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  • Originally posted by peterhr View Post
    I tried mine with 2 amplifiers - nothing, but it's fine with one.

    More doesn't means it is good.

    In fact, it could saturate the signal, over-drive of the 2nd amplifier and cause less planes to be seen.

    My setup is simple - a high gain Omni Antenna, keep the signal loss to the minimum by using GOOD Quality Feeder and shorter length.

    I almost enter into F-WBGG1 garden territory.

    3 Nov 2013 flight until near Sambas Borneo.jpg
    F-WSSS1 - Cats refused to Pee & Pooh on RadarBox - Running a FR24 Receiver & DVB-T Dongle 24/7 to piss off The Chief Thief.

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    • Originally posted by Birdie View Post
      More doesn't means it is good.

      In fact, it could saturate the signal, over-drive of the 2nd amplifier and cause less planes to be seen.

      My setup is simple - a high gain Omni Antenna, keep the signal loss to the minimum by using GOOD Quality Feeder and shorter length.

      I almost enter into F-WBGG1 garden territory.

      [ATTACH=CONFIG]2853[/ATTACH]
      Caused no planes to be seen! ... I don't think there were enough volts being passed to run the second amp (or it may be faulty).

      The whip style collinear antenna was living up to it's name last night - due to high winds - it's still working so I guess it's still up there.

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      • Originally posted by Birdie View Post
        More doesn't means it is good.

        In fact, it could saturate the signal, over-drive of the 2nd amplifier and cause less planes to be seen.

        My setup is simple - a high gain Omni Antenna, keep the signal loss to the minimum by using GOOD Quality Feeder and shorter length.

        I almost enter into F-WBGG1 garden territory.

        [ATTACH=CONFIG]2853[/ATTACH]
        That's what I always recommend too... a good antenna, good antenna height, and the best coax you can get. Using amp's is not necessary at all if you do it right. These cheap satellite amp's are not designed for the purpose of ADS-B. They are broadband amplifiers designed to be used in conjunction with a stacked satellite LNB. Because of this they expect to see an input signal, provided by the LNB, that has the same gain over the entire 900 - 2500 MHz. Now if you use this same amp with an off air antenna, ADS-B setup, you only need to boost the one frequency of 1090 MHz, however it's going to see everything on the air from 900 - 2500MHz and will try to amplify it all. A strong signal from say a cell tower near by at 1900MHz will saturate the amp... This will result in poor performance at 1090MHz. This is also why using an amp seems to be a hit and miss with many people. What you want, if you have to use an amp, is a band pass filter... like this one... placed in front of the amp: http://www.minicircuits.com/npa/CBP-1034C+_NPA.pdf

        Or this one: http://www.minicircuits.com/pdfs/VBFZ-1065+.pdf



        Where you located Birdie ?
        Last edited by 1090 MHz; 2013-11-03, 07:08.
        www.ADS-B.ca

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        • Originally posted by 1090 MHz View Post
          That's what I always recommend too... a good antenna, good antenna height, and the best coax you can get. Using amp's is not necessary at all if you do it right. These cheap satellite amp's are not designed for the purpose of ADS-B. They are broadband amplifiers designed to be used in conjunction with a stacked satellite LNB. Because of this they expect to see an input signal, provided by the LNB, that has the same gain over the entire 900 - 2500 MHz. Now if you use this same amp with an off air antenna, ADS-B setup, you only need to boost the one frequency of 1090 MHz, however it's going to see everything on the air from 900 - 2500MHz and will try to amplify it all. A strong signal from say a cell tower near by at 1900MHz will saturate the amp... This will result in poor performance at 1090MHz. This is also why using an amp seems to be a hit and miss with many people. What you want, if you have to use an amp, is a band pass filter... like this one... placed in front of the amp: http://www.minicircuits.com/npa/CBP-1034C+_NPA.pdf

          Or this one: http://www.minicircuits.com/pdfs/VBFZ-1065+.pdf
          (1)Based on 1090MHz's posts, I am planning to install the ADSB Software on my laptop, place the laptop very close to where my indoor antenna is installed, and hookup using a short piece of coax,WITHOUT any Amplifier, and compare the results with what I am getting with current setup (long low quality coax+2 amps).

