Announcement

Collapse
No announcement yet.

best antenna

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Originally posted by abcd567 View Post
    Comparison of simulation results shows that 7.5 element shorted top is slightly better than 8 element open top. Please see screenshots below.

    SCREENSHOT 1 of 2 - Seven-and-Half (7.5) Element CoCo - SHORTED TOP
    Gain = 9.23 dBi, SWR = 3.87 (mismatch loss = 1.85 dB)
    Net Gain Seen by Receiver = Antenna Gain - Mismatch Loss = 9.23 - 1.85 = 7.38 dBi

    [ATTACH=CONFIG]3898[/ATTACH]


    SCREENSHOT 2 of 2 - Eight (8) Element CoCo - Open Top
    Gain = 9.52 dBi, SWR = 4.63 (mismatch loss = 2.33 dB)
    Net Gain Seen by Receiver = Antenna Gain - Mismatch Loss = 9.52 - 2.33 = 7.19 dBi

    [ATTACH=CONFIG]3899[/ATTACH]


    .
    Good work.

    ...so, if the user wants to use 'Satellite lead' amplifier that requires power up the cable (like one of these http://goo.gl/zDcQiW, with power inserter http://goo.gl/r1YRnx and suitable power supply ) then they might be better off with the eight element open top. This so the antenna does not require anything done to stop the DC power going into the antenna.

    for a plain coco with no amplifier, then the 7.5 element with a shorted top is better.

    Comment


    • SIMULATION RESULTS FOR TWO VARIANTS OF 7.5 ELEMENT WHIPPED COCO

      SCREENSHOT 1 of 2 - Seven-and-Half (7.5) Element + 0.5 WHIP CoCo - OPEN TOP
      Gain = 7.78 dBi, SWR = 2.74 (mismatch loss = 1.06 dB)
      Net Gain Seen by Receiver = Antenna Gain - Mismatch Loss = 7.78 - 1.06 = 6.72 dBi

      coco 7.5 element + 0.5 whip open at top simulation output.png



      SCREENSHOT 2 of 2 - Seven-and-Half (7.5) Element + 0.5 WHIP CoCo - SHORTED TOP
      Gain = 9.67 dBi, SWR = 4.48 (mismatch loss = 2.24 dB)
      Net Gain Seen by Receiver = Antenna Gain - Mismatch Loss = 9.67 - 2.24 = 7.43 dBi


      coco 7.5 element + 0.5 whip shorted at top simulation output.png

      .
      Last edited by abcd567; 2014-04-16, 16:47.

      Comment


      • Originally posted by peterhr View Post
        Good work.

        ...so, if the user wants to use 'Satellite lead' amplifier that requires power up the cable (like one of these http://goo.gl/zDcQiW, with power inserter http://goo.gl/r1YRnx and suitable power supply ) then they might be better off with the eight element open top. This so the antenna does not require anything done to stop the DC power going into the antenna.

        for a plain coco with no amplifier, then the 7.5 element with a shorted top is better.
        The net gains (antenna gain - mismatch loss) of 7.5-element shorted & 8-element open are only marginally different.
        If you compare the radiation pattern of these, the 8-element open top pattern (minimum up/down lobes, maximum horizontal lobe) is much superior to 7.5-element shorted top pattern (lot of big up/down lobes).

        Comment


        • Originally posted by abcd567 View Post
          SIMULATION RESULTS FOR TWO VARIANTS OF 7.5 ELEMENT WHIPPED COCO

          SCREENSHOT 1 of 2 - Seven-and-Half (7.5) Element + 0.5 WHIP CoCo - OPEN TOP
          Gain = 7.78 dBi, SWR = 2.74 (mismatch loss = 1.06 dB)
          Net Gain Seen by Receiver = Antenna Gain - Mismatch Loss = 7.78 - 1.06 = 6.72 dBi

          [ATTACH=CONFIG]3900[/ATTACH]



          SCREENSHOT 2 of 2 - Seven-and-Half (7.5) Element + 0.5 WHIP CoCo - SHORTED TOP
          Gain = 9.67 dBi, SWR = 4.48 (mismatch loss = 2.24 dB)
          Net Gain Seen by Receiver = Antenna Gain - Mismatch Loss = 9.67 - 2.24 = 7.43 dBi


          [ATTACH=CONFIG]3901[/ATTACH]

          .
          That's good to know, I have a 7.5 + 0.5 Whip - shorted top and was hoping to improve but it doesn't look like that is going happen.
          I usually have around 230 NM but once I got 326 NM !! I That's only possible if the plane is at least 72,000 ft?
          Cheers
          Attached Files

          Comment


          • Originally posted by seahorse View Post
            ......I usually have around 230 NM but once I got 326 NM !! I That's only possible if the plane is at least 72,000 ft?
            Cheers
            The extra ordinary long range is due to data error. It happens with me ocassionally.

            Comment


            • Originally posted by abcd567 View Post
              The extra ordinary long range is due to data error. It happens with me ocassionally.
              or "ducting"

              Comment


              • Originally posted by Ressy View Post
                or "ducting"
                Yes, possible.

                Comment


                • I thought this was interesting ! A fellow Ham Op' from VE6 who winters in Israel..From my friend 4Z4TJ / VA6TJ who uses a Dongle to Rx ADS-B at his location.
                  squawk 7700 17 Apr 1506.jpg
                  Notice the 'squawk code' ? It does not look strange..until you read this article;

                  Emergency Transponder Squawk Codes

                  by Jason Schappert

                  One of the biggest falters in emergencies is the pilots failure to properly communicate the emergency. Knowing the emergency transponder squawk codes can help ATC evaluate your situation and notify help sooner or aid in getting you to the nearest airport.

