Fighting RFM 69 NACK's



  • Once a week I was having NACK blackout. All nodes could not send nor receive anything. Initially I was resetting everything and after some 20 minutes I was “able to fix” things. However, it was reappearing. Looked very strange. I bought very very very useful device called RTL-SDR (R820T) software digital receiver. Just in case you do not have, it is worth to buy. Yes, it is around $7 dollars from aliexpress include delivery. The device is not good for NRF since range is 24 - 1766 MgHz but for RFM it is super good. Back to my problem though, I found the noise at 429 -437 Mghz and it lasts around 20 minutes, the time “I was fixing things” previously. Huh!
    Video
    https://youtu.be/BH_hDyWGr5I
    You can see from the video, blackout was at the frequencies from 429 -437 Mghz
    After that, I switched RFM 69 to 440 Mghz and see results. 5 transmissions!!!
    https://youtu.be/jlE2p07-jOY
    The device is super useful toy!!! You can listen FM radio and other air traffic control towers.
    Found later is not legal to use 440 Mghz though…
    The RTL-SDR (R820T):
    With this tutorial you can turn RTL-SDR (R820T) into 24 - 1766 MgHz receiver and see what happens in the air.
    http://www.rtl-sdr.com/rtl-sdr-quick-start-guide/

    0_1495314594386_P_20170520_210119(1).jpg
    Hope it is helpful.


  • Contest Winner

    It is also possible to use this superior tool to find possible influences with other RF devices 😉


  • Mod

    Interesting results, and great use of RTL-SDR.

    Seems like there is a lot of activity on the 433 band. Do you have any idea what it could be? Wireless headphones/speakers or a baby monitor perhaps?



  • @mfalkvidd said in Fighting RFM 69 NACK's:

    like there is a lot of activity on the 433 band. Do you have any idea

    really no clue. it is started like this (different zoom):
    0_1495316193107_nooiseStart.jpg


  • Contest Winner

    @mfalkvidd Personally I am sure it is a jammer. But I do not know it is a professional jammer of secret services or an amateur device.


  • Mod

    @Koresh that seems likely. I can't think of a legit way to use all those constant transmissions over the entire band. It certanly doesn't adhere to any duty cycle limitation.


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