephones (10 mw of power) at distances greater than 60 meters."

I played with what I think was the original model with the internal PCB antenna. It would detect my Wi-Fi access point, but only if I was moving continuous traffic. When the average transmit duty cycle was low, it didn't do so well. However, the problem I found is that it was so sensitive, that ANY nearby RF source would indicate on the meter. We have a nearby VHF water district remote base. When it transmits, that's all I could see. If I were anywhere near broadcast AM/FM/TV transmitters, that's all I would probably see. Without frequency selectivity, such broadband devices are not very useful.

Yech. Build your own. A PCB with one of the ceramic BPF filters found all over wi-fi hardware should be sufficient. If you want lower loss, a simple cavity resonantor is easy enough to build. There should be something in the various ARRL microwave books. A narrow band 2.4GHz antenna will also help.

So, try it. Play T-hunt. Have someone hide a beaconing access point in your house or office. You get to play transmitter hunt and find it. Extra credit if you have other wireless access points and clients in the area creating havoc and confusion. I've actually done this using a keychain wi-fi finder and reflector, with predictably dismal results. Bottom line is that if you can't distinguish the desired xmitter, and can't seperate it from the others, you'll have big problems.

Well, rolling my own cavity filter would give me an excuse to get the RF generator fixed. I have a RF power meter, so that should be all that is needed to tune one.

The DIY cavity filter would be a good geek merit badge. I'll look into it. Much like building the biquad wifi antenna, I suspect it is not cost effective unless you count the knowledged learned in the process.