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  • Originally posted by HermanZA View Post
    ABCD, You come across as quite a clued up radio amateur, or someone who works with signals and propagation? .......
    Wow, the link you gave ( http://www.heywhatsthat.com/main-090...?view=ML2O2PSQ) is great.
    Thanks for sharing.

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    • Originally posted by HermanZA View Post
      [snip]This link also muchly shows what you are saying. http://www.heywhatsthat.com/main-090...?view=ML2O2PSQ Create new panorama, enter your coordinates, receiver height, let it plot... then on the map, select: Up in the air.
      With my little knowledge I had a month ago, that plot gave me a prediction as close as what I am getting at present. Can also set your AC min and max height, then it shows your reception based on that.
      This is something Mike should look at to help decide when placing FR24 receivers.

      I have trees to the north of me at 50 feet - yet I still getting 200kms range there, and clear skies to the SE and only about 100km - the google KML plot from this site shows that my LOS to the SE to a 'remote height' of 25000 feet is about 1km and explains that once I get my antenna above the roof peaks it will even out the plot a little but my view to the SE will still be crap in comparison.

      The trees have less blocking effect than the in-perceptible surrounding low hills.

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      • It would be interesting if some of you can use that link to plot your sites prediction and then also show your actual coverage. Think I'll start a new thread (a bit later today) and post mine, and hopefully others will do the same. It would be interesting to see the prediction vs real coverage. Might just help us lot in seeing where we can better our coverage by some means or another.

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        • Originally posted by abcd567 View Post
          Wow, the link you gave ( http://www.heywhatsthat.com/main-090...?view=ML2O2PSQ) is great.
          Thanks for sharing.
          Unfortunately it's designed for wireless ISP planning... which is point-to-point short range links. The program would not allow me to do anything over 100 miles. Has anyone figured a way around this limit?

          I did come across this program that is a plugin for Google Earth ... there is a small Pay Per Use user cost.... but it looks very promising. https://cloudrf.com/Keyhole_Radio
          Last edited by 1090 MHz; 2013-09-28, 10:52.
          www.ADS-B.ca

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          • Now what did I do wrong here? New antenna made up of 14 elements of LMR400 cable, feeding down with RG6. Velocity factor is the same for both cables, cable runs and antenna height are the same, yet the new antenna gives poorer coverage than the old. New one was tested for shorts and its clean. Also open ended (no resister).

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            • Originally posted by 1090 MHz View Post
              Unfortunately it's designed for wireless ISP planning... which is point-to-point short range links.
              But it can also do a prediction for up in the sky coverage - just enter the correct parameters.
              up-in-the-air.jpg

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              • Originally posted by HermanZA View Post
                Now what did I do wrong here? New antenna made up of 14 elements of LMR400 cable, feeding down with RG6. Velocity factor is the same for both cables, cable runs and antenna height are the same, yet the new antenna gives poorer coverage than the old. New one was tested for shorts and its clean. Also open ended (no resister).
                Is it a Co-linear antenna? If yes the more elements less opening angel. Most planes are above. Some days ago someone posted a picture that shows that (now I cant find it).
                LMR400 is 50 ohm, RG6 is 75 ohm it can do signal loos.

                Poul
                T-EKCH5: Raspberry Pi 4-B (Buster) + FlightAware Pro Stick Plus + FlightAware 1090MHz Bandpass Filter Dark Blue + A3-ADS-B Antenna

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                • Poul, THANKS!!! I forgot about that. Did write down all the specs, and noted that difference. Guess thats why I wanted to install the resistor, but through the build decided to keep this one the same as the previous one, so I could compare the change between 8 and 14 elements, without any other differentials. Thanks for pointing me to my mistake.
                  ...let me now get back to building another antenna with just RG6!

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                  • My 10 / 11 element collinear was inside a 21.5mm white plastic overflow pipe, so while I had the 5' steel mast down to replace it with a 10' aluminium mast (to get the antenna over roof height), I slipped a length of tight fitting pipe over it in an effort to stiffen it. so it doesn't stir so much in the breeze.

                    I don't think I gained anything.

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                    • Originally posted by HermanZA View Post
                      Now what did I do wrong here? New antenna made up of 14 elements of LMR400 cable, feeding down with RG6. Velocity factor is the same for both cables, cable runs and antenna height are the same, yet the new antenna gives poorer coverage than the old. New one was tested for shorts and its clean. Also open ended (no resister).
                      The first Antenna I tried was CoCo (Coaxial Collinear), but it gave me poor results. So I decided to go for wire antennas. I started with A 1/2 wavelength Dipole which is the tiniest tuned antenna. At 1090 MHz, it had a total height of 13.6 cm. When I started, I did not expect good results, but to my surprise, this 13.6 cm tall antenna gave far better results than the 70 cm tall CoCo. I then proceeded to built the 4-Element Franklin Collinear Antenna. It is 54 cm tall (4 times the tiny cute 1/2 wave dipole) but gave excellent results. I have earlier posted the pictures of both these antennas and my coverage on this forum.

