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  • Originally posted by Rooster View Post
    do you have a link to the Franklin antenna please ?
    3rd Link. Download pdf. See page 20 for Franklin
    http://www.146970.com/PDFs/Antenna%2...na%20Ideas.pdf

    Sent from my N762 using Tapatalk 2

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    • Originally posted by abcd567 View Post
      Do not adjust rtl1090 frequency. There is nothing wrong with rtl1090. This is ERROR in SDR# DISPLAYED FREQ vs ACTUAL FREQ.
      Have you tried another software "ADSB#" as an alternate to "RTL1090"?

      Sent from my N762 using Tapatalk 2
      Ok So then why do I also need to adjust the freq in DUMP1090 also if it's only an SDR# problem. By not offsetting the freq I get less distance and amount of aircraft I receive. I stated over and over again that auto gain settings don't work for me. More than likely (I'm guessing) My antenna is not tuned to exactly 1090 which is an error on my part since I have no way of tuning my antenna segments or length. My collinear segments are 116 mm each. Is that right? I don't know other than a best guess. Manually setting my freq gets me out to 350 miles in some directions but not all. Not adjusting it gives me 211 miles. This isn't one test but over and over and over till I get the best possible distance and amount of A/C I pick up. For me... I'm certain my weather proofing around my collinear is causing the freq off set. I also never said anything was wrong with RTL. I know it's tuned to 1090 mhz. It doesn't know my tuner is not dead on. Maybe my SDR tuners are off. All of them but able to compensate for my off freq's.
      Andy T-KTIK1

      RPI - http://Temporarily off Line due to t...98.37.214:8080

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      • Originally posted by Rooster View Post
        do you have a link to the Franklin antenna please ?
        http://forum.planefinder.net/threads...iy-antenna.23/

        Sent from my N762 using Tapatalk 2

        Comment


        • Hi guys,
          Is the velocity factor of a cable frequency dependent?
          What is velocity factor of LMR400 at about ADS-B frequency?

          Comment


          • LMR400 had a VF 0.85 and is independent of frequency...

            Sent using Tapatalk from my ZX81

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            • COMPARISON OF COVERAGE OF FOUR (4) DIFFERENT ANTENNAS
              WITHOUT AMPLIFIER
              VERY SHORT COAXIAL CABLE (11 FEET / 3.5 METERS) BETWEEN ANTENNA & RECEIVER



              1) DIPOLE: 1/2 WAVELENGTH
              Dipole-halfwave.jpg

              2) FRANKLIN DIPOLE: 1/2-OVER-1/2 WAVELENGTH
              Franklin Dipole-half-over-half wavelength.jpg

              3) COAXIAL COLLINEAR: 3-AND-1/2 ELEMENTS (EACH ELEMENT 1/2 WAVELENGTH) WITH SHORTED TOP
              CoCo-3-and-half+shorted-top.jpg

              4) COAXIAL COLLINEAR: 3-AND-1/2 ELEMENTS (EACH ELEMENT 1/2 WAVELENGTH) + 1/4 WAVELENGTH WHIP
              CoCo-3-and-half+quarter-whip.jpg


              Coaxial Collinear 1/2 wave element =1/2 x wavelength @ 1090 MHz x coaxial cable velocity factor
              For RG6 cable with FPE (Foamed PolyEthylene) insulation, velocity factor = 0.8
              Coaxial 1/2 wave element =1/2 x 27.5 cm x 0.8 = 11 cm


              Tests for these antennas WITH Amplifier will be posted when completed.


              .
              Last edited by abcd567; 2013-12-01, 22:03.

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              • Originally posted by peterhr View Post
                Hi guys,
                Is the velocity factor of a cable frequency dependent?
                What is velocity factor of LMR400 at about ADS-B frequency?
                LMR400 has a velocity factor of between .80 and .85 depending on manufacture. Need to see product specs for each company. Am sure you already know LMR400 is 50 ohm's. To be honest I don't know about freq dependent but I do know that LMR400 has less signal loss over longer distance.
                Andy T-KTIK1

                RPI - http://Temporarily off Line due to t...98.37.214:8080

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                • To: abcd567

                  Very impressed. Nice work. Much appreciated.
                  Andy T-KTIK1

                  RPI - http://Temporarily off Line due to t...98.37.214:8080

                  Comment


                  • Less than what?
                    I think we are getting tied up in technical mumbo jumbo a little here.. The antenna location is the most important factor (including your house!)
                    I am in the Midlands, UK... And I can see aircraft near the Irish coast... The Scandinavian coast, the edge of Scotland and down to Devon... All with a 10 dongle and 10 element coco fed with 15 metres of satellite cable, at gutter height!

