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  • I will attempt this coming weekend, to make a Franklin as per the latest specs. Will advise results, once I have to share. The 3mm rods I have, are 400mm in length, not sure if I will be able to find any longer 3mm wire/rods in this 1-horse-town of mine.

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    • Hi
      You MAY be able to get long thick copper rods 'earthing rods' from your builders supply store. I don't know what size they are as it's many years since I bought one, but one of them may do the trick.
      H.T.H.
      terry

      Comment


      • Originally posted by Teecee View Post
        Hi
        You MAY be able to get long thick copper rods 'earthing rods' from your builders supply store. I don't know what size they are as it's many years since I bought one, but one of them may do the trick.
        H.T.H.
        terry
        I bought one recently - it was about 9mm (3/8") and that was the thinner one

        I do have a coil of copper brake pipe ... that's 3/16" OD - 4.5mm - ABCD run the calcs on that some time ago and that was too thick to make a good antenna.

        It might also be easier to find aluminium rods in the right diameter. These can be softened with a gas blowtorch (heat to near melting point and cool slowly) only problem is that they're hard to solder - so would probably need some sort of mechanical (screw or crimp) connection for the down-lead (thread the innards of two connectors from a domino block on before bending)

        Have a look what is available in brazing wire - Ebay UK have it in 2.4 and 4mm diameter - 1m lengths, unfortunately it's sold in 2.4kg packs for 40 (that's about 65 USD)

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        • Hi Peter
          I can get brass rod & tube from a nearby hardware/model shop, it's obviously sold for OO model railway use, but I suspect it may be too thin for use as an antenna (I have 2 mm rod & 2.3 mm I.D. tube , axles for Dinky toys !, yes I am too old to play with them). My main problem is lack of co-ax (which to get 50 or 75 ohm) and inability to experiment. I need a good (out of the box) antenna with about a 10 meter lead for my SBS, when I go on holiday, but don't want to pay top money for them because if I can get it up on the roof (of the apartments) I'll probably have to leave it there (yes we do go to the same place every year).
          Meanwhile keep having fun
          Terry

          Comment


          • Originally posted by Teecee View Post
            Hi Peter
            I can get brass rod & tube from a nearby hardware/model shop, it's obviously sold for OO model railway use, but I suspect it may be too thin for use as an antenna (I have 2 mm rod & 2.3 mm I.D. tube , axles for Dinky toys !, yes I am too old to play with them). My main problem is lack of co-ax (which to get 50 or 75 ohm) and inability to experiment. I need a good (out of the box) antenna with about a 10 meter lead for my SBS, when I go on holiday, but don't want to pay top money for them because if I can get it up on the roof (of the apartments) I'll probably have to leave it there (yes we do go to the same place every year).
            Meanwhile keep having fun
            Terry
            The main reason you need the thicker material is so it will have sufficient stiffness to stay in shape in windy weather. On the other side it can't be too big a diameter since it affects the antenna tuning. If it is brass (or copper) it might need some protection to prevent corrosion.

            75 ohm cable is usually easy, and the connectors are readily available - it's TV downlead, but satellite disk cable is usually better quality. What is the input impedence of the SBS?

            Comment


            • Originally posted by peterhr View Post
              .........I do have a coil of copper brake pipe ... that's 3/16" OD - 4.5mm - ABCD run the calcs on that some time ago and that was too thick to make a good antenna........
              The 4nec2 Software shows very erratic results when wire diameter is too big. About 3 mm wire dia is it's limit for 1090 MHz (wire dia = 1% of wavelength).

              This can be because of either:

              (a) It is not possible to tune with very large dia wire in matching stub
              OR
              (b) The software 4nec2 is not capable to handle thick wires.

              I feel (b) is the reason.

              We may go ahead to make a 4-element Franklin with 3/16 " (4.76 mm) dia brake pipe, without the help of Software simulation.

              The tap position in this case has to be determined manually by trial & error...sliding tap along stub in steps of say a few mm at a time and running antenna for say 12 to 24 hrs at each position. This is painstaking.

              When I built my first Franklin with matching stub, I did not have the simulation software. I used this painstaking trial-and error method to determine tap position, which did succeed. Since my antenna was located at man's height inside my apartment, adjusting tap was easy .... loosen the screws of tap connector, slide connector 1 or 2 mm, re-tighten the screws. It was the large number of long trial runs which were painstaking.

              For any dia of wire/pipe:

              Length of wire/pipe in each of 4 vertical elements & 2 Phasing stubs = 1/2 wavelength = 138 mm

              Length of wire/pipe in Impedance Matching (Tuning) stub = 1/2 wavelength + Length of the bend = 138mm + Length of the bend
              Since bend is a semi-circle, it's length = pi x (gap+dia of wire)/2

              For 3/16" (4.76 mm) dia pipe , 6 mm gap, the Length of bend = 3.14 x (6 mm + 4.76 mm )/2 = 17 mm

              hence length of wire/tube for matching stub = 138 mm + 17 = 155 mm


              My Adjustable Cable Tap:
              (The connector screws are spaced at 5 mm center to center. This makes gap between 1 mm dia stub wires = 5mm -1mm = 4mm)




              .
              Last edited by abcd567; 2014-08-01, 16:35.

