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  • Originally posted by mem0tap View Post
    Despite designing my own antennas I'm not an antenna expert, nobody is, it's a black art, guided by experience and a few rule of thumb calculations. I reckon for every successful antenna there's a few dozen in the bin!
    Fully agree

    Comment


    • Below are the simulation results for a CoCo (8-Elements, made of coax VF=0.86).
      These results show how a 1 or 2 mm error in element length can grossly affect SWR and Radiation pattern.
      Gain is relatively less affected by 1 or 2 mm error.

      The error in element length can either due to using wrong VF, or wrong cutting or a combination of both.

      In this simulation the a VF of 0.86 was used, giving element length 118 mm.


      SWR vs Element Length




      Gain vs Element Length




      Radiation Pattern vs Element Length




      Comment


      • Originally posted by abcd567 View Post
        Rooster:
        [ATTACH=CONFIG]9675[/ATTACH] [ATTACH=CONFIG]9675[/ATTACH] [ATTACH=CONFIG]9675[/ATTACH]
        Fully agree with you.

        Glad to see you after a long gap. Welcome back.
        Thanks mate - keep lurking, but not a lot has happened on here :-(

        Comment


        • Screenshot from 2018-07-20 23-06-53.png - results of my 'new' waterpipe antenna. fitted around midday Tuesday, it's mounted 7 feet below Jetvision antenna (which yields around 2400 a day, Since it looks promising I've upped the anti a touch and building an 8 section 22mm outer, 8.5mm inner air spaced.

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          • Got up on the roof today and relocated the FR24 antenna from its previous location on the side fence to above the TV antenna... now sitting about 1.2m above the highest point of the roof-line...
            (also solved a TV reception issue)
            FR24 antenna on roof.jpg

            (shot of previous location in this post https://forum.flightradar24.com/thre...l=1#post105113)
            Last edited by petercr; 2018-08-04, 07:15.

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            • Horseshoe Antenna

              Found a very interesting horseshoe antenna made by galenthurber.
              Please see this thread

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              • SIMULATION OF HORSESHOE ANTENNA


                Gain = 3.2
                SWR = 3.5






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                • IMPEDANCE MATCHING STUB ADDED TO HORSESHOE ANTENNA

                  Untested proposal. Expected to bring down SWR from 3.5 down to < 1.5

                  Comment


                  • Delved into this thread a few weeks ago, and started out with a cantenna for my first DIY antenna build. Surprisingly good results! Got about 160nm range from my south-facing apartment window.

                    So, naturally I want to see how far I can take this project, so I tracked down some SO-239 connectors, and this past week I soldered together a 4-legged spider antenna (see attached photo - no idea how to rotate it, sorry!). Measured roughly, bent the wires haphazardly, and mounted it in PVC piping with tape on the brick outside the window. Seeing about a 10% increase in data from this antenna over the cantenna. Pretty cool! I have a few questions for anyone who cares to chime in:


                    1. For someone who's new to antenna design and theory, how important is it that I seal/weatherproof the connection between the center wire and the SO-239 core element? I've seen mention of sealing, weatherproofing, and enclosing these antennas, but how important is it really?

                    2. Would a more accurate measurement and completely straight wires help the antenna perform much better, or is that a nominal difference?

                    3. Would soldering more wires on (say, 4 more to make it an 8-legged spider) make a big enough difference?

                    4. Compared to those options above (improvements), would the better choice be to add an in-line amp?

                    My apartment is up pretty high, but the antenna can only see South, East, and West. Almost zero north coverage due to the building and the mountains directly to my north.

                    Thanks for the help!
                    Attached Files

                    Comment


                    • Originally posted by aesoprrp View Post
                      1. For someone who's new to antenna design and theory, how important is it that I seal/weatherproof the connection between the center wire and the SO-239 core element? I've seen mention of sealing, weatherproofing, and enclosing these antennas, but how important is it really?
                      It is not very essential. Lot of people use it without any sealing, weatherproofing, and enclosing.

                      It works ok without sealing / water proofing. However after some period (say 1 to 3 years, depending on local weather conditions), rust & moisture set-in, and performance drops, or fails altogether.

                      Applying water sealing increases the span of trouble free service.

