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  • CRITICAL DEPENDENCE OF ANTENNA TUNING/SWR ON COIL DIMENSIONS
    I was modelling a 4-element dipole with single-turn coil. I used two options
    (1) for countries using Imperial/US system: use 3/4 inch dia PVC pipe as former to wind the coil.
    (1) for countries using metric system: use 25mm dia PVC pipe as former to wind the coil.

    The 3/4 inch PVC pipe has outer dia = 1.05 inch = 26.7mm
    The 25mm PVC pipe has outer dia = 25mm
    The difference between two dimeters is about 6.5%. I did not expect any difference in design if any of the two coil inner diameters are used.
    When I ran the simulation, the outer limbs for lowest SWR were:
    (1) 192mm in case of 26.7mm dia coil (3/4 inch pipe as coil former)
    (2) 206mm in case of 25mm dia coil (25mm pipe as coil former)

    Above shows how the tuning of antenna and achieving low SWR is critically dependent on coil dimensions.

    Please see the screenshots of two simulations below.

    CASE 1 - Coil inner diameter = 26.7mm (Coil wound over 3/4 inch PVC Pipe)

    15018570360_9bdc5ebf86_o.png , 15018464829_0e3a161f6e_o.png




    CASE 2 - Coil inner diameter = 25mm (Coil wound over 25mm PVC Pipe)


    15202198921_a4701b6719_o.png . 15205248285_64835ef9ca_o.png
    .
    Last edited by abcd567; 2014-09-28, 08:48.

    Comment


    • Originally posted by abcd567 View Post
      Wow! 284 nm coverage!
      Can you please give some more details about your antenna, receiver, amplifier etc?
      Which software you have used to plot the range?
      Just for comparison here is my plot for today from my FR24 supplied box and antennae.
      image.jpgimage.jpg
      Ben.
      FR24 F-EGLF1, Blitzortung station 878, OGN Aldersht2, PilotAware PWAldersht, PlanePlotter M7.

      Comment


      • Originally posted by F-EGLF1 View Post
        Just for comparison here is my plot for today from my FR24 supplied box and antennae.
        [ATTACH=CONFIG]4719[/ATTACH][ATTACH=CONFIG]4721[/ATTACH]
        Ben.
        Mine one, almost 350 nm, near to overlap you being more than 1000 km apart.

        F-LEST1.jpg
        Northwest Spain: F-LECO1, F-LEST1

        Comment


        • Originally posted by F-EGLF1 View Post
          Just for comparison here is my plot for today from my FR24 supplied box and antennae.
          [ATTACH=CONFIG]4719[/ATTACH][ATTACH=CONFIG]4721[/ATTACH]
          Ben.
          Originally posted by Breitling View Post
          Mine one, almost 350 nm, near to overlap you being more than 1000 km apart.

          [ATTACH=CONFIG]4722[/ATTACH]
          Wow! Both of you got excellent coverage, the magic of FR24 supplied professional equipment.

          With my "Home brew antenna+amplifier+50 ft/15m cheap RG6 Coax+DVB-T USB Dongle", my NORMAL maximum range is about 270 nm, OCCASSIONALLY jumping to 350nm under favourable weather & atmospheric conditions.
          Last edited by abcd567; 2014-09-12, 00:11.

          Comment


          • Originally posted by abcd567 View Post
            Wow! Both of you got excellent coverage, the magic of FR24 supplied professional equipment.

            With my "Home brew antenna+amplifier+50 ft/15m cheap RG6 Coax+DVB-T USB Dongle", my NORMAL maximum range is about 270 nm, OCCASSIONALLY jumping to 350nm under favourable weather & atmospheric conditions.
            It is also very much down to location, I am on high ground with a slight hill to the south west, Breitling appears to be on a high point with completely unobstructed views 360-degrees around.
            Ben.
            FR24 F-EGLF1, Blitzortung station 878, OGN Aldersht2, PilotAware PWAldersht, PlanePlotter M7.

            Comment


            • It is accepted as essential to get the antenna clear of obstructions in all directions. I feel it is good to get a little more height if possible to get clear of clutter too where you may get reflected signals interfering with direct ones.

              Comment


              • Originally posted by peterhr View Post
                It is accepted as essential to get the antenna clear of obstructions in all directions. I feel it is good to get a little more height if possible to get clear of clutter too where you may get reflected signals interfering with direct ones.
                You are right. increasing antenna height improves both on obstructions & clutter.
                Since I cannot increase antenna height (live in an apartment), my only chance is that the city council decides to create a soccer field, park, community hall, and public library, acquiring the land by demolishing all high-rise buildings around my building
                Last edited by abcd567; 2014-09-12, 14:30.

