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  • If you didn't power the amp it does nothing for you. In fact it makes it worse. See the diagram in post 1918 that shows dc injector and blocker needed for an amp. As for an antenna, stay with the one supplied with the DVD until you get everything up and running and the amp on line. That gives you a basis for comparison. Some folks are using a discone antenna while others are building a coaxial antenna http://www.balarad.net/ The type of coax is very important since the velocity factor makes the dimensions longer or shorter. Unless you put your antenna vey high and are in a lightening area I would forgo the lightening traps since they add a level of complexity. At least start without it, test, then progress to the traps. Good luck.
    Last edited by K5LEH; 2014-12-06, 14:12. Reason: Added information

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    • Originally posted by equi View Post
      ......no - i didn't powered the Amp ........
      Originally posted by K5LEH View Post
      If you didn't power the amp it does nothing for you. In fact it makes it worse....
      Last edited by abcd567; 2014-12-07, 02:14.

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      • Originally posted by zryder94 View Post
        ...........Also, if anyone is interested, I might be able to do some "legit" quantitave testing on a few different design concepts at work, in here:
        https://lh3.googleusercontent.com/-a...929_123848.jpg
        with this equipment:
        https://lh4.googleusercontent.com/-8...204_153715.jpg

        This chamber is used to do 3D field strength modeling of devices and antennas from 400mhz to 6ghz. for ADS-B uses, we would inject a signal into the antenna across a bandwidth around 1090Mhz, and test the radiation pattern being emitted from the antenna. This would give us antenna gain and radiation patterns to compare multiple design styles against each other.

        Let me know if you guys want to work something out, I would love to help out however I can.
        Thanks for your offer for support.
        If you have time, can you please test this very simple & easy to make antenna's performance (Gain, SWR, Radiation pattern etc):
        post #1224 on page #123 of this thread - "Another Experiment: A 1/2 λ sleeve dipole"

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        • I have been using the 4nec2 software for about a year for antenna modelling & simulation. This software gave very good results for simple wire antennas such as dipoles, franklins & yagis. It also seemed to give good results for cocos.

          Recently when I compared trial run results with simulation results of 8-element cocos, I found that the 4nec2 software gives around 10% error. It seems antennas with surfaces+insulation+large number of elements exceed the capability of 4nec2 software.

          This weekend I have tried another software: the "CST Studio Suite 2014". I modeled & simulated a simple 1/2 wavelength dipole as my first attempt. Being unfamiliar with this software, I am facing difficulty in interpreting & analyzing the results I got. Hope some tutorials, and many hours of practice will improve the situation. Here is a screenshot of my first attempt:

          CST Suite 2014 - Trial - half wavelength dipole.PNG

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          • Originally posted by abcd567 View Post
            Recently when I compared trial run results with simulation results of 8-element cocos, I found that the 4nec2 software gives around 10% error. It seems antennas with surfaces+insulation+large number of elements exceed the capability of 4nec2 software.
            Hi ab cd, I've been doing some research and came across this website http://www.antennex.com. In particular this paper by L B Cebik http://www.antennex.com/w4rnl/col0706/amod101.html which talks about errors in modelling software.
            T-EGUB1

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            • Originally posted by trigger View Post
              Hi ab cd, I've been doing some research and came across this website http://www.antennex.com. In particular this paper by L B Cebik http://www.antennex.com/w4rnl/col0706/amod101.html which talks about errors in modelling software.
              Hi Dave!
              Very informative article by L. B. Cebik. Thanks for sharing.

              Comment


              • @trigger:
                I have found another free of cost software "emGine". I have downloaded and installed it, and quickly browsed. Seems good. Yet to try it.

                Home page & Download:

                http://www.petr-lorenz.com/emgine/

                Comment


                • Originally posted by abcd567 View Post
                  I have been using the 4nec2 software for about a year for antenna modelling & simulation. This software gave very good results for simple wire antennas such as dipoles, franklins & yagis. It also seemed to give good results for cocos.

                  Recently when I compared trial run results with simulation results of 8-element cocos, I found that the 4nec2 software gives around 10% error. It seems antennas with surfaces+insulation+large number of elements exceed the capability of 4nec2 software.

                  This weekend I have tried another software: the "CST Studio Suite 2014". I modeled & simulated a simple 1/2 wavelength dipole as my first attempt. Being unfamiliar with this software, I am facing difficulty in interpreting & analyzing the results I got. Hope some tutorials, and many hours of practice will improve the situation. Here is a screenshot of my first attempt:

                  [ATTACH=CONFIG]5140[/ATTACH]
                  This looks like I would expect a vertical dipole to look, based on what I see in my test chamber.

                  The difference between what you see and what I can test, if someone want's to build a test sample, is that I can provide actual real world results, and if you want to make another unit with a slightly different spacing or wire diameter, etc we can get some comparison tests.

                  Comment


                  • Originally posted by abcd567 View Post
                    Thanks for your offer for support.
                    If you have time, can you please test this very simple & easy to make antenna's performance (Gain, SWR, Radiation pattern etc):
                    post #1224 on page #123 of this thread - "Another Experiment: A 1/2 λ sleeve dipole"
                    I can see what I can do to build one, but if you want to throw one together and UPS it down here, I will throw it in as soon as I can.

