How do I pinpoint a wifi source?

[T_Warne]

I live on 80 acres of rolling hilly forested land and my nearest neighbor is beyond a rise ( not line of sight ) over 1/2 mile away. My property is surrounded on all sides by cultivated fields of wheat and hay. There is a road along one edge of my property which would allow easy access to my land, although the entire stretch is posted "NO TRESPASSING" as per local regulations.

Since the beginning of hunting season I have noticed odd wifi signals popping up and have a sneaking suspicion that it is hunters using wifi game cameras to scout my property. As a matter of fact, a new one popped up this afternoon.

I would like to pinpoint these wifi sources to be sure that it is not someone illegally hunting on my property. Is there an easier way than wandering around the forest with my cell phone watching signal strength?

 

[Sigurthr]

What you need is called "direction finding" and is a sort of "sport" amongst amateur radio operations. Unfortunately, it isn't the most straightforward task. You need a receiver for the radio frequency and mode(s) of the transmitters you're looking for, and you need a specialized antenna system that has one side that almost totally blocks reception. You then scan around using various techniques to determine which facing has the lowest signal reception, and you know that the source is a straight line from the side of the antenna that blocks signals.

 

[T_Warne]

Thanks for the reply. Is this something a guy with no radio knowledge can do easily? Is the equipment expensive? Where could I buy a detector or kit set up for wifi?

 

[crazyspaz]

Dang, that's pretty crappy. If you do find them (which I hope you can), make sure to leave them and file a report with the necessary authorities. Trespassing isn't legal as it is, but I would imagine trespassing+hunting would be a whole different thing.

 

[Sigurthr]

replied to PM =).

short and sweet; make a directional 2.4g antenna using an old sat dish.



*RF guys; yes the receiver won't be at the optimal place and the radius won't be right because the freq difference and it will likely not even be near a wavelength node, but the shielding effect should provide -some- directionality.

 

[Alaskan]

Expense might be too much, but here's a small spectrum analyzer with LCD display you could use if hooked up with a directional antenna:

Pocket RF Explorer Handheld Digital Spectrum Analyzer Analyser 2 4G Hi Quality | eBay

Wifi beam antenna: High Gain 16dBi WiFi Booster 2 4GHz Yagi Antenna RP SMA New for Router Modem 5M | eBay

The antenna uses a reverse polarity connector, here's an adapter to convert to standard SMA: Adapter 90° RP SMA Female Plug TO SMA Male Plug RF Connector Right Angle M F | eBay

 

[T_Warne]

@Alaskan (aka Laser Project): That is totally in my price range. Will it actually do what I need?

 

[Sigurthr]

A directional antenna (yagi or parabolic) for the band you are interested in (2.4GHz) plus a low loss feedline for that band, and a sensitive spectrum analyzer that covers that band is what you need, yes. Whether or not the ebay one linked is any good... I cannot say.

 

[Alaskan]

I don't know if the ebay model I linked to is any good either, but something like that is what I'd buy if I were to go transmitter hunting.

 

[T_Warne]

If you had a budget of around $250 what equipment would you buy?

Thanks guys. I really appreciate your input.

 

[Hemlock_Mike]

Long ago in ham radio, we would put a radio or just the antenna in a
metal trash can. That was at 144 Mhz but it worked pretty good at
distance.
HMike

 

[Blarg King]

This seems to be an out-of-the-box solution to your problem. Unfortunately the kit that includes a directional antenna costs over 1000$.

Wi-Spy Professional Spectrum Analysis by MetaGeek, makers of inSSIDer | MetaGeek

 

[Alaskan]

Have an iPhone? There used to be a Wifi radar app which was kinda cool, you could see relative signal strengths of WIFI signals with that, the post about using a garbage can lid to block the signal as a method of direction finding might just work.

 

[T_Warne]

@blarg king That would be perfect, except for the cost. I've bookmarked it just in case.

 

[Alaskan]

This is really cool, did about 20 minutes of googling to find it: (Edit: Nevermind, price too high, just found they don't sell the single WiFi spectrum analyzer module anymore).

iPad Spectrum Analyzer for 2.4GHz ISM Band | Electronics and Electrical Engineering Design News | EEWeb Community

 

[Dr_Evil]

This is pricey but something like this might help you pinpoint the signal location once you know the general area it is in.

KJB Security Products DD1206 RF Wireless Signal Detector DD1206