                Comment


                • Sleeved Dipole With Amplifier ..
                  Antenna+Amplifier assembly will fit inside 1-1/4 inch or 1-1/2 inch PVC Pipe for Outdoor Mounting


                  Amplifier Gain: 13-18 dB
                  Coax Cable between antenna & receiver: 50 ft/15 m RG6, Cheap Quality.


                  Step 1 of 3 - Design & Simulation





                  Step 2 of 3 - Construction





                  Step 3 of 3 - Trial Run 2 hrs

                  Last edited by abcd567; 2014-09-12, 16:41.

                  Comment


                  • In my last post above, I have used 3/4 inch copper water pipe, as the 1/2 inch & 3/4 inch sizes are most commonly available.
                    However, the antenna gain and coverage increases with increase in copper pipe diameter.
                    If larger size (1 inch or 1-1/4 inch or 1-1/2 inch) copper pipe is used, it will give better coverage, and the assembly will still fit inside a 1-1/2 or 2 inch PVC Pipe.

                    Comment


                    • Two types PVC pipe end caps, to protect antenna and amlifier inside the pipe, from rain water & moisture.

                      The #1 end cap seems better for both upper & lower ends of pipe, as it is glued to the pipe by a special adhesive for pvc pipes & couplings. Once glued, the lower endcap will not be dislodge by downward pull of coax or weight of antenna+amplifier assembly.

                      # 1 15219747735_540bf38607.jpg ......# 2 15033160628_e01028c355_b.jpg
                      .
                      Last edited by abcd567; 2014-09-16, 15:27.

                      Comment


                      • I'm wondering (looking at Step 2 of 3 - Construction photo).
                        If you flipped the jar lid over and mounted it below the bracket, then screwed the jar (plastic?) onto the lid, you could then place your dongle
                        inside the jar "lessen the loss from the RG6" and run a USB cable from jar to computer.

                        Comment


                        • Originally posted by T-KJAN4 View Post
                          I'm wondering (looking at Step 2 of 3 - Construction photo).
                          If you flipped the jar lid over and mounted it below the bracket, then screwed the jar (plastic?) onto the lid, you could then place your dongle
                          inside the jar "lessen the loss from the RG6" and run a USB cable from jar to computer.
                          It is a good suggestion, but the distance between my antenna & desktop is too large for a USB cable.

                          Last year when I setup my system, I first tried to place DVB-T dongle close to antenna and ran 50 ft USB cable to my desktop computer. It did not work. I then used a laptop and started moving it towards the antenna in steps of 5 ft, trimming the USB Cable 5ft every time, till my laptop travelled 20ft towards antenna, and USB cable length was 30ft. At this point USB cable started working.

                          Since I cannot move my desktop to within 30ft of antenna, I decided to go for an Amplifier very close to antenna and run a coax. This solution worked very good.

                          My system now mimics most other hobbyist: Antenna at roof/mast, receiver+desktop down in the living room, and a long coax connecting the two.
                          Last edited by abcd567; 2014-09-13, 01:03.

                          Comment


                          • Now I recalled how I did the "trimming" of USB Cable mentioned in my last post.

                            I could not find a 50ft long length of USB extension Cable. The maximum available extension cable length was 15ft. I already had two extension pieces, 6ft & 12ft. I purchased 2 of 15ft extensions, and joined all 4 togather, making total length 48ft. It did not work. I removed the 6ft one, making total length 42ft, and moved laptop to suite 42ft. It did not work. I then removed 12ft piece and put back the 6ft piece, making total length 36ft. It did not work. I then removed the 6ft piece, and used only 2 of 15ft length, making 30ft, and it started working. I then tested 6ft and 12ft pieces separetally one by one to see if any of these were defevtive, but both worked ok.

                            The above experiment established that maximum length for which USB Cable works is about 30ft.

                            Comment


                            • The longest USB extension cable that I have seen WITHOUT an active repeater is 25ft.
                              The longest I have seen WITH an active repeater is 48ft.

                              Active repeater gets power supplied from the USB port on the computer as well as the port on the device. (i.e printer for example)

                              Comment


                              • Originally posted by T-KJAN4 View Post
                                The longest USB extension cable that I have seen WITHOUT an active repeater is 25ft.
                                The longest I have seen WITH an active repeater is 48ft.

                                Active repeater gets power supplied from the USB port on the computer as well as the port on the device. (i.e printer for example)
                                Thanks for the information. The stores in my neighborhood do not have USB cable longer than 15 ft. Maybe if I tried on-line stores like ebay or amazon, I could get 25ft long USB cable. I solved length problem by combining 4 short lengths to get 48ft (15+15+12+6). If I had found 25ft, I would join 2 lengths to get 50ft.

                                The real issue is loss of signal with length, which imposes a limit on maximum length of usb cable (about 30 ft). Active repeater is a good solution to overcome long length issue. I am sure many forum members are using it. I vaguely remember member peterhr (or maybe someone else) once mentioned something like this for his setup.

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