                  Below are the 3 squawk codes every pilot should commit to memory:

                  7500 – Hijack
                  7600 – Lost Comm (radio failure)
                  7700 – Emergency

                  An easy way to remember this: 75 taken alive, 76 technical glitch, 77 going to heaven.

                  Interesting now, eh !
                  Jerry
                  F-CYQL1

                  Comment


                  • Originally posted by VE6CPP View Post
                    I thought this was interesting ! A fellow Ham Op' from VE6 who winters in Israel..From my friend 4Z4TJ / VA6TJ who uses a Dongle to Rx ADS-B at his location.
                    [ATTACH=CONFIG]3908[/ATTACH]
                    Notice the 'squawk code' ? It does not look strange..until you read this article;

                    Emergency Transponder Squawk Codes

                    by Jason Schappert

                    One of the biggest falters in emergencies is the pilots failure to properly communicate the emergency. Knowing the emergency transponder squawk codes can help ATC evaluate your situation and notify help sooner or aid in getting you to the nearest airport.

                    Below are the 3 squawk codes every pilot should commit to memory:

                    7500 Hijack
                    7600 Lost Comm (radio failure)
                    7700 Emergency

                    An easy way to remember this: 75 taken alive, 76 technical glitch, 77 going to heaven.

                    Interesting now, eh !
                    Jerry
                    F-CYQL1

                    Very Luckily, there is no 7400 - 74 in Cantonese is " go and die ". LOL
                    F-WSSS1 - Cats refused to Pee & Pooh on RadarBox - Running a FR24 Receiver & DVB-T Dongle 24/7 to piss off The Chief Thief.

                    Comment


                    • Originally posted by VE6CPP View Post
                      7700 – Emergency
                      I bet no one ever noticed the transponder in my Avatar was set to 7700
                      www.ADS-B.ca

                      Comment


                      • I've got these two 2.4GHz Omni WiFi antennas I want to rebuild or convert into 1090 MHz antennas. One of them is a 25 element and the other is a 29 element. Obviously those elements will all have to go and new elements will be cut and tuned. Basically I'm just taking advantage of the fiberglass housing, N connector, and mounting hardware.

                        http://ads-b.ca/wifi/

                        It should be interesting, as I will be working on this with a friend from Nav Canada that has all the test gear to simulate a 1090MHz signal so we can perfectly tune the new antenna design.

                        This is what he said:

                        You could easily fit 16 or more elements in there but the issue is that
                        we're using coax as a delay line, which makes it longer.

                        Anyway, each element whether it is the delay line or the radiating element,
                        will be 4.65 inches long assuming LMR4 velocity factor of 0.86.
                        A 4 foot radome will fit 10 elements, which in reality gives us 5 radiating
                        elements and 4 phasing lines, so really 9 elements.



                        Anyone have any more suggestions ?

                        Thanks!
                        www.ADS-B.ca

                        Comment


                        • Originally posted by 1090 MHz View Post
                          .........

                          This is what he said:

                          You could easily fit 16 or more elements in there but the issue is that
                          we're using coax as a delay line, which makes it longer.

                          Anyway, each element whether it is the delay line or the radiating element,
                          will be 4.65 inches long assuming LMR4 velocity factor of 0.86.
                          A 4 foot radome will fit 10 elements, which in reality gives us 5 radiating
                          elements and 4 phasing lines, so really 9 elements.



                          Anyone have any more suggestions ?

                          Thanks!
                          To my knowledge, each element of a Coaxial Collinear has BOTH the "Radiating" & "Phasing" lines. The inner wire acts as "Phasing line", while the outer shield/braid acts as "Radiating line". So we have two collinear Lines, each having multiple number of alternate "Radiating" & "Phasing" half wave sections.

                          The term "Radiating" is appropriate for Transmitting Antennas where RF power is radiated in space.
                          For Receiving antennas, more appropriate term is "Intercepting" as it intercepts the RF Power available in space.


                          .
                          Last edited by abcd567; 2014-04-20, 05:57.

                          Comment


                          • .
                            "RADIATING" and "PHASING" ELEMENTS IN COLLINEAR ANTENNAS
                            Please see two sketches below for Phasing/Radiating system for two types of collinear antennas:
                            Coaxial Collinear Radiating Phasing.jpg . Franklin Collinear Phasing Radiating.png

                            Comment


                            • .
                              The Collinear Principle

                              Since the antenna wire intercepts/radiates RF Energy, it is logical to think that "longer the antenna wire, more RF energy it will intercept/radiate". Unfortunately this benefit of long antenna is not achieved as the electromagnetic fields of adjacent 1/2 wavelength sections oppose and tend to cancel each other.

                              This problem is overcome by preventing alternate 1/2 wavelength sections from radiating/intercepting. This is commonly achieved in two ways:

                              (1) Shielding the alternate 1/2 wavelength sections by a metallic shield (like the inner conductor of a coaxial cable is shielded by it's braid), preventing the shielded 1/2 wavelength central wire from radiating/intercepting RF energy. This method is used in coaxial-collinear antenna.

                              (2) By collapsing alternate 1/2 wavelength sections upon themselves, making a fold. The electromagnetic field of one half of the fold is cancelled by the other half of the fold, preventing the folded 1/2 wavelength section from radiating/intercepting RF energy. This method is used in Franklin collinear antenna.

                              The non-radiating/non-intercepting sections pass the RF current from one radiating/intercepting section to other, and provide phase match between radiating/intercepting sections, and hence are "phasing" sections.
                              .
                              Last edited by abcd567; 2014-04-20, 16:59.

                              Comment


                              • .
                                DEVELOPMENT OF THE COCO

                                Please see sketch below:

                                Development of CoCo-rev1.jpg



                                .
                                Last edited by abcd567; 2014-04-21, 05:57.

                                Comment

                                Working...
                                X