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HomeBrew 1090 mhz single dipole Yagi Project

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  • HomeBrew 1090 mhz single dipole Yagi Project

    I have been building 3 homebrew 8 director single dipole yagis to replace the Chinese ones supposedly for the 800-900 GSM. Gain on the previous ones was less than expected.

    The Chinese GSM yagis only obtained about 1/3 of the signal strength of a simple omni in the main lobe and didn't even come close on maximum range.

    While appearing to be well made of the proper durable materials the Chinese antennas had no taper to the director lengths and the spacing was entirely wrong for 1090 mhz.

    Unless you are a AARL handbook geek, download a program that will help you design your "Perfect" yagi. I thank John Drew for making this calculator available. http://www.vk5dj.com/yagi.html

    Scrounging for materials:

    First off, you have to see what is available in your area for boom material and material to make the elements out of.

    It will be handy to have a tubing cutter for thick wall aluminum tubing if found or if solid stainless rod is found a cutoff wheel with a thin thickness to attach to your bench grinder. You also need a micrometer to measure the tube lengths in fractions of a millimeter. Your tape measure has a centimeter scale but that is just a guesstimate when it comes to decimal millimeters.

    I found my 1" boom material in an aluminum window shop. I found stainless steel rod in a hardware. I found antenna standoffs in an electronic store along with RG59 cable and connectors. You will have to decide whether to use pop rivets or bolts to hold things together.

    Since 5/16" stainless steel rod was all that was available locally that was close to 8 MM which the design program used.
    uses millimeter dimensions.

    Single or double dipole

    John Drew's program gives the dimensions for both but if you decide on the double dipole that will entail bending tubing precisely with a tubing bender. I chose the single dipole for simplicity sake and I didn't want to buy a tool for a one time project.

    Oxidation

    Water and weather cause aluminum to oxidize and if you are relying on rivets or bolts for grounding you need to seal them at the contact points. I will use marine epoxy and hopefully what is, will be what is for years to come.

    Does a Verticle Polarized Yagi have an UP & Down?

    From information I have gathered the answer is yes. The UP element is the one connected to the feedline center conductor. Accordingly, if the mounting is UP the wave pattern will be from the boom UP. Conversely, if the yagi is mounted with the feedline center conductor connected to the bottom half of the dipole the wave pattern will be from the boom DOWN. As you can see from my disclaimer I don't know this is FACT.

    The yagis are built and I'll do rudimentary testing today from the ground. Stay tuned!

    John
    T-RPVD1

    The world’s most popular flight tracker. Track planes in real-time on our flight tracker map and get up-to-date flight status & airport information.

  • #2
    I'd like to know the performance difference between :
    a dipole,
    a monopole over a surface plane (diagrams I've seen suggest the peak sensitivity is a doughnut at an angle of maybe 10-30 degrees above the plane)
    a monopole over a cone (sort of somewhere between over a plane and a dipole where the cone is reduced to a stick)

    also interested in what to do to create a balun - to make a balance dipole (which is a balanced antenna) work with maximum efficiently with a co-axial cable (an unbalanced feed)

    Sine we're talking about Yagi's mounted for vertically polarised signals, how wide (horizontally) is the acceptence pattern (have visions of six yagi's on a mast under a simple dipole feeding 7*rtl-usb tuners + 7*Raspberry Pi covering a huge area)

    Comment


    • #3
      Just adding my 2 cents,

      my experience with a 1090mhz tuned 13 element yagi with H155 cable and balun is that... it's goes AWOL when it rains i.e. cannot see any planes. YMMV.

      Comment


      • #4
        Originally posted by North Borneo Radar View Post
        Just adding my 2 cents,

        my experience with a 1090mhz tuned 13 element yagi with H155 cable and balun is that... it's goes AWOL when it rains i.e. cannot see any planes. YMMV.
        Could you expand on that?

        Do you have a close-up picture?

        John

        T-RPVD1

        Comment


        • #5
          Originally posted by paradiselost View Post
          Could you expand on that?

          Do you have a close-up picture?

          John

          T-RPVD1

          Hiya John,

          Please see http://radarspotting.com/forum/index...ic,2181.0.html

          I built it based on the planeplotter group's DIY Yagi in the folder section (?or files?) that I found.

          As for not seeing planes during and just after rain... I have no idea. I recall I read it somewhere that apparently it does happen, due to rain noise. This seems to be the weakness of yagi. However, it was a fun adventure building and installing it and finding what a yagi does and does not. Perhaps it's made me think outside the box making a DIY Yagi.

          Your findings might be different, who knows.

          All the best.
          Last edited by North Borneo Radar; 2013-08-09, 00:15.

          Comment


          • #6
            A quick update.

            Installed another 20 ft extension to the mast. Guy wires today then will test out the 3 yagis. Overnight, the extra mast seems to have increased my range in some areas 50 NM. Hope the yagis perform.

            North Borneo Radar, looked at that link and was impressed. Don't think my antennas will experience rain fade since the elements are solid stainless steel.

            Will update Sunday.

            John

            T-RPVD1

            The world’s most popular flight tracker. Track planes in real-time on our flight tracker map and get up-to-date flight status & airport information.

            Comment


            • #7
              Hiya John,

              good work mate. I do noticed increased range from your feed. indeed height is king for ADS-B. You are using a DIY omni right? At my location somehow adding more height didn't help so I kept the height to the minimum so the antenna and mast will be ok on a windy day.

              Yes, I suspect with a different element (SS) it should make a difference. Let's see what happens and good luck.

