Page 258 of 284 FirstFirst ... 158208248256257258259260268 ... LastLast
Results 2,571 to 2,580 of 2840

Thread: best antenna

  1. #2571
    Passenger
    Join Date
    Jul 2016
    Posts
    19
    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!

  2. #2572
    Purser Rooster's Avatar
    Join Date
    Nov 2013
    Posts
    158
    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 !

  3. #2573
    Passenger Ronny Jonckers's Avatar
    Join Date
    Aug 2016
    Location
    T-EBZR7 Zoersel (Belgium)
    Posts
    9
    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)

  4. #2574
    Captain abcd567's Avatar
    Join Date
    Sep 2013
    Location
    Toronto CYYZ
    Posts
    2,835
    @Ronny Jonckers
    Glad to hear that your DIY CoCo gave the best performance. Happy experimenting!

  5. #2575
    Passenger
    Join Date
    Jul 2016
    Posts
    19
    Quote 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 Images Attached Images

  6. #2576
    Passenger
    Join Date
    Jul 2016
    Posts
    19
    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 at 12:22.

  7. #2577
    Captain abcd567's Avatar
    Join Date
    Sep 2013
    Location
    Toronto CYYZ
    Posts
    2,835
    @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

    .

  8. #2578
    Captain abcd567's Avatar
    Join Date
    Sep 2013
    Location
    Toronto CYYZ
    Posts
    2,835
    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






  9. #2579
    Passenger
    Join Date
    Jul 2016
    Posts
    19
    Great, thanks abcd567!
    Finished installing it on my second receiver, works like a charm.
    Installing it now also on my main receiver.

  10. #2580
    Passenger
    Join Date
    Sep 2016
    Location
    New Bern, NC
    Posts
    21
    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?

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •