Announcement

Collapse
No announcement yet.

best antenna

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

  • Originally posted by 1090 MHz View Post
    The attachments seem to be missing.... Invalid Attachment specified. If you followed a valid link, please notify the administrator

    [UPDATE] OK seems to be working now.
    Did you find these useful?
    Please also see the sketch which I have posted earlier: http://imageshack.com/a/img405/4527/evtm.png

    Comment


    • Originally posted by abcd567 View Post
      Did you find these useful?
      I certainly did! I was about to ask you how to connect the coax cable to the Franklin antenna but the pics are very clear and informative! Thank you!
      So far the best antenna I managed to build is a dipole made with the thin RG174 coaxial cable, which I have plenty of. The curious thing is that I did the two rods 136mm long with the very scientific reason of 'I can shorten them later'. This one can pick up signals 200km away from an indoor location near a big window, where the other dipole with the proper 68mm rods gets less planes at a shorter range. I'm sticking with the wrong one until a better effort.
      T-LIML5

      Comment


      • Here is another way to build the Franklin antenna http://www.lesaunier.com/htm/franklin1_eng.htm
        Liviu
        A.net JetPhotos.Net PlaneSpotters.net
        RTL USB/dump1090/FreeBSD + Franklin antenna + PlanePlotter

        Comment


        • Originally posted by Matic View Post
          I certainly did! I was about to ask you how to connect the coax cable to the Franklin antenna but the pics are very clear and informative! Thank you!
          So far the best antenna I managed to build is a dipole made with the thin RG174 coaxial cable, which I have plenty of. The curious thing is that I did the two rods 136mm long with the very scientific reason of 'I can shorten them later'. This one can pick up signals 200km away from an indoor location near a big window, where the other dipole with the proper 68mm rods gets less planes at a shorter range. I'm sticking with the wrong one until a better effort.
          It is odd that you got a better result with a full-wave dipole (2 x 13.6 cm). Half wave dipole has an impedance of about 75 ohms, which matches with impedance of coaxial & receiver. Full wave dipole has very high impedance, around 400 ohms which does not match with coaxial/receiver impedance, and have a high standing wave ratio.

          Please try other dimensions & configurations of dipoles, including the Franklin one I have shown, and compare results. It is quiet likely that you hit a very good design.

          Comment


          • Originally posted by nliviu View Post
            Here is another way to build the Franklin antenna http://www.lesaunier.com/htm/franklin1_eng.htm
            Thank you for sharing the link.

            Comment


            • Originally posted by abcd567 View Post
              It is odd that you got a better result with a full-wave dipole (2 x 13.6 cm). Half wave dipole has an impedance of about 75 ohms, which matches with impedance of coaxial & receiver. Full wave dipole has very high impedance, around 400 ohms which does not match with coaxial/receiver impedance, and have a high standing wave ratio.
              Does the fact that the RG174 is a 50 ohm cable have something to do about it?

              Originally posted by abcd567 View Post
              Please try other dimensions & configurations of dipoles, including the Franklin one I have shown, and compare results. It is quiet likely that you hit a very good design.
              I built a quick 4 elements Franklin antenna with 1.2mm diameter galvanized iron wire + 1m of RG174 and got slightly less range than the full-wave dipole. Since I haven't copper or brass wire I experiment with cheaper material. Also, I have no idea if the thickness of the wire makes a difference or not. Anyway today I got a five meters standard diameter coax cable with ferrites and connectors at both ends. I found later that it's 19VATC, which is just marginally better than RG174 in terms of attenuation. Good for keeping on with experiments.
              T-LIML5

              Comment


              • Originally posted by Matic View Post
                Does the fact that the RG174 is a 50 ohm cable have something to do about it?



                I built a quick 4 elements Franklin antenna with 1.2mm diameter galvanized iron wire + 1m of RG174 and got slightly less range than the full-wave dipole. Since I haven't copper or brass wire I experiment with cheaper material. Also, I have no idea if the thickness of the wire makes a difference or not. Anyway today I got a five meters standard diameter coax cable with ferrites and connectors at both ends. I found later that it's 19VATC, which is just marginally better than RG174 in terms of attenuation. Good for keeping on with experiments.
                I am now trying to find out why full wave dipole is not popular. May be it has problem of matching/radiation for TRANSMITTING, but good for receiving, though general principle is that if an antenna is good for transmitting, it is also good for receiving and vice versa.
                Best way is to keep trying different dimensions, formations, and materials and comparing results.

                Comment


                • Constructing any Multi-Elements antenna is easy.

                  What that is most difficult is to ensure the antenna is TUNED to 1060 MHz.
                  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 Birdie View Post
                    Constructing any Multi-Elements antenna is easy.