              On another note... Francois/F5ANN who is active on the mode s beast group and also the creator of the PCB Antenna (both sold by JMZ and 1090mhz.com) is working on an active PCB antenna with SAW filter. Initial test is promising. I have the PCB antenna which performs well as a omnidirectional antenna and got it direct from Francois so the price was good. Worth considering the active PCB antenna once we know the performance of it so keep an eye for news about it John.

              All the best

              P/S: Oh by the way... very good points stated by yourself on the other thread : FR24 boxes privileged over other feeders/receivers. Thumbs up! both!
              Last edited by North Borneo Radar; 2013-08-09, 23:44.

              Comment


              • #8
                Very interested to see results

                Some years ago, I did knock up a parabolic reflector for wifi - It occurred to me that this might make an interesting little project for 1090Mhz for someone who has some time who wanted a directional antenna.

                Here an article about construction of the parabola http://www.ab9il.net/wlan-projects/wifi2.html

                For my wifi reflector, I used aluminium foil from the kitchen that I'd put through a document laminator - to make up a big sheet, think of fish scales glued together rather than a bigger laminator (this might need three support struts rather than the one - but would still be cheaper than a sheet of aluminium)

                The antenna could be a simple dipole or an extension of that ... a centre fed collinear supported by a plastic frame attached to the top and bottom edges of the parabola.

                ---

                Or fitting a dipole at the focus of a satellite dish (where the elements of the antenna in the LNB would have been) - though the feed arm might get in the way (replace by an assembly made of rigid plastic conduit - drilled, cable tied and made rigid with hot-melt glue)

                Comment


                • #9
                  Originally posted by paradiselost View Post

                  Will update Sunday.
                  It is Sunday in parts of the world.

                  1. I added a 20' section to the mast bringing the height of the 5 Db omni to about 82' above sea level. See the annotated Pics for details.

                  2. Due to time constraints the yagis were mounted at the 20' level so I could get at them in case of needed adjustments. Getting guywires in place were the primary concern before dark set in.

                  3. A 30' piece of bamboo was used as a gin pole to hoist the extra 20' mast in place and stabilize it until it could be properly guyed. Climbers here in Paradise use their bare feet, arms and hands to climb antenna masts. It takes one climber and 3 interpreters to tell him what to do.
                  UP, Down, Around are not in their vocabulary in those words so interpreters are vital.

                  4. Since I am a firm believer in the 5 Ps, I looked at what my potential was before spending my pension. http://www.heywhatsthat.com/main-090...?view=ML2O2PSQ

                  On the terrain map lower on the page click on Up In The Air. Once you do that scroll the map out until you see all of the Blue lines around my area. That is the maximum range for 30,000 feet. The Yellowish line is the maximum range for 10,000 feet. Play with those numbers and see your potential. You can select frequency, line of sight or curvature of the earth above the map and observe how the maximum range changes. Compare theoretical with your own maximum range charts produced by you basestation program.

                  John

                  T-RPVD1

                  The world’s most popular flight tracker. Track planes in real-time on our flight tracker map and get up-to-date flight status & airport information.
                  Attached Files

                  Comment


                  • #10
                    Addition details to the 1090 mhz yagi project

                    The yagis are at the 20 ft levels of the mast and have been operating about a week. The active element of the dipole is UP vertical on all the yagis. One yagi is generally in the Northwest direction and another is North-northeast and another is South-southeast.

                    All track fairly well although I have not made adjustments to the radiator-reflector spacing from the original 55 mm. Maximum range is about 50 to 125 miles.Pictures show details.

                    Things I have learned by Doing

                    1. Coax available to me has aluminum braid which is impossible to solder with 60/40 rosin core solder without tinning with aluminum paste or solder first. Braid twisted together to make the grounding will oxidize and make a poor electrical connection left in the atmosphere even when sealed in epoxy. All of my directors and elements with the exception of the radiator rely on the aluminum boom for grounding. I have sealed the screw heads of the bolts and the washers and nuts with epoxy but it remains to be seen how long lasting this will be.

                    2. I have made a slot in the boom which attaches the radiator so that I can move it either closer or farther from the reflector.

                    3. The three yagis connect to a 3 way combiner and then through a 1090 mhz band pass filter before attaching to the dongle.

                    3 The omni connects to the dongle through its own 1090 mhz passband filter.

                    The passband filters work because SDRSharp will only allow the strongest FM Station to be tuned and its bandwidth is severely attenuated. It also prevents tuning air to ground audio even tower 1/4 mile away.

                    Things Left to Do Before Moving to the Top of the Mast

                    1. I have a good idea what the beamwidth is from observing the points where the individual yagi pick up planes and then reach LOS (Loss Of Signal) so I will not change the azimuth or direction they are pointed until my testing and adjustments are through.

                    2. In he beginning I asked the rhetorical question as to whether the active radiator should be pointed UP or DOWN in respect to the boom. They are all UP now.

                    3. Being old and infirm I must rely on others to make the adjustments for me with involves translating "Rome was not built in a day" so whenever is whenever.

                    4. At the end of adjusting and testing I'll have to make the decision of WHAT IS is good enough.

                    It's been my pleasure sharing this project with you all.

                    John

                    T-RPVD1

                    The world’s most popular flight tracker. Track planes in real-time on our flight tracker map and get up-to-date flight status & airport information.


                    yagidesign.jpgSECEBUyagi.jpgnewyagimount.jpg
                    Last edited by paradiselost; 2013-08-16, 22:22. Reason: typo

                    Comment


                    • #11
                      Hi, My first post

                      I've been playing with the excellent yagi calculator by John Drew, but can't find how to change from a folded dipole to a flat one. Could someone explain how to do this please?

                      Camerart.

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