                      Originally posted by aesoprrp View Post
                      2. Would a more accurate measurement and completely straight wires help the antenna perform much better, or is that a nominal difference?
                      Depends how inaccurate it is initially. These antennas are very tolerant to dimensional errors, and will work OK even when built with an average skill. Making wire length, straightness of wires, and angle of bend more accurate may give an improvement of say 5% ~ 10% if it was originally build with an average skill.


                      Originally posted by aesoprrp View Post
                      3. Would soldering more wires on (say, 4 more to make it an 8-legged spider) make a big enough difference?
                      It does make an appreciable difference, say 10% to 20%, but not a BIG difference.

                      Originally posted by aesoprrp View Post
                      4. Compared to those options above (improvements), would the better choice be to add an in-line amp?
                      First you should try improving the antenna.
                      After antenna improvement is done, then add an amplifier.
                      Last edited by abcd567; 2019-01-19, 18:30.

                      Comment


                      • Originally posted by abcd567 View Post
                        First you should try improving the antenna.
                        After antenna improvement is done, then add an amplifier.
                        Good advice, thanks! Just straightened out my radials, added 4 more to make it an 8-legged spider, and I'm already seeing an improvement. I'll post back with results after a few days.

                        Comment


                        • Weather proofing makes ALL the difference, moisture is drawn into the coaxial cable like a sponge... even a night out with dew will draw in water - doesnt need to rain !!!
                          Ive seen many a cable ruined this way, and theres no recovery... ALWAYS seal the end of the cable - beeswax, self amalgamating tape etc.
                          Once moisture enters the cable the losses mount up exponentially...

                          Comment


                          • How-to Protect Outdoor Connectors and Cable From Ingress of Moisture (Due to Rain & Snow) and Resulting Short circuit, Corrosion, and Drop in Performance.

                            The simplest way to protect your connectors and cable from ingress of moisture is to wrap self-amalgamating / self-fusing / self-bonding tape over the connectors. Please do NOT use ordinary electrical PVC tape as it wont protect properly, and soon deteriorate.

                            An additional step in case of RG6 cable is to use Water Resistant type F-connectors which have built-in O-rings.

                            Examples of applying self-fusing tape on antenna and coax connectors are given below:




                            .
                            .




                            .

                            .

                            https://www.amazon.co.uk/gp/aw/s/ref...lgamating+tape
                            .



                            .

                            .

                            Last edited by abcd567; 2019-01-22, 04:13.

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                            • This is the one I use, Silicone Self-sealing Tape: https://www.homedepot.ca/en/home/p.t...00104039.html#
                              It's in the electrical section.
                              www.ADS-B.ca

                              Comment


                              • Originally posted by 1090 MHz View Post
                                This is the one I use, Silicone Self-sealing Tape: https://www.homedepot.ca/en/home/p.t...00104039.html#
                                It's in the electrical section.
                                Thanks!

                                Also, I’m looking for input on mounting solutions. Basically I need to figure out how to securely attach my antenna mast to the side of my building without drilling any holes (renting an apartment).

                                The outside of my building is brick, and the brick protrudes about 1/4” from the mortar. I found some “brick clips” (like this: 4 Metal Brick Clip Fastener Hooks ) meant for hanging pictures, so my first idea is to somehow attach a PVC pipe to the brick clip, and then attach the mast to the PVC with either an elbow joint or something similar. The idea here is to get the antenna out away from the side of the building, ideally about 8” or so. However, I’m not sure that the brick clips are sturdy enough to support the weight of the mast + antenna.

                                Option 2 would be to attach the mast to the fire escape railing outside one of my windows. The fire escape is of a fairly rudimentary style - just a ladder surrounded by a cage, not one of the (safer) stairway varieties. This option would be my first choice, but the closest window to the fire escape is also farthest from any interior power supply, so I’d have to run the coax cable quite a distance along the outside of the building to feed it through a different window where I can easily attach it to my RPi.

                                So: has anyone successfully made an antenna mast that can:

                                • attach to a window without drilling holes?
                                • Attach to a brick facade without drilling holes?
                                • Cleverly use gravity to “pin” the mast against the building?

                                I've looked into using some kind of flag pole mounting solution, but so far it looks like I’ll have to Macgyver my way to a stable solution.

                                Thanks for any help!

                                Comment

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