                    Sent using Tapatalk from my ZX81

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                    • Originally posted by abcd567 View Post
                      Congratulations.
                      Welcome to CYYZ ADS-B Radar community.

                      Sure you are going to get a great coverage with FR24 supplied Antenna mounted on the 150 feet high tower, and the Low Attenuation Coaxial cable LMR400/RG8 which you will use to hook-up antenna to receiver.
                      I am waiting eagerly to see your results.

                      I am not using equipment supplied by FR24.
                      Instead, I am using my own low cost equipment, much of which, including antenna, is home-brewed, and the antenna is located indoors. Even then I am getting a reasonably good coverage. Please see attached pictures of my setup:

                      Picture 1: Coverage Map - CYYZ area
                      Picture 2: 4-Element Franklin Co-Linear Dipole Antenna - Home Brewed - Located Indoors.
                      Picture 3: in-Line Amplifier & Bias-T (DC Power Injector) - Home-Brewed.
                      Picture 4: DVB-T SDR USB Receiver connected to Desktop Computer.
                      Picture 5: Schematic Diagram of my Setup.

                      [ATTACH=CONFIG]2666[/ATTACH] [ATTACH=CONFIG]2667[/ATTACH] [ATTACH=CONFIG]2668[/ATTACH] [ATTACH=CONFIG]2669[/ATTACH] [ATTACH=CONFIG]2670[/ATTACH]
                      Hi, With regards your Antenna
                      It looks like two coax cables are joined into one F-connector? How did you do this? I'm waiting on my dongle and am looking into home made Antenna options.

                      Mike

                      Comment


                      • Originally posted by peterhr View Post
                        Hi guys,
                        Is the velocity factor of a cable frequency dependent?
                        What is velocity factor of LMR400 at about ADS-B frequency?
                        Originally posted by andyk1 View Post
                        LMR400 has a velocity factor of between .80 and .85 depending on manufacture. Need to see product specs for each company. Am sure you already know LMR400 is 50 ohm's. To be honest I don't know about freq dependent but I do know that LMR400 has less signal loss over longer distance.
                        The Impedance & Velocity factor are NOT frequency dependent.

                        Velocity factor is mainly dependent on Dielectric (Core Insulation Material).

                        Most of LMR400 manufacturers use Foamed Polyethylene and specify 0.85 Velocity factor.

                        Average values of VF are given below. For exact values, refer to Cable Manufacturer's Data Sheets.

                        VF for solid polyethylene (PE) is about 0.66
                        VF for foam polyethylene (FPE) is about 0.78 to 0.88
                        VF for air is about 1.00
                        VF for solid polytetrafluoroethylene (PTFE) is about 0.70
                        VF for foam polytetrafluoroethylene (FPTFE) is about 0.84

                        Attenuation (Loss) per meter is dependent on frequency, and increases with increasing frequency.

                        For LMR400, attenuation at 30 MHz is 2.2 dB/100 meters, at 900 MHz it is 12.8 dB/100 meters, and at 2500 MHz it is 22 dB/100 meter.

                        The Velocity Factor (VF) is determined by the permeability and permittivity of the Dielectric.
                        VF = 1/{square root of (relative permeability of dielectric x relative permittivity of dielectric)}
                        where relative means value for dielectric compred to value for vacuum.

                        Velocity factor of Vacuum is EXACTLY 1.00000000000000000000......
                        Velocity factor of Air is APPROXIMATELY 1.0 .....

                        .
                        Last edited by abcd567; 2013-12-02, 16:11.

                        Comment


                        • Originally posted by mickopla View Post
                          Hi, With regards your Antenna
                          It looks like two coax cables are joined into one F-connector? How did you do this? I'm waiting on my dongle and am looking into home made Antenna options.
                          Mike
                          It is ONE coax + an extra core-only, inserted into shield/braid of coaxial cable.
                          See the pictures below. The "Enlarged View" rectangle at top-left of picture 3 gives answer to your question.

                          Are you going to use in-Line Amplifier? If not, Franklin without Amplifier is hopeless because of it's high impedance. With in-Line Amplifier it gives good results.

                          Try half-wave Dipole also. It is simplest and shortest (2 legs, one up one down, each 6.8 cm) and has an impedance of 75 ohms which matches with impedance of coaxial cable and the Dongle. See my yesterday's post above for comparison of various antenna WITHOUT Amplifier.