                    What that is most difficult is to ensure the antenna is TUNED to 1060 MHz.
                    For most of us the difficulty is finding what it is tuned to - I suppose that is where the difference is with a mass produced commercial antenna ... the design / prototype is tuned, then it's just a manufacturing job.

                    I think I'd prefer tuned to a little higher frequency though, but 1060Mhz - I'd be happy with ... it's only a little off - anything I make would be worse

                    Comment


                    • Originally posted by abcd567 View Post
                      I am now trying to find out why full wave dipole is not popular. May be it has problem of matching/radiation for TRANSMITTING, but good for receiving, though general principle is that if an antenna is good for transmitting, it is also good for receiving and vice versa.
                      Best way is to keep trying different dimensions, formations, and materials and comparing results.
                      Take a look at this site on antenna theory, it's very interesting: http://www.antenna-theory.com/antennas/dipole.php
                      www.ADS-B.ca

                      Comment


                      • Originally posted by 1090 MHz View Post
                        Take a look at this site on antenna theory, it's very interesting: http://www.antenna-theory.com/antennas/dipole.php
                        Originally posted by peterhr View Post
                        For most of us the difficulty is finding what it is tuned to - I suppose that is where the difference is with a mass produced commercial antenna ... the design / prototype is tuned, then it's just a manufacturing job.

                        I think I'd prefer tuned to a little higher frequency though, but 1060Mhz - I'd be happy with ... it's only a little off - anything I make would be worse
                        Originally posted by Birdie View Post
                        Constructing any Multi-Elements antenna is easy.

                        What that is most difficult is to ensure the antenna is TUNED to 1060 MHz.
                        Originally posted by Matic View Post
                        I certainly did! I was about to ask you how to connect the coax cable to the Franklin antenna but the pics are very clear and informative! Thank you!
                        So far the best antenna I managed to build is a dipole made with the thin RG174 coaxial cable, which I have plenty of. The curious thing is that I did the two rods 136mm long with the very scientific reason of 'I can shorten them later'. This one can pick up signals 200km away from an indoor location near a big window, where the other dipole with the proper 68mm rods gets less planes at a shorter range. I'm sticking with the wrong one until a better effort.
                        Most antenna books & sites discuss TRANSMITTING antennas.
                        What we need for ADS-B is a RECEIVING antenna.

                        TRANSMITTING Antenna:
                        For Transmitting antenna, the most important criteria is that the antenna should be capable to radiate in space ALL the power which the transmitter can deliver. For efficient transfer of energy, the impedance of the transmitter, the antenna and the transmission line (coaxial cable) connecting the transmitter to the antenna must be the same. The antenna is called "RESONANT" or "TUNED" if this is achieved. Transmitters typically are designed for 50 Ohms impedance, and the coaxial cables (transmission lines) used with them also have 50 Ohms impedance. Some antenna configurations often have an impedance other than 50 Ohms and impedance matching circuit is then required to transform the antenna impedance to 50 Ohms.

                        For Transmitting antennas, another way to measure the extent of power transfer is Standing Wave Ratio (SWR or VSWR). A VSWR of 2.0:1 or less is often considered acceptable. Most commercial antennas are specified to be 1.5:1 or less. Based on a 100 watt radio, a 1.5:1 VSWR equates to a forward power of 96 watts and a reflected power of 4 watts, or the reflected power is 4.2% of the forward power.

                        RECEIVING ANTENNA:
                        The RECEIVING antenna is not intended to radiate power. Its function is to intercept the electromagnetic waves transmitted by transmitters, and feed this intercepted power into coaxial cable & receiver. The most important criteria for RECEIVING antenna is therefore to intercept maximum amount of electromagnetic radiation, and then to transfer it to the receiver. Larger the physical size (length) of antenna, larger amount of Electromagnetic radiation it will intercept and produce larger amount of power to feed to the receiver. Impedance matching results in maximum transfer of power from antenna to receiver, but this can be achieved by matching circuits or matching transformers (balun). There is no need to limit the size of receiving antenna to 1/2 wavelength just to achieve "RESONANCE", and thus limit the intercepted power.

                        A short 1/2 wavelength Dipole (or 1/4 wavelength Monopole with ground plane) is a reasonably good solution for TRANSMITTING antenna, but is not so good for receiving antenna due to its short length limits the interception of amount of available electromagnetic radiation. A larger antenna with impedance matching circuit/balun give better received signal strength.
                        Last edited by abcd567; 2013-10-03, 15:46. Reason: Quotations added from other posts with same answer.

                        Comment


                        • Originally posted by 1090 MHz View Post
                          Take a look at this site on antenna theory, it's very interesting: http://www.antenna-theory.com/antennas/dipole.php
                          Very informative indeed. Thank you for sharing.

