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  • Neat U-Bend & L-Bends (and a neat soldering job)

    Last edited by abcd567; 2014-09-24, 06:51.

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    • I received the price of this antenna:

      http://www.taiwan-antenna.com/front/...tenna-N-Female

      It costs 78 usd + shipping + taxes

      Honestly I do not think good price

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      • Originally posted by trigger View Post
        Hi gregy,
        I have made a few Franklins and found them to be superior to any of the CoCos I've made. I first made this one. I then made another but added an extra couple of vertical segments and stubs. The diameter of the wire I used was 1.5mm. As with any antenna, accuracy is king.

        Later models used the spec as in this post http://forum.flightradar24.com/threa...ll=1#post56957 with the slightly longer matching stub.
        Which design/model gave you the best results?

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        • hi abc567
          dug out the caliper for accuracy
          brass rod diamater = 2.5mm
          gap between brass rod = 5.0mm

          i tried smaller gap - however the radius of bend is to severe and brass fractures
          5mm appears to be reproducable and reliable from fracture of brass

          if you could model with 2.5mm brass and 5mm gap between phasing and matching stubs
          and for 50ohm

          much appreciated thx
          Last edited by gregy; 2014-09-24, 16:11.

          Comment


          • Originally posted by gregy View Post
            hi abc567
            dug out the caliper for accuracy
            brass rod diamater = 2.5mm
            gap between brass rod = 5.0mm

            i tried smaller gap - however the radius of bend is to severe and brass fractures
            5mm appears to be reproducable and reliable from fracture of brass

            if you could model with 2.5mm brass and 5mm gap between phasing and matching stubs
            and for 50ohm

            much appreciated thx
            Is 5mm the gap between surfaces of stub wires or is it center-to-center distance between stub wires? I mean "did you use 5mm drill bit as a mandrel for U bends?"
            Last edited by abcd567; 2014-09-24, 19:16.

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            • 5mm is the internal gap between stub wires (same as bending around 5mm drill)
              hence spacing between "centre of wires" in phasing and matching stub (for 2.5mm dia rod) would be
              5+1.25+1.25 =7.5mm

              thanks greg

              Comment


              • Originally posted by gregy View Post
                5mm is the internal gap between stub wires (same as bending around 5mm drill)
                hence spacing between "centre of wires" in phasing and matching stub (for 2.5mm dia rod) would be
                5+1.25+1.25 =7.5mm

                thanks greg
                Thnx for information. I will do modelling, simulation & optimization during this week end, and post results.

                I will also model, simulate & optimise for 1.6mm dia wire (or is it 1.5mm dia wire?). I feel it is easier to use thinner wire, as it is easir to make a neat & sharp bend. I use 1mm dia wire for all my antennas.

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                • confirming the copper wire as measured (caliper) 1.6mm dia
                  (id assume this is probably AWG 14 (nominally 1.62mm) )

                  obvoiusly much smaller gap (2.5mm min?) is possible with this wire ... hence optimise it for best match/performance

                  i will make antenna from both brass rod and Cu wire (Cu will be much easier to bend and get very accurate)
                  i will try to optimise match for both (50ohm) using VNA and post results

                  Comment


                  • @ gregy:
                    Franklin 4-element antenna.
                    wire dia = 2.5mm, gap between conductors of phasing & impedance matching stubs = 5 mm.

                    Gain = 5.8 dBi, SWR (50 ohms) = 2.37.


                    Gain Pattern SWR - Frankiln 4-element 2.5mm dia wire 5mm stub gap .png . SWR Sweep-Franklin 4-lement-2.5mm wire dia-5mm stub gap.png . Franklin 2.5mm dia wire Template.jpg . Click here to see large size layout drawing.
                    Last edited by abcd567; 2014-09-28, 04:15.

                    Comment


                    • ABCD567 ... thanks for the modelling - i will get now get to the workshop!
                      actually have been there all morning...
                      fitted the LNA on coco and currently running a test... however wind has picked up and messing with my
                      temp mast arrangement (pvc pipe is flexing ) .. so its not a fair comparison given the antenna movement im seeing.
                      LNA has definitely improved coco ramge.. although not by as much as I expected ...hence suggesting that im at limit of range for my given antenna height (i have quite low loss feeder .. hence the LNA benefit for the feeder loss in much less)

                      i also put together a 1/4 wave ground plane (eg like the spider antenna . but only 4 radials at present)
                      messing around with length whip and bending downwards ground radials, i matched it to VSWR 1.4
                      and have range checked it... not as good as coco (as expected) ... but i now have it as a reference antenna also.

                      much appreciated the modeeling.

                      Comment


                      • @ gregy:
                        Franklin 4-element antenna: a better SWR with thinner wire & narrower gaps.
                        wire dia = 1.5mm, phasing stub gap = 3mm, matching stub gap = 2mm

                        Gain = 5.38 dBi, SWR (50 ohms) = 1.63.

                        Cable Tap at 55mm from vertical limb (adjust for best results).

                        Click here to see post #1378

                        Click here to see post #1380




                        Gain Pattern SWR - Franklin 4-lement-1.5mm wire dia-3mm phasing stub gap-2mm matching stub gap.png . SWR Sweep-Franklin 4-lement-1.5mm wire dia-3mm phasing stub gap-2mm matching stub gap-2.png . Franklin 1.5mm dia wire Template.jpg . Click here to see large size layout drawing
                        Last edited by abcd567; 2014-09-28, 04:16.