                          The DVB-T USB Dongle's built-in pre-Amplifier is not powerful enough for ADS-B, as it is designed for Local TV reception, where signals are strong. Adding an in-Line Amplifier greatly improves Range.

                          Antenna-Franklin-Assembly-Steps-1.jpg Antenna-Franklin-Assembly-Steps-2.jpg Antenna-Franklin-Assembly-Steps-3.jpg Antenna-Franklin-Assembly-Steps-4.jpg DSC02576-R90c.jpg
                          Last edited by abcd567; 2013-12-02, 01:21.

                          Comment


                          • Originally posted by abcd567 View Post
                            It is ONE coax + an extra core-only, inserted into shield/braid of coaxial cable.
                            See the pictures below. The "Enlarged View" rectangle at top-left of picture 3 gives answer to your question.

                            Are you going to use in-Line Amplifier? If not, Franklin without Amplifier is hopeless because of it's high impedance. With in-Line Amplifier it gives good results.

                            Try half-wave Dipole also. It is simplest and shortest (2 legs, one up one down, each 6.8 cm) and has an impedance of 75 ohms which matches with impedance of coaxial cable and the Dongle. See my yesterday's post above for comparison of various antenna WITHOUT Amplifier.

                            The DVB-T USB Dongle's built-in pre-Amplifier is not powerful enough for ADS-B, as it is designed for Local TV reception, where signals are strong. Adding an in-Line Amplifier greatly improves Range.

                            [ATTACH=CONFIG]3006[/ATTACH] [ATTACH=CONFIG]3007[/ATTACH] [ATTACH=CONFIG]3009[/ATTACH] [ATTACH=CONFIG]3008[/ATTACH] [ATTACH=CONFIG]3010[/ATTACH]
                            Thanks for the advice. Very much appreciated. I'm open to all types of Antenna and have already made the collinear antenna which is mentioned on this thread. I have ordered an in line amp to increase my options.
                            All the houses around me are two storey high so there are no big obstructions that would block the signal. I'm toying with the idea of an attic install or outside at roof height. Would there be a big percentage loss level having the Antenna indoors in my attic rather than outside? The Antenna height would be more or less the same.

                            Mike

                            Comment


                            • Originally posted by mickopla View Post
                              Thanks for the advice. Very much appreciated. I'm open to all types of Antenna and have already made the collinear antenna which is mentioned on this thread. I have ordered an in line amp to increase my options.
                              All the houses around me are two storey high so there are no big obstructions that would block the signal. I'm toying with the idea of an attic install or outside at roof height. Would there be a big percentage loss level having the Antenna indoors in my attic rather than outside? The Antenna height would be more or less the same.

                              Mike
                              I'd stick it outside if possible - I posted some plots a little way back in this thread that show the sharp range cutoff from 300km to 50km cause where my antenna falls in the 'shadow' of the next door neighbours roof. One I get some new downfeed and time on a nice day to do it - I'll be lifting my mast by another 1.5m section. (I have wall mounted T & K brackets, holding 2 sections of Sectional Aluminium 20' Pole Mast Set - 4 x 5ft Swaged Pole Sections Slot 1.25" OD (32mm Diameter) - bought from Delcom Systems Ltd)

                              Comment


                              • Originally posted by mickopla View Post
                                .....All the houses around me are two storey high so there are no big obstructions that would block the signal. I'm toying with the idea of an attic install or outside at roof height. Would there be a big percentage loss level having the Antenna indoors in my attic rather than outside? The Antenna height would be more or less the same.
                                Mike

                                Originally posted by peterhr View Post
                                I'd stick it outside if possible - I posted some plots a little way back in this thread that show the sharp range cutoff from 300km to 50km cause where my antenna falls in the 'shadow' of the next door neighbours roof.....
                                I agree with peterhr. At ADS-B frequency, the transmission between transmitting and recieving antennas is 'line of sight'. If the antenna is above the level of neighbour's roof, it can 'see' the horizon, like you can see horizon if your eyes are above the level of neighbour's roof. In all those direction in which the antenna can "see" the horizon, it gets maximum coverage. In all those directions in which antenna falls in the "shadow" of neighbour's roof and cannot "see" the horizon, range will be sharply cut-off.

                                If you look at my coverage plots posted two days ago, you will notice sharp drops in coverage in many directions. These are caused by buildings higher than my antenna. My antenna therefore can not "see" horizon in those directions, and a sharp drop in range resulted. I live in an apartment, and building management does not permit installation of individual antennas on roof of the building. I am restricted to locate my antenna indoor near windows.

                                Sent from my N762 using Tapatalk 2
                                Last edited by abcd567; 2013-12-02, 16:34.

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