          (2) If there is a strong Cellular or other signal in the location, rather than using a band-pass filter, it is better to use a single frequency tuner for 1090 MHz between antenna and amplifier. This is similar to FM Radio, which receive only one station at a time (to which the radio is tuned), and reject all others. This tuner can be a simple LC Tuned circuit (a coil & a capacitor), or a coil with Self Resonant Frequency (SRF) of 1090 put across core & shield of coax before the Amplifier, and will short-circuit all frequencies (including cellular) except 1090 MHz +/- few MHz (i.e. a narrow band of frequencies centered at 1090 MHz).
          Last edited by abcd567; 2013-11-03, 15:44.

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          • I wonder which antenna has a higher gain: a 1/4-wavelength groundplane antenna or perhaps a 8-section collinear. I am thinking about making such an antenna and test it against the gp antenna.

            I ask for advices on making such an antenna using RGC-58 cable as the collinear elements. I already use RGC-213 as the downfeed (antena >> dongle) cable.

            Any insights will be welcome.

            Ricardo
            SBFI / Brazil


            Enviado do meu iPad usando o Tapatalk

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            • I made this antena http://www.balarad.net/ with regular tv coax cable, the cheapest one, and its...ok.
              Waitnin' for LMR -400 to make new one and see improvment....should be much better.
              For official support use Contact Form

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              • Amper,

                Do check the resistance/impedance on the LMR400 and make sure it matches. We get best results from 75Ohm cable (presumably the dongle is 75Ohm as well)... I think the LMR400 is 50Ohm. In that case you need to make sure of your resistor at the top.
                Just my 2cents....

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                • i read somwhere on the forum that it's best to use LMR-400
                  do you have any other sugestion?
                  afterall, i am a newbie
                  For official support use Contact Form

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                  • Originally posted by Amper View Post
                    i read somwhere on the forum that it's best to use LMR-400
                    do you have any other sugestion?
                    afterall, i am a newbie
                    LMR-400 is the best cable to use because of it's low loss properties. Most all radio equipment is 50 ohm impedance including the FR24 receivers. Impedance matching is most critical when transmitting a signal then just receiving.

                    The dongle was designed for ATSC TV reception, and TV antennas are 75 ohm impedance... so the dongle will be 75 ohm. If HermanZA says 75 ohm works better then 50 ohm with the dongle then this is most likely the reason why.
                    www.ADS-B.ca

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                    • what 75 Ohm cable do you sugest for best preformance
                      For official support use Contact Form

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                      • I build one with LMR also, assumed it would be better... installed it and it had terrible reception. One of the forum members pointed out that I have a cable mismatch. 50Ohm antenna, with a little piece of 75Ohm feeder. And BANG! you mess up what you thought you will gain with the LMR

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                        • Originally posted by Amper View Post
                          what 75 Ohm cable do you sugest for best preformance
                          F5ANN uses them for his ADS-B testings. You can check it here: http://groups.yahoo.com/neo/groups/M...ns/topics/1580

                          hope this helps.

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                          • Originally posted by Amper View Post
                            what 75 Ohm cable do you sugest for best preformance
                            Cable TV systems use all 75 ohm cables ... RG6, RG11, and HardLine QR540, QR715, QR860, QR1125.

                            http://en.wikipedia.org/wiki/Coaxial_cable
                            www.ADS-B.ca

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                            • I have run two trials of coverage:
                              (1) No in-Line amplifier.
                              (2) With in-Line amplifier
                              Both trial setups were with very short length of coaxial cable
                              .

                              Test Setup
                              (1) Antenna: 75 ohm quarter-wave dipole (each leg 6.8 cm, total height 13.6 cm).
                              (2) Receiver: DVB-T USB Dongle, 75 ohm input impedance.
                              (3) Coax cable between antenna & receiver: 75 ohm RG6 - Very short length (11 feet / 3.5 meters).
                              (4) In-Line Amplifier RCA D903 (13-18dB, 950 to 2050 MHz)

                              There is a vast difference between ranges with & without in-Line amplifier.

                              Please see two (2) sets of photos below.


                              Test 1 - No Amplifier
                              coverage-quarterwave-dipole-without-amplifier.gif DSC02788R.jpg DSC02785R1.jpg DSC02784R.jpg
                              Last edited by abcd567; 2013-11-09, 09:04.

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                              • Test 2 - WITH Amplifier
                                coverage-quarterwave-dipole-WITH-amplifier.gif DSC02793R.jpg DSC02792R1.jpg DSC02794R.jpg
                                Last edited by abcd567; 2013-11-09, 08:58.

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