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  • Due to yesterday's abnormal graph, I checked my system and found a defective (dodgy/intermittent) connector. I replaced the connector and repeated yesterday's test, and results are now normal as follows.

    1) When The λ whip was replaced by Franklin whip, there was a distinct drop in performance to about 40%.

    2) When crude impedance matching was added to the Franklin Spider, there was a distinct increase in performance, jumping up from 40% to 85% of Spider.

    Now I have to optimize the matching network by:

    1) Using an adjustable trimmer capacitor 2 - 5 pF instead of fixed ceramic capacitor of 2 pF.

    AND

    2) Try three lengths of transmission lines (i.e 205 mm, 210 mm & 215 mm) between antenna & capacitor.

    I hope I will be able to achieve optimum matching, in which case the Franklin Spider's performance will (hopefully) exceed Spider's performance.




    .
    Last edited by abcd567; 2015-07-19, 02:44.

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    • I made also this Franklin Spider antenna today. Lets see how it performs. And thanks abcd567 at good antenna tips
      F-EFRO3

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      • Originally posted by AzKo View Post
        I made also this Franklin Spider antenna today. Lets see how it performs. And thanks abcd567 at good antenna tips
        The Franklin Spider is inferior to Spider if impedance matching is not used, but can be made superior to it by impedance matching, as shown in above post.

        Today I have tried two tweaks in values of the two parameters of impedance matching as below:

        (1) Soldered a third 1 pF Capacitor in parallel with existing two, increasing the total value of Capacitor from 2 pF to 3 pF

        (2) Tried two different lengths of transmission line between the Antenna & the Capacitor. Original was 210 mm (including length of connectors at both ends). I made two more, one 225 mm (including length of connectors at both ends), other 240 mm (including length of connectors at both ends).

        The combination of 3 pF Capacitor & 240 mm Transmission Line (including length of connectors at both ends) between Capacitor & Antenna resulted in Franklin Spider surpassing the performance of Spider.

        Since each built of DIY antenna is slightly different, these values (240 mm / 3 pF) may not be optimum for every one, but sure will be close to optimum, provided RG6 Coax cable (with VF 0.83 to 0.85) is used as transmission line piece between Antenna & Capacitor, shown in photo in my post #2395.
        Last edited by abcd567; 2015-07-20, 01:29.

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        • This is my 2nd quarter wave antenna with 8 legs, new build have not install yet , first one is on duty .
          IMG_5535.jpg

          Another antenna I made month ago , it prove my solder skill pretty bad .
          IMG_5463.jpg
          T-ZSSS32 F-ZSSS1 force shutdown by local regulation

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          • Trial Runs for Comparison of FRANKLIN SPIDER (With Impedance Matching added), Spider, and Franklin Spider.


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            • Originally posted by iamnothere View Post
              This is my 2nd quarter wave antenna with 8 legs, new build have not install yet , first one is on duty .
              [ATTACH=CONFIG]6262[/ATTACH]

              Another antenna I made month ago , it prove my solder skill pretty bad .
              [ATTACH=CONFIG]6263[/ATTACH]
              Well done! Keep experimenting. That is how you are going to learn & find the best antenna built for your system. Dont worry about soldering. Many of us (including me) have worst soldering skill than your's.

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              • Build spider today when finally get some stuff to build something. And im not also so good solder. But main thing is that antenna is working

                2015-07-20 22.39.17.jpg
                F-EFRO3

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                • Originally posted by AzKo View Post
                  Build spider today when finally get some stuff to build something. And im not also so good solder. But main thing is that antenna is working

                  [ATTACH=CONFIG]6265[/ATTACH]
                  Good work!

                  Spider is one of the easiest and very reliable antenna for begginners. In fact all antennas with a wavelength (69mm) whip and a groundplane (metal disc, horizontal radials, slanting radials, or a food/drink can, also known as Cantenna) are ideal for beginners.

                  The reasons are:

                  (1) These antennas are naturally resonant, i.e. have an impedance close to 75 ohms, which matches with the Coaxial cable, Amplifier & Receiver (dvb-t) impedance and gives a swr less than 1.5, a highly desireable situation.

