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  • @tvengineer:
    Thanks a lot for detailed description.
    Last edited by abcd567; 2014-07-26, 04:23.

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    • Originally posted by abcd567 View Post
      @tvengineer:
      Thanks a lot for detailed description.
      If you think it works pretty well, I will do up a post to explain how to make it in detail.
      The only part I am not real happy with right now is attaching the feed. I used RG 6 to feed it and with the element spacing so small there is not much room to fiddle around with soldering the cable.. and i don't think anyone can get solder to stick to the braid on RG6.. I need to find a smaller cable, maybe RG59 with copper braid..
      Also... some of the websites about Jpoles mention making 5 loops in the feed coax to make a balun.. something about keeping energy off of the shield.. I have not tried that yet... might only be important for VSWR when transmitting.

      Like I said a few posts back.. It might not be technically correct.. might not have good SWR or what ever.. but it seems to work and I am not complaining about that :-)

      :-) I was worried that the first one might have just been a happy mistake .... so I made 2 more to make sure that they acted the same :-)

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      • Originally posted by tvengineer View Post
        .........The only part I am not real happy with right now is attaching the feed. I used RG 6 to feed it and with the element spacing so small there is not much room to fiddle around with soldering the cable.. and i don't think anyone can get solder to stick to the braid on RG6.. I need to find a smaller cable, maybe RG59 with copper braid.. ..
        Try the method shown in image below:

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        • . you can coil the center stub to make if look like the one in the picture and it will fit inside of a PVC tube.
          Dont forget all these antennas will need to be retuned -with a test meter - when placed inside a pvc radome, otherwise yes we are only guessing
          Mike

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          • Originally posted by tvengineer View Post
            I find that making the Colinear ones is very if'y... they are easy to put together, but to get them to work with good solid connections is difficult...........

            .....I think I have found my "best" antenna in the J pole..
            You are right. CoCo is very if'y.

            I have found my best Antenna in Franklin Collinear Dipole, with impedance matching stub, and I am very satisfied with it.

            I have noticed that almost everyone wants an antenna which can fit inside a PVC pipe. Ok it is convenient, but non-pipe antennas are there for so long & so successful. The common example is "On the Air TV" antennas, which used to be on roof of every house before satellite & cable TV took over.

            Wire/tube antennas are predictable, can be cut precisely, and easy to make. Just because these do not fit inside a pipe, while CoCo does, almost everyone is ignoring these and trying hard to built a successful CoCo, but most fail because of it's if'y nature.

            Some are trying to modify wire antennas to fit inside a pipe. Good attempt, but the biggest hurdle is the phasing line (or delay line as some call it). The only delay line which is easily constructable by an amateur, yet precise, is a quarter wave stub. A phasing coil or folded stub made by an amateur will rarely be precise enough to give good performance. This can only be done in factory environments with manufacturing templates and costly tuning/testing equipment. Factory made antennas extensively use phasing & tuning coils.

            If one stops insisting on "inside the pipe" antennas, lot of good choices are available like 1/2 wave dipole, folded dipole, JPole, Franklin Collinear Dipole, Slim Jim, Sleeved Dipole etc etc.

            Our TV antennas on our home rooftop used to survive wind & weather. Why can not our 1090 MHz wire/tube antenna survive the weather and wind?
            Last edited by abcd567; 2014-07-26, 11:57.

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            • I think you're wrong ... people want an antenna they can put up a mast and it will stand up to a bit of weather - but they also want recommendations on how to mount it and waterproof the connections.

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              • Originally posted by tvengineer View Post
                The black rings are 100 nm....

                The top is 1/2 wave (134mm) the phasing stub is the same 134mm..
                To make it .. measure up from the bottom of the J to the top of the first element (I don't have my numbers in front of me but I think it was 188 mm) make a 90 degree turn.. measure another 134 mm and make another 90.. find the center of the middle section and bend it back on itself so that the top element is back on top of the bottom element (straight up and down antenna with a 1/2 stub sticking out the middle... that is it.. you can coil the center stub to make if look like the one in the picture and it will fit inside of a PVC tube.
                Originally posted by YWYY View Post
                Dont forget all these antennas will need to be retuned -with a test meter - when placed inside a pvc radome, otherwise yes we are only guessing
                Mike
                I have run computer simulation of 4-element franklin for:
                (1) Straight stub
                (2) Folded stub (coil dia 20mm)
                (3) Folded stub (coil dia 10mm)

                Please see below the simulation output of all three, which shows the effect of folding the stub.

                1 of 3 : Franklin Collinear with straight phasing stubs
                Franklin Flat Stub.png


                2 of 3 : Franklin Collinear with phasing stubs folded as a coil of 20mm dia
                Franklin Folded Stub 20mm dia.png


                3 of 3 : Franklin Collinear with phasing stubs folded as a coil of 10mm dia
                Franklin Folded Stub 10mm dia.png

                Note: I have not included the "Impedance Matching Stub" at the center of the antenna (feed point) to simplify the study. Adding Impedance matching stub will reduce SWR, but will not affect Pattern & Gain.

                .

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                • Originally posted by peterhr View Post
                  I think you're wrong ... people want an antenna they can put up a mast and it will stand up to a bit of weather - but they also want recommendations on how to mount it and waterproof the connections.
                  How the TV antennas on our home roof-top were protected? these were not protected at all. Only cable/twin lead connection used to be inside a small weather proof terminal box.

