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  • Do I need a LNA?

    Hi

    I enjoy trying to improve my setup with minimal outlay. With this in mind I forked out a whole 4.37 on one of these https://www.ebay.co.uk/itm/1-Pcs-ADS...-/293041458452 What did I have to lose?

    As it turned out I had a lot to gain; about 50-60NM (130ishNM to a constant 190NM), once I lowered the gain on my dongle from AGC to 40.2

    Anyhow, during the storm Ciara that struck the UK on Sunday, we lost power several times and when it was all over I discovered that filter/LNA was dead. I had been powering it from the Pi 5V header and am guessing a spike did for it?

    From this event, I am assuming that this is a delicate device and rather than try again with another, I am wondering if I should just buy myself a passive filter. I have attached a section of the scan of RF signals plotted by rtl-power (having followed an excellent article by ab cd, on the planefinder forum).

    My question is to canvas opinion as to whether the integrated LNA on this device contributed in any way to my improvement in detection, or whether it was all down to the filtering out of nearby nasties and the LNA just counteracted the insertion loss, as suggested by the designer?

    If the thought is that filtering alone is likely the cause of the improvement are there any recommendations for a dirt-cheap (but worth having) ads-b filter that I might try?

    BTW the dongle I am using is a RTL-SDR Blog V3

    Cheers

    950.JPG

    1090.JPG
    Attached Files

  • #2
    You have strong GSM900 cell/mobile signal. You need a FILTER

    Filter alone (Flightaware 1090 only, dark blue) - 16.99 :
    https://thepihut.com/products/flight...ass-sma-filter


    Flightaware_Filter_1090_0nly.jpg



    RTL-SDR Triple Filtered LNA - USD $26.95 = 20.79 :


    https://www.rtl-sdr.com/product/rtl-...s-tee-powered/


    RTLBlog_Triple_Filter_LNA.jpg
    .
    Last edited by abcd567; 2020-02-13, 17:31.

    Comment


    • #3
      Originally posted by ThePhoenix View Post
      have attached a section of the scan of RF signals plotted by rtl-power (having followed an excellent article by ab cd, on the planefinder forum).
      I have posted this article in Flightradar24 forum and several other forums also:

      Flightradar24 forum: Do I need a Filter? - Find RF Signals In Area

      Planefinder forum: Do I Need A Filter?

      Flightaware forum: Do I Need A Filter?

      Radarspotters forum: Do I need A Filter?

      RadarBox24 forum: Do I Need A Filter?

      Radarspotters Team forum (Russian): Нужен ли мне фильтр?*(Do I Need a Filter?)


      .

      Comment


      • #4
        Thank you abcd567 for the swift response and the recommendations. I was in little doubt that I needed a filter, but was really wondering if any of the improvement I was getting was down to the integrated LNA.

        As the difference between the two options you have given is only 4 I think I should just go with the amplified choice. It will be interesting to see what difference I get between this and the sub 5 device that I was using.

        A couple of further things, if I may:
        • The "processor" is a Pi being powered by a 2A PSU. One USB port is running a WiFi dongle. In the other USB port is the RTL dongle. Am I likely to be fine T-powering the LNA/filter you recommend without any further modification/kit. I.e. just plugging it on the input of the RTL dongle and enabling T-power?
        • Secondly, is the best positioning of this LNA/fillet combination up against the input to the RTL dongle, or is it beneficial to locate it closer to the antenna?
        ​​​​​​Cheers

        Comment


        • #5
          Although it is preferable to install the LNA as close to antenna as possible, but is not an absolute requirement, and the LNA can be connected directly to the dongle, or placed somewhere in the middle of the coax. Installing LNA near an outdoor antenna will require to house the LNA in a weather proof box.

          Yes, with V3 dongle, you do not need any bias-t as the V3 has built-in bias-t to power the LNA. Simply connect LNA berween antenna and dongle, and enable bias-t power from V3 dongle by software (method given on their site).

          Take care to connect "OUT +5v" terminal to the V3 dongle and "IN" terminal to the antenna.

          Both of your questions are answered under "Description" on the page I have linked in my last post. I quote it below for quick reference.

          NOTE:
          The 2A PSU may not be enough to power RPi+V3 Dongle+LNA, and a 2.5A PSU may be required. As you already have a 2A psu, try it first, and if you note any troubles, replace it by 2.5A psu or higher.

          Description
          This is a high performance filter and LNA combination for 1090 MHz ADS-B reception. Designed to be used with bias tee power from our RTL-SDR Blog V3 dongles with the LNA mounted as close to the antenna as possible.
          Last edited by abcd567; 2020-02-13, 15:15.

          Comment


          • #6
            I didn't wish for you to go doing my research for me and was only asking as I thought they would be things that you may already know the answers to.

            In any case I am very grateful of the comprehensive advice.

            Thank you for taking the time.

            Comment


            • #7
              Originally posted by ThePhoenix View Post
              I didn't wish for you to go doing my research for me and was only asking as I thought they would be things that you may already know the answers to.
              I did not do any research for you.
              All the answers and information I have posted are things which I already knew.

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