4000mW WiFi Rifle

Details

WARNING! Lots of terms, and jargons used! Exercise due research, Google is your friend! Also, I just started learning about this, so I may need citation in some parts. Kindly post a comment so I can update the writeup if necessary ;-)

Intro

The WiFi Sniper is a device that I put together based on a project I saw on Hackaday.com. The use case for this device is trivial, and somewhat illegal. This may also pose some health issues due to the concentration of the signal, and excessive amounts of radiation transmitted by this device as specified in OET 65. Prolonged use is not recommended.

The WiFi Sniper does not only look menacing, but it actually performs as good as it looks. Similar to Sniper Rifles, the WiFi Sniper has a 6x24 sniper scope for precisely pointing the antenna at an access point. A 2000mW ALFA AWUS036NH WiFi card, and a 4000mW WiFi amplifier drives the modified 25dBi Yagi-Uda antenna. This computes to 25dBi + 36dBm (4000mW) = 61dBm EIRP which is above the legal EIRP limit for commercial use of around 30dBm (1000mW) in most states, and around the world.

To demonstrate how powerful this device really is, it is unable to detect access points that are up to 10 yards away as it drowns out the signals sent out by the access point when directly pointing the antenna to it. I was only able to detect my access point by temporarily blocking the antenna with my body, and reads out 100% RSSI (Received Signal Strength Indicator) at -1dB. In addition, it detects access points approximately 30 yards away (through a wall or two and a couple of steel fences), and still be at least 70% to 80% RSSI and somewhere between -24dB to -36dB!

Components

1 × 15-element 25dBi Yagi-Uda WiFi Antenna

1 × Active WiFi Amplifier I'm using a 4000mW amplifier from Edup.

1 × Alfa AWUS036NH USB WiFi adapter

1 × Pigtail Male SMA to Male RP-SMA connector for connecting the WiFi card to the Amplifier, this should be supplied with the amplifier.

1 × DC-DC Step-Up Converter Variable output up to 35 volts, at 2.5 Amp max output.

Project Logs

Collapse

Any other uses?

TacticalNinja • 11/01/2016 at 15:38 • 0 comments

Okay, so some of you may ask "what other things is this good for"? At the heart of this project is a 2.4GHz amplifier that increases the output power, and is also spec'd to increase gain by a few dB. This is not exclusive for use with WiFi, we can use any 2.4GHz source and it will still amplify the transmit power. This is not very useful for Bluetooth and WiFi, since these radio protocols require both ends to have good signal both ways. One use case is to have a radio that can still function one-way. NRF20L01 is a 2.4GHz transceiver, which is very cheap BTW, and does not have a radio protocol similar to BT or WiFi. It is able to send raw data from a micro-controller or computer. Similar to shooting at someone with a gun, you don't necessarily need a confirmation from that person by asking if he's shot. If you can see them go down, or get hit you have visual/audible confirmation that contact has been made. Similar to this is radio control; if the receiver can receive your commands, it does not necessarily need to send back telemetry data to be able to do process the command you sent. It only needs to do a checksum on the receiving side to confirm on itself that it has received the correct and complete command.

Sadly, shipping from China is very slow, and I'm currently stuck until parts have arrived, but we can see where this project is going.

Power Supply

TacticalNinja • 10/18/2016 at 00:26 • 0 comments

So I decided to make the battery pack a bit more permanent for now by mounting it on a perf board. I'm still waiting for the other charging circuit, and DC converter which is more compact and better than the one I'm using now.

Wood Stock

TacticalNinja • 10/14/2016 at 11:11 • 0 comments

I was finally able to actually attach the thing to a proper stock. It took me quite a while since I don't have the right tools.

Build Instructions

Collapse

1

Step 1

Fixes
I bought a sketchy 25dBi Yagi-Uda antenna from China which did not perform great out-of-the-box. It had a hard time detecting access points just a few meters away, and my 5dBi Dipole antenna outperformed it in every way (even the range!). I did a bit of reading to learn about how the Yagi-Uda antenna works, and what I should expect from it. I noticed quite a few things from the one I got: It had a 2m coax cable, a "Balun", a misaligned driven element, and a screw that was too long, which causes the driven element to ground with the boom and parasitic elements. The first fix was to reduce the length of the coax cable from 2m to 15cm (about 6 inches), because even low-loss coax cables can reduce the received signals by as much as -10dB. Second was to open up the plastic case from where the driven element of the Yagi is mounted to check for sketchy soldering connections. From there I noticed that it had a "Balun", which is a wire extention connected with the driven element, to "Stabilize" the received signals. However, for UHF antennas (such as WiFi antennas, which are 2.4GHz and 5GHz) this is unnecessary, and may even introduce unnecessary loss in signal strength if done incorrectly; so I removed it. Third was to fix the misaligned driven element as it was a couple centimeters off the center of the folded dipole. I only needed to rotate its axis on the antenna's boom. Finally, I snipped the screw to make it a few millimeters shorter.
I should have tested each fix to see which of those affected the poor performance overall, but all of the fixes ended up making this cheap Chinese Yagi-Uda antenna to be an effective one. It is now able to pick up more access points at a greater range. Basically, it's working how it's supposed to.
2

Step 2

Power Supply
Making the portable power supply consisted of an adjustable DC-DC step-up converter, a Li-poly Cell, and a micro USB Li-ion charger. I had to cut the JST connector off off the Li-poly cell since the charger I got didn't have a JST connector. The step-up converter is wired in series with a slide switch, then the li-poly and charger are wired in parallel to the converter.
3

Step 3

Future Upgrades
I'm thinking about using a cheap airsoft's plastic body instead of making one out of wood, but I really like the weight and sturdiness, and look of a wooden stock. Ruining a good airsoft may also cost more. I would get a better Li-ion charger with an onboard switch, JST connector, and proper output pins to connect the DC step-up converter to. I also plan on using a single-board computer (*cough* Raspberry Pi *cough*) to do all the processing.

View all 3 instructions

Discussions

ActualDragon wrote 10/14/2016 at 13:59

so what do u use it for?

Are you sure? yes | no

TacticalNinja wrote 10/14/2016 at 17:33

Well, given that it's illegal and all, theres also a health risk involved. I probably won't be using it for anything practical. The obvious uses are for long range wifi hacking and recon.

Are you sure? yes | no

george wrote 10/14/2016 at 17:49

What kind of health risks are involved? How far out of FCC spec is it?

Are you sure? yes | no

TacticalNinja wrote 10/14/2016 at 18:01

It's about 31dBm EIRP above the FCC specs for consumer grade WiFi. The signal strength doubles for every 3dBm increase, so do the math. Exposure to strong radiowaves can damage cells, and may cause cancer. I'm no expert so I could be wrong.

Are you sure? yes | no

ActualDragon wrote 10/16/2016 at 20:29

so would it turn off the wifi or could you use it for like, really hacking hacking

Are you sure? yes | no

TacticalNinja wrote 10/17/2016 at 00:10

Well it's not like a microwave transmitter that fries electronics. Think of it as a really strong WiFi adapter.

Are you sure? yes | no

mountainsof wrote 10/14/2016 at 13:43

Have you tested to find the "field of view" for that antenna?

Are you sure? yes | no

TacticalNinja wrote 10/14/2016 at 17:42

I imagine it would be hard to do that. No specs sheet can be found for these Chinese knock-offs, or atleast nowhere is it specified how many degrees the beam spreads out to. A really rough estimate would be within 20-10 degrees.

Are you sure? yes | no

4000mW WiFi Rifle

Details

Components