                  The antenna itself being made of thick wire or copper/aluminum tubing does not require any protection.
                  Only the cable connection point need to be protected.

                  Please see pictures below how someone has protected his Thick-Wire antenna.

                  franklin_7.JPG . franklin_8.jpg . franklin_3R.png

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                  • Originally posted by peterhr View Post
                    I think you're wrong ... people want an antenna they can put up a mast and it will stand up to a bit of weather - but they also want recommendations on how to mount it and waterproof the connections.
                    Here is another example of two antennas installed outdoor without PVC pipe, by forum member "lutorm" (post # 993).
                    The big one is a 2 meter band J-Pole made of Copper pipe,
                    The small one (on horizontal arm right of J-Pole) is a 1090 MHz Franklin Collinear made of thick wire. The Line amplifier is near the start of the horizontal arm:

                    Last edited by abcd567; 2014-07-26, 23:39.

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                    • That's the one to go for - if only we had forum messaging - we need that split out from this long thread and put as the head of a thread on its own to make it easy to find, then it can have it's own Q&As following.

                      That's a design that will work for both hi-rise buildings (with no access to the roof) and for mast mounting.

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                      • This weekend was a lot of work. Not wanting to spend a fortune on this "hobby" of ours, I made do with what was available, and ended up with a not too crappy job.

                        Collinear Antenna is now 15m above ground, feeding down with the amp at ground level. Feeding down to the amp at ground level.
                        After running on this new height, I can say that I added another 50km of range, bringing my average outer perimeter to about 400km on the busier side (as per FR stats: 215nm). After running for about 48 hours, the plot will be much clearer, but I have already seen changes to the overall plot produced by adsbScope (which is used to keep track of the perimeter).
                        Plan is to change the top part and build a kind of bracket with PVC fittings to accommodate three antennas at the top. PVC fittings wont add much weight and the existing 20mm conduit that I use to cover the antenna, can fit into it without need for any other hardware.

                        J-pole
                        For the mere fun of it, I took a copper rod and bent myself a J-pole, as described by TVEngineer. Used the link supplied by LEXJ to confirm the dimensions. This little one is about 5m above ground and already gives better reception than the last collinear I built, as per ABCD's new calculations. Sorry Mr ABCD - I trust your calculations and formula's ... but like you said: Coco's are very iffy! The J just picked up traffic 250 km away, yup, no typo made. Still rather amused at how good my very 1st coco is working, compared to the about 8 or so others that followed, where I tried to better its reception. Have the same test setup I use for all the new antennas, hense height, location and feed cable is a constant.

                        Still to come...
                        Pole to come down (controlled action ) to add the top mounting bracket, slot in the trusty OLD coco, add the new J-pole and also add a Franklin, wire each of them. Slap on more paint and up she's goes... can then add another amp to either of the two new antennas, and then compare performance and range. At least when one antenna fails, there are two standby's. Just not sure how to house the Franklin - safe to spray paint it? (Bare copper will oxidise!) Also not sure if I want to add the amps at the top, or keep them at the bottom. Thinking about running the feed lines IN the metal pipes, away from wind and weather and also shielding it from other signals.

                        Thanks to all the different forum members who contributed ideas, results, research and personal experiences regarding antennas!

                        PHOTO: Longest pole needs no explanations .... the one on the side of it is a wideband Discone. Other gadgets that can be seen is a Oregon Scientific Personal Weather Station and a solar powered light.

                        IMG_20140727_142945-crop.jpg
                        Last edited by HermanZA; 2014-07-27, 21:36.

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                        • @HermanZA:
                          CONGRATULATIONS for a successful enhancement to your installation.

                          Good idea to have more than one antenna as standby.
                          Franklin requires precise dimensioning, cutting & bending to get good results.
                          The center-to-center distance between horizontal parallel arms of phasing stub need to be accurate, specially that of Impedance matching stub.

                          Forum member "Trigger" has made successful Franklin by making it precisely dimensioned. I hope he will come up and give some fabrication tips from his experience.

                          In my opinion a thin layer of paint on Franklin should not affect its performance.

                          First try the Franklin at 5m above ground level before mounting it on pole. You may need to adjust the cable tap position few mm left or right of designed position to get best results.
                          Last edited by abcd567; 2014-07-27, 21:24.

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                          • .
                            Has anyone tried this antenna?

                            http://qsl.net/py4zbz/adsb.htm#b

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                            • When constructing the Franklin, I will use the same method to bend the wires like I used with the J-pole. Use a 6mm drill bit and "fold" the rod around it, then use a vice grip to confirm the bend radius, using the drill bit to check that you have even spacing between the two legs. Easiest method that I could think to get a pretty neat 6mm gap. Seems like it worked!

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                              • Originally posted by HermanZA View Post
                                When constructing the Franklin, I will use the same method to bend the wires like I used with the J-pole. Use a 6mm drill bit and "fold" the rod around it, then use a vice grip to confirm the bend radius, using the drill bit to check that you have even spacing between the two legs. Easiest method that I could think to get a pretty neat 6mm gap. Seems like it worked!
                                Your method of bending is practical & good.
                                Franklin requires less gap. A good center-to-center distance for stubs is 5mm, which makes the gap, for a wire of 2 mm dia = 5 mm - 2mm = 3 mm. Use a drill of 3mm dia. If this gap is too narrow and you feel the wires may touch, increase the gap. The 6mm gap is good mechanically, but smaller gap gives a better SWR and closer impedance matching.

                                What is the diameter of wire you have used for JPole & Franklin?

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