Announcement

Collapse
No announcement yet.

3 EASY ANTENNAS FOR BEGINNERS

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

  • ...are we still under the topic easy antennas for beginners?

    Comment


    • Originally posted by Sam26K View Post
      They key to minimal loss between antenna and receiver is to put the USB stick as close to the antenna as possible.. USB sticks are cheap, good quality low loss coax is not so cheap. If you use a good quality USB cable you can easily have a run of 15' feet from the USB stick to the pi or computer without a problem with 5VDC source loss.

      Otherwise if you have a long run of coax from the antenna to the receiver, an inline amplifier is the solution. A power supply is required. Did anyone come up with a good solution for the inline power amp? TIA!
      Full ack!

      If you want to build a cantenna, the easiest and far best way is to use only the F-pigtail and directly house the receiver stick inside the can.
      You may use a 10m usb repeater cable that will not cost much more than the 10m F-cable that you won't need anyway.
      Forget amplifiers, avoiding losses in HF lines is much more efficient!
      Every additional HF connection weakens your signal, the receiver has enough gain anyway!

      By the way: you should use a 10cm stable food can. It can be fixed using cheap sewing pipe clamps.
      You should also cover can and antenna with a matching plastic funnel, else water will accumulate onto the can. :-(
      Last edited by RIN67630; 2016-03-23, 08:06.

      Comment


      • Originally posted by RIN67630 View Post
        Here ist the detail view of the balun und the coax connection:
        http://www.cjoint.com/doc/16_03/FCwi...322-090136.jpg
        The dimensions are given here:
        http://www.hamuniverse.com/jpole.html
        Looking at the dimension calculation for the J-Pole and your picture: the feed point and spacing shall be 0.006 m = 6 mm. Did I misunder this or is your spacing bigger and the feed point in a different distance? As I read in another post it makes a huge difference if the feed point is just a little bit off the correct postion? Just asking because I might give it a try...
        JRF: T-EDNY19
        South Germany

        Comment


        • I have been using ~1,7mm wire. The distance is to be measured from the metal surface to metal surface, not from center to center.
          Additionally the formula ist valid for a rectangular J shape. The bend radius of the wire being quasi circular, the distances should approximately match.
          Of course it could be optimized, but then you need a HF-sender and a SWR meter.
          Last edited by RIN67630; 2016-03-23, 10:48.

          Comment


          • Originally posted by jrf View Post
            Looking at the dimension calculation for the J-Pole and your picture: the feed point and spacing shall be 0.006 m = 6 mm. Did I misunder this or is your spacing bigger and the feed point in a different distance? As I read in another post it makes a huge difference if the feed point is just a little bit off the correct postion? Just asking because I might give it a try...
            Originally posted by RIN67630 View Post
            I have been using ~1,7mm wire. The distance is to be measured from the metal surface to metal surface, not from center to center.
            Additionally the formula ist valid for a rectangular J shape. The bend radius of the wire being quasi circular, the distances should approximately match.
            Of course it could be optimized, but then you need a HF-sender and a SWR meter.
            I have not yet built any J-Pole, but during 2013/2014 did experiment with Franklin dipole having an impedance matching stub.
            Please see my 2013 post here: http: //forum.flightradar24.com/threads/3831-best-antenna?p=43396&viewfull=1#post43396

            1) It was made of core wire of RG6 coax, which has 1 mm dia (18 AWG).
            2) The stubs were U shaped and not rectangular. I found the optimum location of coax tap-off point at 18 mm from tip of U.
            3) Tried two matching stubs with different gaps between parallel wires of the stub, one with 10mm and other with 5mm gap. Found 5mm gap gave better results.


            .

            Comment


            • Has anyone got the dimensions of the Flightaware 1090MHz filter?
              Could it be, that its metal can has intrinsically the correct dimension to work as a cantenna?
              so the easiest way would have been just to stick a 68mm long piece of wire in its input and to wind 4 loops of cable at the other side to build a balun?

              Comment


              • Originally posted by abcd567 View Post
                The trickiest thing in J-pole, Slim Jim and Franklin dipole with matching stub is the accurate placement of cable tap off on the stub. At Ghz frequencies, few mm away from optimum point, and the antenna transforms from "very good" to "poor".
                I made another antenna deliberately placing the tap point 12 mm from the bottom:
                DUMP1090-Antenna2.jpg

                That one worked also pretty well, maybe the right point is around 9mm?
                Anyhow these antennas are really easy to build and perform much better than the shortened stock whip.