                  (2) These antennas have high dimensional tolerance, so few mm error in length of whip or radials or few degrees error in bending down the radials does not appreciably degrade its performance.

                  Dont worry about soldering. The antenna works good even if the soldering is not very good.

                  Please click the link below to see 4 different antennas, all with wavelength whip, but each with different methods of providing groundplane.


                  http://forum.flightradar24.com/threa...-FOR-BEGINNERS
                  Last edited by abcd567; 2015-07-20, 23:38.

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                  • Thanks , abcd567
                    T-ZSSS32 F-ZSSS1 force shutdown by local regulation

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                    • Look what I caught on my receiver:
                      A Crazy Pilot Taxiing Under Influence of Alcohol?
                      No it is an airport maintenance vehicle fitted with ADS-B transponder!


                      Last edited by abcd567; 2015-07-22, 07:15.

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                      • Indeed, it's a maintenance vehicle -> http://ightwww.flightradar24.com/data/airplanes/mtc25/

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                        • On a slight deviation from the topic, but semi-related .... :-)

                          abcd567 - what are you using to generate the graphs in post #2402 ??

                          Cheers.
                          T-YSBK22

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                          • Originally posted by rodeo View Post
                            On a slight deviation from the topic, but semi-related .... :-)

                            abcd567 - what are you using to generate the graphs in post #2402 ??

                            Cheers.
                            These curves are generated on Raspberry Pi, using "RRD Tools Collectd" - original work by @obj: (Oliver Jowett), and automated installation script by @Xforce30164:

                            For the tool to work, in your RPi, you have to first replace dump1090 (Malcom Robson) with dump1090-mutability (Oliver Jowett), then install the "rrd tools "collectd", either directly (difficult) or using script by xforce30164 (easy).

                            My DVB-T is connected to a Raspberry Pi. The RPi has Raspbian Wheezy Operating System, dump1090-mutability decoder/receiver, and FR24, Planefinder, and Flightaware data feeders installed. In addition I have installed "rd tools collectd".




                            To make it easy for you, here is the code;

                            (1) To install dump1090-mutability see the code here: DUMP1090-MUTABILITY (for advance users)


                            (2) To install the "rrd tools collectd" using automated script by xforce30164:

                            Code:
                            cd ~
                            sudo apt-get install rrdtool && sudo apt-get install collectd
                            wget http://raspi.ayadex.com/volatile/web_install.sh
                            sudo chmod +x web_install.sh
                            sudo ./web_install.sh "dump-tools"
                            cd dump-tools
                            sudo ./install.sh "crontab"
                            
                            # First attempt of  sudo ./install.sh "crontab" may show failure. Repeat the command, and it will show crontab installed.
                            
                            sudo reboot

                            To see the graphs:
                            (1) In RPi browser - type in your browser http://localhost/collectd or http://127.0.0.1/collectd

                            (2) In Desktop/Laptop browser on the same network type http://<ip address of RPi on local network>/collectd. The IP address of RPi can be found from router setup page and will be something like 192.68.2.15

                            Please take care while typing "collectd". There is no e between t & d.


                            For further details, please see these links:

                            (1) dump1090 Collectd graphs and automated Installation script - by xforce30164

                            (2) Flightaware Forum - System Monitoring

                            (3) Planefinder Forum - Web Portal and Collectd/rrd graphs automated installation

                            (4) RRD Tool - Original Author Tobi Oetiker - 1999

                            (5) Collectd - Original Author Florian Forster - 2005
                            Last edited by abcd567; 2015-07-22, 19:47.

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                            • And spider is working. First time i see my radar in FR24

                              nimet&amp;#246;n.png
                              F-EFRO3

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                              • Originally posted by AzKo View Post
                                And spider is working. First time i see my radar in FR24

                                [ATTACH=CONFIG]6267[/ATTACH]
                                ONNEKSI OLKOON
                                CONGRATULATIONS!

                                Wow, you live near Rovaniemi Airport, which is at Arctic Cirle! I felt Toronto is very cold, but it is no comparison to your place!

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