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HackRF - Help with 2.4 GHz Signal Registration


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I am trying to analyze the signal that is going

    from a 2.4 Ghz RF remote control

    into the TV that has a USB port with a dongle connected

I could find the frequency and could see in in SDR#


but the signal is too weak, even if I hold the remote next to HackRF's anthenna, and sometimes it does not register the signal at all. The TV is 4 steps away and registers the signal every time.

the remote has Beken BK2535 DH650QS chip in it:



What am I doing wrong? Is there some setting that needs to be adjusted?

Thanks a lot!





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First off, I would find the FCC Registration ID number for the remote.  You have to look for that on the remote itself, perhaps there is raised lettering on the unit or a sticker somewhere, may even be inside the battery holder. Then, Google that registration number to find it in the FCC's database, go through the data to find the transmit frequency and the type of transmission such as OOK (On/Off keying). The transmission type will give you some idea of how it will appear on a waterfall. 

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You may also want to do your testing away from other 2.4 GHz sources.  If there is an overlaying transmission from another source it could be "washing out" the TX you are trying to analyze.

Do you have a brand or model of the device you are analyzing?  More information would help in finding possibly the frequency, modulation type, mode of operation.

Depending on devices you can actually have a transmitting device to close to the receiver were there can be a dead zone of the antennas  This is however unlikely with such low powered devices being used. 

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I have 3 remotes/devices that work on 2.4Ghz frequency with dongles and I have hard time registering signals with HackRF on all of them.

Here is one example (not the one in the first posting):

Measy RC12 remote control with keyboard and air mouse.



Frequency: : 2402-2480MHz   
Modulation : FSK    
Number of Channel  :  157 Channels 
Frequency Separation  :  0.5MHz   
Antenna Type  :  Integral   
Antenna Gain  :  0 dBi 

any idea how to make HackRF registering a strong signal for that?



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You might want to do some research on using the HackRF for Bluetooth.  There can be some issues and things that need to be modified for it to work with Bluetooth, is my understanding of it.  A device like Ubertooth One is more suited for use with Bluetooth out of the box.  

May want to give this a read: https://www.reddit.com/r/sdr/comments/48db0a/sniffing_bluetooth_with_hackrf/    The article describes some of your problems you mention about signal strength as well as other issues.


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I think I have got some clues. Ubertooth One would be a nice thing to have, but it costs quite a bit (in addition to HackRF that I already have). 

I think I will try NRF24LU1 to start with. Maybe it will catch the signal differently. Those RF dongles that receive the signal from the remote control are really small to be able to do many manipulations, and they all work really good. Very rarely happens that a press of the button will not go through. So, there must be something that could filter out most of the noise. would that be the exact frequency, sending sync on several channels. i guess I will have to figure that out. 

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