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Return to BlogSimple No-Tune Wi-Fi Sniffer
Posted Jan 14, 2012 at 2:40 pm
Figure 1
Here is a circuit of a very basic No-Tune Wi-Fi Sniffer. It’s about as simple as it gets, using only two transistors. It could detect my notebook at 10 feet with a tiny vertical. No doubt, a Well Tuned Dipole would increase it’s range.
Q1+Q2 are RF amplifier stages tuned to receive 2.4 – 2.5 GHz. L1+L2 are molded chokes. The critical components are L1, C3, L2 and C6.
LED1 is the signal indicator. As you approach a signal source, the LED [1.3v], will become brighter. It’s most useful in dim to dark areas, this is due to lack of current, however, there are now more efficient LED’s available, so it may be useful during full daylight. Alternatively, you could use an old VU, or MA DC meter instead of a diode.
The needle will gradually rise as you approach the signal source. 50K potentiometer should be placed across the meter and adjusted near a Wi-Fi for Full Scale. The sniffer should be built into a metal box to minimize hand capacitance and stray RF effects.
For the imaginative, a Low Current DC Buzzer could be used.
Be aware that most strong RF signals can produce a reading. Harmonics from mobiles, portables, CB’s, microwave ovens, and even mobile phones, or their towers are among the most common causes. Either way, it will indicate weather it’s worth while or not to open your notebook and check out a signal.
Designer & Author: Special thanks to Laszlo Kirschner.
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3 years ago: Hi, I am trying to built the circuit. However, I couldn't find L1 : 1nH, L2 : 2.2nH.The smallest value of inductor that I can find is in Mili unit. Can you suggest any other component to replace them?
3 years ago: Hello there I am a newb to this. But I was wondering if someone knows how to build/buy a circuit that recieves a signal over a WiFi network that could ultimately triger another circuit, like a motor unit for example. So basically a signal sent from a device (i.e. Mobile phone) then recieved by the circuit then another circuit gets trigered upon command. I thank you so much in advanced for your help.
Regards,
Bill M.S.
3 years ago: bill m.s did u find a circuit i'm looking to exactly the same thing. maybe we could join forces.
2 years ago: Hi Bill, I hope you're not trying to build a bomb hehe! Just kidding. Normally some cellphones are used to trigger an explosive device once it recieves a call or a ring.
2 years ago: Hey! Does anyone have a list of the equivalent components for thru-hole? It would be easier to test the circuit. Thanks!
2 years ago: I guess if I add more power to this device, I can increase the range that it can reach without replacing the antenna...
2 years ago: this is cool! it's like roaming around the moon and looking for signals :)
12 months ago: Hey there , was wondering if you could generously provide info on which part is bought from which manufacturer, would help a lot.