                          Comment


                          • What’s the best antenna?
                            If there was just one “best” antenna, everybody would use it. The best antenna for one particular situation may not work well somewhere else. There are three rules of antenna installation:
                            • Any antenna is better than no antenna.
                            • Bigger and higher are generally better. If small antennas really did work as well as big antennas, nobody would spend the time, money and effort to put up the big ones.
                            • Every antenna installation is a compromise.

                            There are several factors that must be considered when engineering an antenna installation. Height? Size? Weight? Restrictions? Cost?

                            Now there is a factor that we all have to compromise on with every antenna, cost. Should I build it or buy it? Many antennas can be scratch built for a fraction of what they cost readymade, but are they bargains? Mostly antennas are advertised for $75 to $150 but the same performance can be had from a home built antenna costing less than twenty dollars. A vertical antenna can be constructed from electrical conduit or Aluminium or copper tube for a few bucks, however they may be difficult to design and tune if the Amateur doesn’t have a background in engineering or key pieces of test equipment. The truth is, when you buy a ready-made antenna, you aren’t just buying a collection of aluminum tubing, you are also purchasing design expertise.

                            Do you get your money’s worth? Is the kit of parts complete? Is the hardware stainless steel, or are you going to have to deal with a corroded mess after a couple of years? Are the directions clear, and detailed? Some antenna manufacturers provide a single sheet with a quick sketch whereas others provide a manual running to several pages. Usually the bulk of even a complex antenna is fairly straightforward in assembly, with a single part requiring tuning. When you get to the tuning, either (1) the manufacturer has designed the assembly so it could be tuned at the factory; or (2) he has provided detailed instructions on how to accomplish the procedure; or (3) the instructions are vague and misleading; or (4) you are left on your own. The author has experienced all of these conditions.

                            The quality of the instruction manual is of primary importance when selecting a ready-made antenna. Some engineer built a number of prototypes to come up with the design the manufacturer decided to market. Assuming they started with exact copies of the pieces of that antenna, the manual should lead you by the hand to assemble those pieces into a good enough copy of the original to equal the performance advertised. A low cost antenna is no bargain if you cannot properly set it up for peak performance.

                            What should be height of ADS-B receiving antenna? The range is basically determined by height of the aeroplanes which are several thousand feet high. However the receiving antenna should be high enough for low flying aeroplanes, and to overcome obstructions of terrain (such as tall trees, buildings, hillocks etc). In many cases, a tower isn’t necessary. When you think “tower”, remember that your house roof may already be a good height already.

                            One way to answer the antenna question would be to ask, “What does a ‘typical’ ADS-B amateur use?” There is no ‘typical’ ADS-B station; any more than there is a ‘typical’ amateur. However, given the same engineering problem, the solutions tend toward a common theme. Some ADS-B amateurs, who routinely receive ADS-B, have a tower. The most common height is in the 60-70-foot range. On the top of the tower is mounted a 0.5 to 1.5 meter antenna. There is then a coaxial cable running into the receiver. Is this the “best” antenna? Not necessarily. Many amateurs have to compromise this arrangement due to zoning laws, and deed covenants. This arrangement may not be possible in all locations. The best antenna for you will be as personal as the best pair of shoes would be. Simple, easy antennas are a smart start. You can start with a dipole (1/2 wave or full wave or 4 or 6 element franklin collinear). More elaborate (and expensive) antennas should be carefully researched. The experienced Amateur should be able to decide what limitations his or her own situation imposes on the potential choices.

                            Objects and landforms in the environment profoundly affect radio waves arriving at an antenna. Will the antenna be ground mounted or elevated? Close to a building or in the clear? Mounted on a tower, pole, building? How much will the whole installation cost? Will the neighbors (or spouse) object?

                            The antenna system is the single most important component of an ADS-B receiving station. It defines the performance of the entire station. Consider the choices carefully, because only you can really answer the question:
                            What is the best antenna?


                            ***Adapted and modified for ADS-B by abcd567, from an article written by Amateur Radio Operator NM7R for ham radio amateurs.


                            .
                            Last edited by abcd567; 2013-10-07, 23:02.

                            Comment


                            • I've been trying to source a company that makes the real ADS-B antennas used in actual ATC installations. It seems there are a few different companies out there making and developing the ADS-B systems, and they also make their own antennas for the purpose. In the following photos you'll see some actual installations and the antennas used. Most seem to be just a simple omnidirectional with a full wave length of 1090 MHz = 27.5 cm.
                              Attached Files
                              www.ADS-B.ca

                              Comment


                              • Pleanty of short stumpy ones around here like that too. But also some longer tapered whips
                                Posts not to be taken as official support representation - Just a helpful uploader who tinkers

                                Comment

                                Working...
                                X