Hi,
I would like to build a small handheld detector that would indicate the presence of a Bluetooth signal. It would be used at close range to identify if a specific person had a Bluetooth enabled phone or device turned on.
A quick internet search shows that these are available but they are anything but cheap.

Could this be as simple as strapping a few cheap modules together?
Any thoughts on this would be helpful as I have not looked into RF projects before.

 

Use a cellphone to detect the cellphone or Bluetooth device.
https://play.google.com/store/apps/details?id=com.bluetoothFinder

 

Use a cellphone to detect the cellphone or Bluetooth device.
https://play.google.com/store/apps/details?id=com.bluetoothFinder

Nice and easy for sure, but do you think that app would work with non-discoverable devices? I don't.

https://link.springer.com/content/pdf/10.1007/978-0-387-75462-8_20.pdf

 

Exactly.
If someone is trying to hide a device they would obviously turn its discovery mode off.

All I am interested in doing in detecting the transmitted signal, not any of the data contained in it. I think its 2402 to 2480 mhz.

 

https://play.google.com/store/apps/details?id=com.bluetoothFinder

It said it will find them if there on don't have to be set to discover

 

https://play.google.com/store/apps/details?id=com.bluetoothFinder

It said it will find them if there on don't have to be set to discover

@be80be Really? Where do you read that?

Here is the entire blurb that I see from the site:

"With this app you can locate and find your bluetooth devices using the received signal strength indication (rssi), the closer you get, the stronger the signal will be. DOES NOT WORK WITH HEADSET. The devices will be displayed in a list with their: name, MAC id and a graphical signal strength meter (S Meter), and units in decibels dBm. Depending on the device the signal strength could be updated on 1-10 seconds intervals.

This app is specially recomend by Fitbit users. There is a Pro version available without ads and new features as one device selection.

IMPORTANT NOTE: To work properly it is necessary to turn on the Bluetooth in discovery mode. PAIRED DEVICES AS HEADSETS WILL NOT BE FOUND.

Be constructive please , if this app does not work on your device, instead of negative rating, send me a email with the device model and problem description in order to solve it.

Thank you"

 

A SDR with 2.4GHz Mmds Lnb down converter should work to see the raw RF of any transmitter in that range.

https://www.amazon.com/RTL-SDR-Blog-RTL2832U-Software-Telescopic/dp/B011HVUEME

https://roks-tv.com/solutions/mmds
https://www.made-in-china.com/products-search/hot-china-products/Downconverter_Mmds_Lnb.html

https://hackaday.com/tag/lnb/

 

Raymond Genovese Just one thing have you tried it.

Be constructive please I'm sure you have not.

Just because I said it works looking for bluetooth by received signal strength indication (rssi)

The dam thing is looking for a signal not a discovery id That's what they say the
I have found bluetooth with the app I have and discovery is off.

 

be80be sorry I asked you. Especially after seeing your edits. I will leave it at that.

 

A SDR with 2.4GHz Mmds Lnb down converter should work to see the raw RF of any transmitter in that range.

Thanks spook for digging this up. Even though it looks a bit large to turn into a small handheld device,I might get some other ideas from it.

 

Use a cellphone to detect the cellphone or Bluetooth device.
https://play.google.com/store/apps/details?id=com.bluetoothFinder

Just to see how good this app would be ....... the test ran.........
I turned on my Airplay speaker and set Bluetooth to hidden. Also turned on a Sony Walkman and paired it with some headphones.
Ran the app on an Android Samsung Galaxy ..... it detected nothing at all.
I forgot, there was a Fitbit on the desk next to the phone and it did not see that also.


Fail comes to mind!

 

Just to see how good this app would be ....... the test ran.........
I turned on my Airplay speaker and set Bluetooth to hidden. Also turned on a Sony Walkman and paired it with some headphones.
Ran the app on an Android Samsung Galaxy ..... it detected nothing at all.
I forgot, there was a Fitbit on the desk next to the phone and it did not see that also.


Fail comes to mind!

If the device is not in discovery mode, you are not going to see it with a Bluetooth device. That is pretty much what the standard demands - if you are in discovery mode, you can be seen, if you are not in discovery mode, you can't be.... at least not by a Bluetooth standard device.

I would not expect that app or the Pro version to work at all for finding devices that are not in discovery mode - others can have their opinion but that is my opinion.

Don't be fooled by the the RSSI measures that you can see on those screens - that is relying on the TX power information which is included in the advertising packet...when it is in discovery mode. Bottom line, again, in my opinion, a device that is not in discovery mode is not going to show up on a simple app like that one or the Pro version.

Now, non-standard Bluetooth devices such as Bluetooth sniffers like this one http://ubertooth.sourceforge.net/hardware/one/ that is a different story and you can get MAC info from the packets and potentially identify a "secret" device, as it were. Not something I have ever done though and not something that looks particularly easy to me.

That's what I think anyways...for what it's worth.

 

Thanks spook for digging this up. Even though it looks a bit large to turn into a small handheld device,I might get some other ideas from it.

You could also get a https://github.com/mossmann/hackrf/wiki/HackRF-One

 

A couple more adds on the topic...

Previous thread https://forum.allaboutcircuits.com/threads/rf-detector-2-4ghz.139027/

Anti-cheating detector (don't know what that one costs) https://www.cleverintelligenceunity.tw/en/product-548489/Against-Cheating-on-Exams-
Anti-Spy-Bug-Detector-for-4G-3G-GSM-Wi-Fi-Bluetooth-RFD-16.html

Little hand-held RF detector (I wonder how well it works) https://www.brickhousesecurity.com/counter-surveillance/rf-signal-ii/

 

Nice and easy for sure, but do you think that app would work with non-discoverable devices? I don't.

spy camera

You can also use the different type of spy gadgets

 

You could also get a https://github.com/mossmann/hackrf/wiki/HackRF-One

best anserw