                        Comment


                        • Originally posted by abcd567 View Post
                          Here is you drawing, revised to give full information you require:


                          Originally posted by peterhr View Post
                          I'd not do (1) the down lead will pick up noise in competition to the signal before both are amplified - in fact I'd only use (1) with no amplifier.

                          I'd probably not do (3) since it has an extra thing that will reduce signal (don't know if every connector = 2db loss rule applies).

                          (2) wins - maybe slip a sleeve over the copper and smother the bottom and end of sleeve in silicon chalk (bathtub stuff) - that will come off again with determination - there' s 1001 ways to do this.
                          I've completed Setup 2. Exactly what you see on drawing.
                          Down in the office DC power 15v adapter, Power inserter this one http://m.ebay.com/itm/281224823197, and receiver.
                          Up on top of the roof Pepsi can antenna with Amplifier inside the Pepsi can.

                          Now I wonder what is this? Powersupply_Amplifier_Antenna.png Good or bad ?

                          Comment


                          • Originally posted by 747-8F View Post
                            I've completed Setup 2. Exactly what you see on drawing.
                            Down in the office DC power 15v adapter, Power inserter this one http://m.ebay.com/itm/281224823197, and receiver.
                            Up on top of the roof Pepsi can antenna with Amplifier inside the Pepsi can.

                            Now I wonder what is this? [ATTACH=CONFIG]4822[/ATTACH] Good or bad ?
                            I have never used SISEX facility of RTL1090, and don't understand it either.

                            I judge the antenna's performance by:

                            (1) RTL1090's main window:
                            (a) Air Data - Packet Rate
                            (b) Signal Strength
                            (c) Number of Aircrafts

                            (2) Maximum Range plot by "adsbScope" and/or "Virtual Radar Server" after running these for couple of hours (preferably 24 hrs).

                            Please see attached screenshots:

                            14974633457_d4af8b0df1_o.png . 14974468847_49a479c355_o.png
                            Last edited by abcd567; 2014-09-28, 01:24.

                            Comment


                            • abd567
                              an update.. started the bending of the brass rod, overall length per your diagram just under 1m (lenght of rods)
                              however getting high accuracy in the phasing and matching stub lengths with all bends from single rod is the challenge
                              after a couple attempts, ive made the antenna in three sections - can thus adjust the length of the vertical
                              radiator 138mm sections be welding the peices.
                              eg first steps are to bend each of phasing sections around 5mm mandrel, then the 90degree bends - the top and botom
                              radiator are trimmed to exact dimensions and the inner sections adjusted by welding the antenna peices
                              together. im sure with practise it would be possible to estimate all the bend lengths and adjust accordingly....
                              its a work in progress, unfortunately im travelling overseas for next 2 weeks, so will get onto final step of attaching
                              coax and tuning when im back.
                              thanks for the addditonal simulation, this will certainly be easier to construct ... but will need some spacers to
                              hold stub gaps (perhaps some expoxy? i will dig into junk box for some perspex/acrylic peices)
                              will post updates in 2 weeks

                              Comment


                              • Originally posted by gregy View Post
                                abd567
                                an update.. started the bending of the brass rod, overall length per your diagram just under 1m (lenght of rods)
                                however getting high accuracy in the phasing and matching stub lengths with all bends from single rod is the challenge
                                after a couple attempts, ive made the antenna in three sections - can thus adjust the length of the vertical
                                radiator 138mm sections be welding the peices.
                                eg first steps are to bend each of phasing sections around 5mm mandrel, then the 90degree bends - the top and botom
                                radiator are trimmed to exact dimensions and the inner sections adjusted by welding the antenna peices
                                together. im sure with practise it would be possible to estimate all the bend lengths and adjust accordingly....
                                its a work in progress, unfortunately im travelling overseas for next 2 weeks, so will get onto final step of attaching
                                coax and tuning when im back.
                                thanks for the addditonal simulation, this will certainly be easier to construct ... but will need some spacers to
                                hold stub gaps (perhaps some expoxy? i will dig into junk box for some perspex/acrylic peices)
                                will post updates in 2 weeks
                                At ads-b wavelength of about one feet/30cm (27.5 cm exactly), stub gaps are in few millimeters. Using thick wire therefore becomes a real challenge to achieve accuracy. That is one of the reasons I use 1 mm dia wire (18 AWG - the core of RG6 Coax). The additional advantage of thin wire is that thin wire antenna has a narrower bandwidth than the thicker wire antenna. This helps in better rejection of "adjuscent channel interference" from cell phone signals, and is an advantage if a cell phone antenna is nearby.

                                The down side of thin wire antenna is that it is mechanically weak and cannot be mounted outdoor, unless protected by a housing or radome. Because of much longer wavelengths (compared to ads-b), the on-the-air TV antennas are made of aluminum tubes of about 10mm dia and are mechanically strong, and are mounted on roof of a house without any protective housing or radome.

                                I live in an apartment, without a balcony or open-able window, so my installation is strictly indoors. My antennas therefore don't require mechanical protection.

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