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Filter position?

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  • Filter position?


    I've just bought a passive 1090 in-line filer for my basic Rpi setup but was wondering where in the chain is best to put it, near the antenna or the usb stick?

    Any advice would be great thanks.

  • #2
    Shouldn't matter, typically you use it near the receiver.

    If it was an LNA you would try to place it near the antenna but many people just place it near the receiver because that's where all the gear is.
    (With long runs of cable the LNA near the antenna can improve things quite a bit though)


    • #3
      That's great thank you.


      • #4
        I want to buy filer, but don't know if it will improve the receiption( I am living in big city). Please, share your experience.


        • #5
          Well to be honest I though one would help however my hits have dropped, I'm not certain whether I've done something or the filter isn't any good but I'm getting somewhere between 100-200 less hits a day. I'm going to try a few things for a week to see what brings better results in the end.


          • #6
            To determine if you need a filter, conduct a scan as detailed in this post:

            Do I need a Filter? - Find RF Signals In Area



            • #7
              This is all the filtering you need:

              It's an excellent device in my experience.
              Needs a bias-t to supply it with power though.

              Especially with home built antennas with low gain the above LNA is very beneficial.
              The LNA in the Flightaware Pro Stick Plus has the problem that it's easily overloaded by mobile phone signals.
              The rtl-sdr external LNA doesn't seem to have this problem and is very resilient against overloading by design.

              Even if the Flightaware passive filter helps reduce out of band signals, the signal itself is reduced quite a bit which reduces gain especially with homemade antennas.

              Anyway if you don't have a good view of the horizon your reception will be limited by geometry:
              Last edited by wiedehopf; 2019-05-27, 13:39.


              • #8
                If I understand correctly, it will help reduce noise from other frequencies and will help to improve receiption. Am I right?


                • #9

                  The closer to the antenna you use it, the better.
                  It's not waterproof though, so you would need to install it indoor or in a waterproof box or something of the sort.

                  You'll have to reduce gain significantly because it amplifies the signal.


                  • #10
                    Do I need to somehow configure this device or can I use it immediately after installation? Are there some more detail guides about it?


                    • #11
                      You should understand what a bias-t is. Maybe google it to understand what it does?

                      If you have an rtl-sdr v3 you can activate the internal bias-t.

                      Otherwise you need an external bias-t and feed that with 4 to 5 V.
                      (For example:


                      • #12
                        I have an RTL-SDR V3, so I can buy 1090 MHZ ADS-B LNA, activate the internal bias-t and have lower noises and better receiption, yes?


                        • #13
                          Yes that will work.


                          • #14
                            There have been some problems getting this stuff to work, blacklisting some various kernel drivers for dvb-t should fix any problems.
                            You can already do that right now then you won't forget it when you have the LNA:

                            echo -e 'blacklist rtl2832\nblacklist dvb_usb_rtl28xxu\nblacklist rtl8192cu\nblacklist rtl8xxxu\n' > /etc/modprobe.d/blacklist-rtl-sdr.conf