                      I suggest you try to built 4 or 6 Element Franklin Co-Linear. I don't recommend 8 element, as increasing the elements increases gain, but narrows the angle of coverage.

                      I am attaching an image which shows two versions. The straight stub & wrap around stub. All the dimensions of both are same, but in wrap around version, the stub is wrapped in a circular shape, to make the antenna fit in a narrower PVC pipe, if required. Otherwise it can be left staraight as shown in alternative 1 in the attached image.

                      This antenna is easier than the CoCo to built. Give it a try and I hope you will get better results than the new & old CoCos.
                      Dipole: Basic 1/2 wave - Theoretical Gain = 2 dBi
                      Dipole: 4-Element 1/2 wave Franklin Colinear - Theoretical Gain = 5 dBi
                      Dipole: 6-Element 1/2 wave Franklin Colinear - Theoretical Gain = 8 dBi
                      Franklin-Wrapped-Stub.png

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                      • ABCD, need to check with you again.
                        On post #80 you said the outer is not used for elements. On the graphic you uploaded, it shows the outer is used (for the bottom segment of elements).
                        Also, when marking off the segments for bending: the 1/4 wave segments, is it a 1/4 wave that you fold in two ... or is it a half wave that your fold in 2? Sketch shows 6.8cm (on the one segment).
                        Sorry if I'm perhaps misunderstanding something, but please just clarify for me.
                        And also a big thank you for sharing all your knowledge and information with us lot, who are still trying to build a good antenna!
                        Last edited by HermanZA; 2013-09-29, 14:42.

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                        • The nice thing about the franklin is that the velocity factor need not be taken into account - get that wrong on a coco and the nice flat signal acceptance disk becomes a cone of maximum sensitivity going up or going down.

                          The franklin can be made on - say - a 22mm PVC tube with wrap around stubs, then popped into bigger tube with a T connector in the centre if it's going outside ... so the wind doesn't mangle it

                          Do you think a Balun at the point the coax is connected would help?

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                          • Originally posted by HermanZA View Post
                            ABCD, need to check with you again.
                            On post #80 you said the outer is not used for elements. On the graphic you uploaded, it shows the outer is used (for the bottom segment of elements).
                            Also, when marking off the segments for bending: the 1/4 wave segments, is it a 1/4 wave that you fold in two ... or is it a half wave that your fold in 2? Sketch shows 6.8cm (on the one segment).
                            Sorry if I'm perhaps misunderstanding something, but please just clarify for me.
                            And also a big thank you for sharing all your knowledge and information with us lot, who are still trying to build a good antenna!
                            The antenna I have built, has both legs of dipole made of coax inner conductor+insulation, but this is not necessary. You can make both legs from thick copper or aluminum wire or tube.

                            The antenna legs are connected to the Feed coaxial cable in following manner:
                            Upper vertical leg of Dipole is continuation of the central conductor of Feed coaxial cable
                            Lower vertical leg of Dipole is connected to the Braid/Shield of the Feed coaxial cable.

                            Please see attached sketch. I wanted to attach close up camera picture of the steps of construction, but did not find time. I will do it shortly.
                            http://imageshack.com/a/img405/4527/evtm.png

                            Antenna-Coax-Dipole-Short-Legs-2.jpg
                            Last edited by abcd567; 2013-09-30, 15:55.

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                            • Originally posted by HermanZA View Post
                              ABCD, need to check with you again.........
                              Please see 4 pictures of antenna assembly steps below:

                              Antenna-Franklin-Assembly-Steps-1.jpg Antenna-Franklin-Assembly-Steps-2.jpg Antenna-Franklin-Assembly-Steps-3.jpg Antenna-Franklin-Assembly-Steps-4.jpg
                              Last edited by abcd567; 2013-09-30, 20:40.

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                              • Originally posted by abcd567 View Post
                                Please see 4 pictures of antenna assembly steps below:

                                [ATTACH=CONFIG]2695[/ATTACH] [ATTACH=CONFIG]2696[/ATTACH] [ATTACH=CONFIG]2697[/ATTACH] [ATTACH=CONFIG]2698[/ATTACH]
                                The attachments seem to be missing.... Invalid Attachment specified. If you followed a valid link, please notify the administrator

                                [UPDATE] OK seems to be working now.
                                Last edited by 1090 MHz; 2013-09-30, 20:44.
                                www.ADS-B.ca

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