Announcement

Collapse
No announcement yet.

best antenna

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

  • @ccz:
    I did not understand your photo below. What is this? If you passed the core wire of feed coax all the way through the F female barrel to make the whip, then this is a very smart idea. I will also try this.

    Last edited by abcd567; 2016-08-17, 18:55.

    Comment


    • Originally posted by abcd567 View Post
      @ccz
      At last, after long wait...
      Nice to read detailed report. At microwave, the hardware often behave unexpectedly. The net result is combination of many factors, and combination of little difference in each can result in substatial difference in overall performance.
      Amazingly unexpected and the slightest misalignment/length mistakes produces a unworkable fixture.


      Originally posted by abcd567 View Post
      Glad to see you broke the tradition of using SO239 connector (good only for VHF) and N connector (for UHF) and used F connector which is designed for microwave frequencies. The idea of soldering the radials to the nut is good. Others who used F connector, have soldered radials on the washer.
      To be sincere, I was put off by the price of those connectors and the fact that F ones are readily available in almost any stores. Plus that they are used for SAT frequencies was reassuring enough.
      The only specialty connectors I've bought are the MCX ones. I'm trying to avoid adapters or any other connectors on the cable run. As short as needed and as directly connected as possible seems to give the best results here.

      I did try at first soldering to the washer but it was not sturdy enough for me. The nut, if soldered properly gives a much tougher result.


      Originally posted by abcd567 View Post
      Since in the new spider you have placed few turns of wire below the nut, raising radials to the level where the whip starts, this might have improved the performance of your new spider.
      This and using a continous center wire from cable trough F connector then the F joiner and to the whip also helped a lot too.


      Originally posted by abcd567 View Post
      For outdoor use put few drops of hot melt glue or a sealent to prevent rain water or moisture entering the coax and corroding its braid and center conductor.
      I will mix some fluid bicomponent gle and pour it around. That should take care of any moisture even better than silicone.

      Originally posted by abcd567 View Post
      @ccz:
      I did not understand your photo below. What is this? If you passed the core wire of feed coax all the way through the F female barrel to make the whip, then this is a very smart idea. I will also try this.

      Exactly what I did, that picture is just to show an example that it is possible. At least with part of the F female barrels that I got.
      I hated the fact that the whip was always moving around and the connection is actually pretty flimsy since there is no cable and F connector to support it. Plus the fact that from whip to MCX connector there's nothing else besides the small cable run.

      I will have to post a picture of how I soldered the MCX connector to the RG59 cable.

      PS: the wire through the barrel was at one time a radial for a spider connected just by tightening the nut. They were each (3 doubles making 6 total radials) at different height on the F connector. Not the best option but it worked nicely for a few tests.
      Last edited by ccz; 2016-08-18, 00:20.

      Comment


      • @ccz
        Great! Very innovative!
        Thanks for detailed explanation.

        Did you see my following two posts?

        (1) Radials tightened by the nut. Click here (post #5) .


        (2) The coax core continues to make an integeral whip. Click here.

        .

        Comment


        • I've seen them both a long time ago.
          I think that the inspiration for the integral whip came from your no.2 post.


          I had holidays but managed to finish 2 new antennas before leaving and tested them today.

          They are pretty directional after 80-90nm but before that distance I seem to receive a lot of planes too. Maybe a lot of them are due to reflections.
          The beam seems to be about 90 degrees wide. It catches double the amount of planes in that direction (compared to a 1/4 whip).
          The message rate at ranges over 80nm is greatly improved indicating that it really has more gain.

          It would be nice if it would be possible to stack 4-6 of these and feed them into 1 receiver but sadly it isn't possible from what I have read.


          Construction:

          Simple one:
          1 x sheet 25/25cm of aluminum
          1 x F connector
          copper wire (from RG cable or other sources)

          Double version:
          1 x sheet of 50/25cm of aluminum
          1 x F connector
          copper wire

          For both versions the sides of the sqares are 68.8mm.
          The antenna is mounted 34.4mm away from the reflector.
          I read that most people are shielding the main 2 posts that connect the antenna to F connector/joiner.
          I have used the shielding from the RG cable for that.