                    However, one antenna doesn't always tell us everything, without something to compare to. I would think a basic dipole style antenna would be a good antenna to compare.

                    Comment


                    • Originally posted by zryder94 View Post
                      .......I am in the final stages of constructing an 8 element Co-Co out of LMR-400 50ohm solid center conductor coax. I have seen many different designs posted, so I wanted to see if I can get some consensus on what you guys have found as best practices.

                      At the moment, it is constructed with 8 elements, cut to 1/2 elec WL. I have a 1/4WL stub attached to the top, and the bottom element is directly connected to more LMR-400 for the feedline.

                      Would it be best to add another 1/4 elec WL stub of coax between the "top" element and the 1/4WL stub?

                      What seems to be the best method for adding a sleeve balun, if one is truly needed?........
                      Forum Member 1090MHZ has built a very successful Coco, using Heliax (I think LDF4-50). Please see:

                      (1) His Post# 1320 on page 132 and of this thread.

                      (2) His Post #1326 on Page 133 of this thread.

                      (3) Go directly to his web site where he has posted the design photos: http://ads-b.ca/antenna-collinear-F-CYYZ2/

                      Comment


                      • Originally posted by abcd567 View Post
                        Forum Member 1090MHZ has built a very successful Coco, using Heliax (I think LDF4-50). Please see:

                        (1) His Post# 1320 on page 132 and of this thread.

                        (2) His Post #1326 on Page 133 of this thread.

                        (3) Go directly to his web site where he has posted the design photos: http://ads-b.ca/antenna-collinear-F-CYYZ2/
                        Very interesting stuff. I actually have a bit of the same hardline at the home QTH, if I need to build a replacement for the LMR-400 CoCo, I will try and use that stuff. It isn't long enough to have any other use anyhow.
                        I wonder why he felt it necessary to remove the jacket from the hardline. I wouldn't think the jacket would have any significant impact on VF. Surely you would want to remove some from the ends, but why all the way along the length?

                        Comment


                        • Originally posted by zryder94 View Post
                          Very interesting stuff. I actually have a bit of the same hardline at the home QTH, if I need to build a replacement for the LMR-400 CoCo, I will try and use that stuff. It isn't long enough to have any other use anyhow.
                          You can use his design for you LMR400, but dont use lengths in mm shown in his pictures. You have to calculte your element lengths based on LMR400's Velocity Factor.

                          His design is:
                          8 elements 1/2 wavelength using VF of coax
                          1 element at top 1/4 wavelength using VF of coax, shorted at top.
                          1 whip at top 1/4 wavelength using VF=1
                          1 decoupling sleeve at bottom, 1/4 wavelength using VF=1


                          I wonder why he felt it necessary to remove the jacket from the hardline. I wouldn't think the jacket would have any significant impact on VF. Surely you would want to remove some from the ends, but why all the way along the length?
                          No idea. Only he (member 1090MHz) can reply.
                          Last edited by abcd567; 2014-12-08, 22:42.

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                          • Member jepolch of planefinder forum has posted photo of his Cantenna enclosed in 100 DVD case.
                            The amplifier is right below the case, wrapped in black self amalgamating tape.

                            Roof mount from Amazon.com: http://www.amazon.com/gp/product/B00DJWNYT0




                            The details of the platform on which DVD case/Cantenna is mounted (in words of it's owner & maker):

                            I made the platform out of 1/4 inch birch plywood I had lying around. I traced the bottom of the DVD case and then added some extra space for the shelf bracket. I sprayed the platform with white paint to protect it from the rain.

                            .
                            Last edited by abcd567; 2014-12-09, 00:48.

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                            • Hi!

                              Talk about being new in the forum... I just signed up/registered. This is my very first Post! I've read what I could about the Forum Rules. To read thru the 194pages of this thread on "Best Antenna" is also a bit daunting... plus a lot of the technical details mentioned in the posts is just way above my understanding, for now. I am slowly learning.

                              I would like to experiment with these ADS-B dongles and make measurements on a few sites before I apply to host Flightradar24 equipment. I think it is really needed in our area (near RPVM airport). Here is the dongle I am getting...

                              http://www.ebay.com/itm/USB2-0-Digit...item35d9a8efcd

                              It comes with a generic antenna which I would like to change. From the several antenna designs that have come up in the few pages I have read on this thread, which do you think is "best" for this kind of dongle? Any design with an MCX adapter that fits into the dongle should be fine...

                              I plan to use the same magnetic foot the generic antenna has (on i think RG174) and make a new WIRE-collinear one for it designed for the ADS-B frequency. Would this be "better" on the same RG174 coax? How about the 1/4wave GP antenna? This design looks doable for me too... I intend to do both antennas so I can compare.

                              Any suggestion/help would be appreciated from the veterans on this thread... ;-) Thanks!
                              Last edited by gquejada; 2014-12-09, 14:34.

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