Designing a WiFi signal detector

[Peter222]

Hi, i want to build a Wifi detector (for detecting hiden Wifi connected NAS drives)

I think i have a good idea of what to do but would like some guidance.

I know thats its basically a RF signal at a frequency of around 2.4GHz or around 5GHz so i will need,

1.Recieving antenna. directional? or several antennas? patch antenna?

2.AD Analogue to Digital converter (unsure on interferance from other wifi signals, possibly it wont matter as only locating the nearest therefor strongest signal subsequently when that WiFi drive is found it can be swithced off and the next nearest located) Possibility of decoding which signal is wich and selecting the one you would like to trace. (i think this would be to complicated but would like to know the theory of how that would work)

3.DSP Filter with a pass band at 2.4GHz and 5GHz with a sampling frequency of at least 4.8GHz AND 10GHz respectivly, unsure on order at the minute.

4.Measure amplitude (possibly bridge circuit)

5. Output if one antenna is used then just a simple barchart LED strength indecator or several antennas so can determine an angle between each and therefor 'point' in direction of strongest signal?

Im aware of the keyring WiFi detectors (ive bought one but it is yet to arrive) im assuming they are quite simple as they're cheap so i intend to open it up to see if i can understand how it works.

I do appologize if there are posts on here that all ready cover some of this but i am reading throught them at the minute.


Any help at all would but greatly appreciated!

 

[biff44]

So you are going to use an ADC with a 10 GHz clock to do a wifi signal generator? Good luck!

 

[gbmhunter]

Similar to the keyring Wi-Fi detectors are the t-shirt based ones that light up when there is a Wi-Fi network nearby. Pulling apart either may be a good place to start.

 

[bigdogguru]

Why reinvent the wheel? Why not use one of the readily available WiFi USBs couple with a small embedded linux device to process the WiFi USBs output. The software, WiFi and Linux device already exist.

 

[Peter222]

So you are going to use an ADC with a 10 GHz clock to do a wifi signal generator? Good luck!

Im not sure if i follow? I just need to build a signal strength indicator for a 2.4GHz RF frequency Is this the wrong way to do it?


I have orderd one of the key ring Wi-Fi testers that should be here tomorrow. So i can dismantle and inspect that.

Basicaly i would like to understand how these Wi-Fi strength meters work, they can't be to complex as they are so small in size.

I'm looking into the Linux howeve that would need to be coupled with a laptop or pc which is too complex for what i want.


Does anybody know how these small keychain devices work?

 

[Audioguru]

Why are you going to make a microwave oven radiation detector that will also detect every 2.4GHz wireless phone and 2.4GHz RC model airplane nearby?

 

[Peter222]

Why are you going to make a microwave oven radiation detector that will also detect every 2.4GHz wireless phone and 2.4GHz RC model airplane nearby?

Well thats not my intention, i solely want to detect Wi-Fi signal coming from a hidden Wi-Fi NAS hard drive. Its a project aimed around the ideas of people using hidden storage devices and accessing them remotely. This is currently a problem for the Police service, trying to find these 'hidden' devices.

My keychain detector has now arrived so i'll dissmantle that in the hope of understanding how it works.

Any useful input would be much appreciated

 

[Peter222]

wow not one person has any idea :shock:

Even if someone knows the theory of how to distinguish between Wi-Fi and other RF frequencies that would be a start!

 

[medaziz]

Hi to all

good work

but to distinguish between Wifi and other RF frequencies we should simly using the 2.4 or the 5 GHz it's a normalisation.

 

[Audioguru]

Thousands of products and microwave ovens use 2.4GHz.
But 2.4GHz has many channels so that interference is unlikely.