          20160824_191708.jpg20160824_191647.jpg20160824_191723.jpg20160824_191737.jpg20160824_191732.jpg

          Comment


          • @ccz
            Wow great!
            Bi-quad & double bi-quad. I never tried this, but you inspire me to make one. Will do it on some week-end.

            Mixing RF signals of 4 antennas and feeding to 1 receiver is tricky, and requires accurate phasing harness.

            Mixing in software (VRS, modeSMixer etc) 4 bi-quad is possible if each antenna is connected to its own dedicated receiver. For 4 antennas, 4 receivers (dvb-t) are required. This is a costly solution, but possible.

            Yes, I did use idea of integral whip, but it did not allow use of a connector. Your idea to pass the integral whip all the way through the F female barrel connector is brilliant.
            Last edited by abcd567; 2016-08-24, 21:13.

            Comment


            • Double bi-quad works visibly better for longer range.
              For medium range I can't say anything yet, I have to do at least some 24h tests on same weekdays.

              Bi-quads are excellent for window antennas. I am picking up reflections up to 120nm on the opposite side of the antenna.

              Calculator link:
              http://buildyourownantenna.blogspot....alculator.html

              Tips:
              The reflector plate should not be smaller than recommended size.
              Thicker wire seems to work better than thinner wire. For 1090MHz 2.6mm diameter is recommended - I used 1.78mm dia (2.5 sq.mm)


              To do:
              - try a better wire thickness: 2.6mm diameter (5.30sq.mm)
              - try a mesh for reflector - thin mesh - simply because it is available at a nearby store
              - try a rounded double bi-quad - regular double bi-quad turned around a can as reflector

              @abcd
              If you have the spare time and if it is also possible to simulate the rounded double bi-quad, that would be interesting.


              Edit:
              found the omnidirectional biquad here: https://www.youtube.com/watch?v=4t6OliwhJ5g
              going to test it tonight!

              Comment


              • Ive made "bow tie" antennae myself - for wifi, with good success.... but a thought just occurred, looking at your build...

                What if you made several quads, and mounted them to the outside of a cylinder ? Theoretically that would give omnidirectional coverage !

                Comment


                • Test base antenna (1090 Mhz) from Bulgaria vs. PCB antenna vs. CoCo antenna all without filter and without LNA:
                  Total height position antenna (roof top) is 6 meters.
                  Maximum range Base Antenna (1090 Mhz) from Bulgaria: poor receiving < 50nm
                  Base Antenna (1090 Mhz) from Bulgaria.JPG

                  Maximum range PCB antenna: 105nm The cable i’m used is the 50 Ohm H155
                  PCB antenna.jpgPCB on top.jpg

                  Maximum range CoCo antenna: 202nm The cable i’m used is the 75 Ohm 707CRT2
                  coco.jpgSuper coco.jpg

                  I am now a week on holiday, later continued by testing the same antennas with "Flightaware 1090 MHz filter and a cheap satellite antenna amplifier (LNA)

                  Comment


                  • @Ronny Jonckers
                    Glad to hear that your DIY CoCo gave the best performance. Happy experimenting!

                    Comment


                    • Originally posted by Rooster View Post
                      Ive made "bow tie" antennae myself - for wifi, with good success.... but a thought just occurred, looking at your build...

                      What if you made several quads, and mounted them to the outside of a cylinder ? Theoretically that would give omnidirectional coverage !

                      In theory and only at first glance.
                      I have tried rounding a little bit a double biquad that I made. The ground plane (and biquads) was rounded to cover 180 degrees so that it looked like half a circle.
                      Not the slightest improvement. Reception was a lot worse.