                Comment


                • Originally posted by RIN67630 View Post
                  Has anyone got the dimensions of the Flightaware 1090MHz filter?
                  Could it be, that its metal can has intrinsically the correct dimension to work as a cantenna?
                  so the easiest way would have been just to stick a 68mm long piece of wire in its input and to wind 4 loops of cable at the other side to build a balun?
                  This is not going to work. The basic requirement of a coaxial antenna (and it's wide-bodied varient Cantenna), is that the sleeve is connected to ground at top, but isolated from ground at bottom. The cylinderical metallic housing of Flightaware Filter is connected to ground both at top & bottom. Please see the drawing below.

                  Please note that the coaxial antenna at right, although an old design, was not very popular as it did not have as good performance as other dipole designs. I realized that the narrow dia of copper pipe/tube has resulted in very narrow air gap between coax and tube, and this was the main reason of its poor performance. I then decided to use a much larger dia sleeve to enlarge the air gap, and this proved successful, and was birth of the Cantenna. I did try narrow dia sleeve made of 3/4 inch (20 mm) dia copper pipe, another with medium dia (54mm) drink can, and third with wide dia (68mm) Pepsi can. The 68mm dia can proved best, and 20mm dia pipe proved worst.

                  (English translation in red added by me)

                  Last edited by abcd567; 2016-03-29, 23:25.

                  Comment


                  • @RIN67630:

                    https://en.m.wikipedia.org/wiki/J-pole_antenna

                    http://www.hamradio.me/antennas/impr...e-super-j.html


                    Last edited by abcd567; 2016-03-31, 20:25.

                    Comment


                    • careful this is turning into a not so easy antenna thread.
                      T-EGLF8

                      Comment


                      • Originally posted by SpaxmoidJAm View Post
                        careful this is turning into a not so easy antenna thread.
                        My words. The Jpole is the easiest. It fits in a piece of 16mm PVC tube.
                        Forget amplifiers, forget expensive coax cables and connectors, adapters etc...

                        The trick is to use the short stock cable and place receiver and Pi close to the antenna.

                        I get ~280nM every day and my current antenna location is far from being perfect, it is still not above the roofes around.

                        T-EDLW40 Statistics (from an average day):
                        STATUS: Online CURRENT UPLOAD RATE: 0 KB/S FIRST SEEN ONLINE: 2016-01-03 22:59:14
                        LOCAL IP: N/A MAC ADDRESS: 00:00:00:00:00 COORDINATES: 51.3684,7.9404
                        UPTIME (AS % OF AVAILABLE TIME): 100% AIRCRAFT SEEN: 1,788 POSITIONS REPORTED: 84,496
                        MAXIMUM DISTANCE: 286nm
                        Last edited by RIN67630; 2016-04-02, 03:01.

                        Comment


                        • @RIN67630:
                          Your statistics with J Pole antenna are great, congratulations!
                          What were your statistics with 1/4 λ groundplane antenna?

                          A comparison of two statistic will quantitatively highlight the difference of J Pole and 1/4 λ groundplane antennas.

                          Comment


                          • Hi there!
                            Is power inserter the same as power/voltage separator as I can't find "power inserter" analogue here in Poland.
                            9e7061014cd8b3e0c0b0bb1ccfd1.jpeg
                            ww.JPEG
                            or something like this:
                            ww2.JPEG

                            thanks for help!
                            T-EPLL59

                            Comment


                            • Originally posted by Faddah View Post
                              Hi there!
                              Is power inserter the same as power/voltage separator as I can't find "power inserter" analogue here in Poland.
                              Yes, it is same.
                              This one (ASZ-03R) is OK if you want to use one receiver (DVB-T) with one antenna
                              9e7061014cd8b3e0c0b0bb1ccfd1.jpeg
                              ww.JPEG

                              This one (ASZ-04/2) is OK if you want to use two receivers (DVB-T) with one antenna. If you connect two receivers (DVB-T), the signal will be divided between the two, and each will get half the strength.
                              ww2.JPEG

                              Comment


                              • Can anyone explain - in simple terms - the differences between having 3 -4 - 6 or 8 radials. I've seen examples of all these and would assume 8 is best but does this affect the operation ?

                                ylis

                                Comment

                                Working...
                                X