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QUICK SPIDER - No Soldering, No Connector

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  • #31
    It doesn't matter the cable RG6 is 75 ohm?


    • #32
      Originally posted by apeiron69 View Post
      It doesn't matter the cable RG6 is 75 ohm?

      No, it does not make any difference as the DVB-T dongle has input impedance of 75 ohms. The DVB-T is designed for TV reception, and the TV system uses 75 ohm.

      Even if the dongle was 50 ohms, in receiving situation like we are, the mismatch between 50 and 75 ohms does not cause an appreciable loss in performance (the SWR for 50 to 75 transition is 1.5, and mismatch loss is only 0.177 dB). As in receiving scenario, the power levels are in milli or even micro watts, which are easily compensated by front end circuits of the dongle.

      For transmitting equipment the 50 to 75 ohm mismatch should be avoided to reduce reflected power, as the power levels involved are in watts or tens of watts or even hundreds of watts.
      Last edited by abcd567; 2020-06-15, 14:48.


      • #33
        QuickSpider Ver2

        Part -1: Design

        Designed By Computer Simulation


        V-Spider 84-45-141-SWR.png




        • #34
          QuickSpider Ver2

          Part -2: Building & Testing of Prototype

          Comparison of V-Stub QuickSpider with Bench Mark Antenna (Flightaware Antenna)

          FA Antenna >> 30cm RG316 pigtail >> FA light Blue Filter >> FA ProStickPlus (blue) >> OrangePiPC
          V-Stub Antenna >> 100cm RG174 pigtail >> Radarbox24 FlightStick (green) >> RPi4

          Flightaware 26" Antenna on left side of window
          V-Stub Quick Spider on right side of window
          Horizontal spacing between antennas = 30 cm

          NOTE: The paper behind V-Stub was placed while taking snapshot, as without it the thin wire of V-Stub was not clearly visible in the photo.

          V-Stub with FA.jpg

          Pilot Antenna's Dimensions & SWR

          V-Spider-Pilot-Built and SWR-3.png

          Comparison: Number of Aircrafts Tracked


          Comparison: Message Rate


          Comparison: Maximum Range


          Last edited by abcd567; 2020-10-17, 19:53.


          • #35
            V-Stub on Mag-mount Base (placed on a metallic plate)

            V-stub wire collinear-35pc-E2.jpg


            • #36
              I've made e version of this antenna a couple years ago, it has been outside at least 2 years feeding fr24 24/7.
              Performance has been dropping lately and I discovered corrosion in the connector, decided to make a new version similar to my old one.

              I bought a VNA called nanoVNA V2 and wanted to be able to test and tune my new "quick spider" antenna. I got some readings, but for me with my limited radio technology knowledge I find them almost to good to be true or did I get lucky? I did cut a little bit off the center wire two times to tune it, but that's it.
              I have calibrated the nanoVNA for the short frequency band 900-1150 mhz as shown in the screenshot, antenna coax lenght is about 2-3 meters.
              Antenna is made of RG6 coax and spider is weather sealed with epoxy.


              Any comments to the screenshot above would be appreciated.

              Attached Files


              • #37
                Originally posted by kredittkort View Post

                Any comments to the screenshot above would be appreciated.


                Last edited by abcd567; 2020-11-03, 18:09.