                      I have also tried quads intersecting each other at the whip, 4 quads looking from above like an X. Reception was worse compared to a spider.


                      @Ronny Jonckers

                      Please try building a spider or cantenna. These are very good base references to test your other builds against.
                      75ohm cable works best (for me).



                      Regarding omnidirectional quads, i am proposing this design, that I also hope to test soon:
                      Attached Files

                      Comment


                      • I am experimenting now with a stub filter since I don't want to shell more money at the moment to buy a special filter.

                        I have no DC blocker so the stub filter sits between DC injector and RTL stick. Optimally, this should be in front of the amplifier but since there is a short on the stub and I don't have any DC blockers, I can't use it that way.
                        20160915_150633.jpg
                        This is a pass filter for 1090MHz so the end of the stub is shorted (soldered). If one would like to block 1090MHz for example, the stub would be open ended.

                        In theory the length of the stub should be quarter wavelength * cable velocity factor. Because this is RF, the optimal length needs to be found. Cut a longer stub, 20mm longer should be enough, and check the signal over a period of time to find YOUR optimal length.

                        Until now I have tried 4 possibilities:

                        stub (mm) w/o amp w/ amp
                        no stub 4500 fpm 3200 fpm
                        78.08 4500 6300
                        68.8 6300 5000
                        57.7 4700 3400
                        Frames per minute where taken from adsbSCOPE 2.7. If anyone has a better idea for signal quality/quantity checking, please let me know, I'm very interested. Just to clarify, data must be fetched from a RPi on local network.
                        Last edited by ccz; 2016-09-15, 12:22.

                        Comment


                        • @ccz:

                          I use Performance graphs (message rate: 1 hr or 6hrs) for performance checking.

                          The best way to install these graphs is to use a spare microSD card and burn the OS image (like Raspbian Jessie Lt), then install the dump1090-mutability, data feeders & Performance graphs. This way you dont disturb you existing installation. If you dont like the new one, simply remove new microSD card and insert the old one.

                          I first formatted microSD card, burned Jessie Lt img from raspberrypi.org, then installed rest of things using automated script as follows:
                          Code:
                          sudo apt-get update
                          sudo apt-get install git
                          git clone https://github.com/jprochazka/adsb-receiver.git
                          cd ~/adsb-receiver
                          chmod +x install.sh
                          ./install.sh
                          The above automated script first installs dump1090-mutability.
                          After this it gives options to install
                          1. dump978 - only useful for USA. I did not install it.
                          2. Data feeders (Flightaware, Planefinder, Flightradar24, adsbexchange). You can choose whatever you like to install.
                          3. Web Portal which includes rrdtools/collectd, and database XML/MySQL Lite/MySQL. DO NOT choose ADVANCE option. It will install MySQL and unnecessarily keep on writing airplane data to your microSD card, and shorten its life.

                          For details, see this page:
                          https://github.com/jprochazka/adsb-receiver

                          .

                          Comment


                          • This is how I use Performance Graphs to compare antennas

                            A Simple Experiment to Demonstrate How Ground Plane Radials Affect the Performance of An Antenna

                            A 1/4 Wavelength Monopole Whip was tested under following conditions:
                            (1) Only Whip, no ground plane radials.
                            (2) Whip with horizontal ground plane radials.
                            (3) Whip with 45 degrees slanting ground plane radials.

                            The attached performance graphs show the importance & affect of ground plane radials.

                            Image 1 of 5
                            Device Under Test: 1/4 Wavelength Monopole, without & with radials







                            Image 2 of 5
                            Three Test Setups





                            Images 3, 4, & 5 of 5
                            Performance Graphs





                            Comment


                            • Great, thanks abcd567!
                              Finished installing it on my second receiver, works like a charm.
                              Installing it now also on my main receiver.

                              Comment


                              • are you zip tying the radials to outside of cable, or stuffing them down in the insulation. My eyes are not what they used to be?

                                Comment

                                Working...
                                X