              Comment


              • I know very little about building aerials, (though my father used to back in the day).

                You might find this more to your liking? Its 3mm and available in different lengths from 300mm-1000mm

                http://maccmodels.co.uk/materials-me...00mm-long.html

                Comment


                • Originally posted by RAFF View Post
                  I know very little about building aerials, (though my father used to back in the day).

                  You might find this more to your liking? Its 3mm and available in different lengths from 300mm-1000mm

                  http://maccmodels.co.uk/materials-me...00mm-long.html
                  Thanx. This info is good for those living in UK (peterhr, trigger etc). I live in Canada. The postage from UK supplier to Canada will sure be high. I am trying to find wires/rods from local stores in my city.

                  I just returned from Canadian Tire Store in my locality. They have the 3/16" Brake Line, 4 ft long pieces, ideal length, and not very high cost ($7.99 + tax), but it is not made of copper. It is made of bendable alloy steel. I dont know what will be effect of a Magnetic material on the Impedance matching/Tuning stub. I will try other stores in couple of days to find a copper brake lining 3/16" dia, or solid copper wire 3mm or 5mm dia.

                  Edit: corrected typo 3/4" to 3/16". Thanks to Teecee.
                  Last edited by abcd567; 2014-08-01, 20:27.

                  Comment


                  • Hi Peter
                    Sorry for the slow reply had to go to a funeral.
                    Can't find anything in the SBS manual to tell me the impedence. (Kinetic SBS 1e)

                    abcd567
                    If your 3/4 " is not a typo, that is probably the pipe from the inlet manifold to the brake servo, not what you want at all.
                    They stopped making brake lines of copper (in the U.K.) around the late fifties and went to 'cupro-nickel', sorry I can't tell you more, but I would have thought that would be old -hat by now. When we make brake lines for the race cars we use the neoprene with braided outer (Goodrich/Goodridge, hoses you probably know them as), it's cheaper / easier / better than the genuine article.
                    Have fun
                    Terry

                    Comment


                    • Originally posted by Teecee View Post
                      .........
                      abcd567
                      If your 3/4 " is not a typo, that is probably the pipe from the inlet manifold to the brake servo, not what you want at all......
                      Terry
                      Yes, 3/4" IS a typo. Thanks for pointing it out. What I found at Canadian Tire Store is 3/16".
                      Last edited by abcd567; 2014-08-01, 20:30.

                      Comment


                      • I bought the brake pipe off ebay.co.uk ... it says its copper - it is the right colour but ive nit unwrapped it so who knows.

                        With the other materials, it's reslly a matter of identifing types of suppliers rather actual ones.

                        Comment


                        • Hi abcd567
                          I went to the model shop today for the 3mm copper rod, got brass, and guess where it comes from ?
                          K & S Precision Metals, Chicago. I see you are 'just the other side of the lake' from there
                          Seriously I don't know if that's any help, but if it is, 3/32 brass rod (3.97 mm) stock No 1163 comes as a yard long piece,they have a web site.
                          Just got to figure out how to bend it decently now.
                          H.T.H.
                          Have fun
                          Terry

                          Comment


                          • Originally posted by Teecee View Post
                            Hi abcd567
                            I went to the model shop today for the 3mm copper rod, got brass, and guess where it comes from ?
                            K & S Precision Metals, Chicago. I see you are 'just the other side of the lake' from there
                            Seriously I don't know if that's any help, but if it is, 3/32 brass rod (3.97 mm) stock No 1163 comes as a yard long piece,they have a web site.
                            Just got to figure out how to bend it decently now.
                            H.T.H.
                            Have fun
                            Terry
                            Thanks for the very useful information. I will check their website and prices for shipping to Canada.
                            Often US Suppliers charge exhorbitant shipping to Canada, almost same as for sending across the globe, although we are nextdoor.

                            Comment


                            • I went to many Stores who supply Electrical / Construction materials to contractors. They normally have all sizes and types of stuff.
                              Unfortunately I found all of them closed. Normally these are open on Saturdays, though shorter working hours.
                              Since Monday Aug 3 is aCivic holiday in Ontario, most contractors & the stores supplying them are not working on this saturday to give a long weekend (Sat, Sun, & Mon) to their staff.

                              I think it is the other way round. The Managers wanted long weekend, so the closed on Saturday also, telling owners & labour unions they have done it for the sake of their staff .

                              So I have to wait till next weekend to find the right stuff.

                              Comment


                              • Today I again visited Canadian Tier & Home Depots, which were open today.
                                From Canadian Tier, I purchased 3/16" dia, 4' long brake line. It is coated black from outside, but when I looked to it's end, the inside material is silver/aluminum/steel color.
                                When I brought it home, I checked it with a Magnet, and the magnet cling to it. Sure, it is made of a magnetic material (steel/steel alloy/nickle alloy etc etc). I am not sure how the magnetic material will affect the phasing & matching stub's performance. Anyway, I want give it a try.

                                Below are some photos of the Brake Line I have purchased:

                                DSC03204-R.jpg . DSC03205-R.jpg . DSC03210-R.jpg
                                Last edited by abcd567; 2014-08-02, 23:36.

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