Announcement

Collapse
No announcement yet.

best antenna

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

  • abcd567
    replied
    Originally posted by Scroggie View Post
    I've just remade it with a 10 turn, close spaced coil (1.5 mm enamelled wire) and still with 60 mm and 137 mm lengths and that has improved it by about 3dB (using the weakest signals showing on the graphs as a rough guide - see pic attached) I made the change at 18:48 and it does look promising. There are of course very few aircraft around to get the full picture.
    fetch?photoid=184359.png
    thumbs-up.jpg

    Well done. Happy Experimenting.

    EDIT:
    What is the length of your 10 turn "close spaced" coil? My design was16 turns, 53 mm long coil.
    Last edited by abcd567; 2020-04-06, 20:38.

    Leave a comment:


  • Scroggie
    replied
    I've just remade it with a 10 turn, close spaced coil (1.5 mm enamelled wire) and still with 60 mm and 137 mm lengths and that has improved it by about 3dB (using the weakest signals showing on the graphs as a rough guide - see pic attached) I made the change at 18:48 and it does look promising. There are of course very few aircraft around to get the full picture.

    Leave a comment:


  • abcd567
    replied
    Originally posted by Scroggie View Post
    abcd567:
    I had a go yesterday with some 1.5 mm copper wire (I don't have any steel and anyway I wanted to solder it to an F connector)
    Because my wire was so much thicker than yours I have ended up with an outer diameter of 8.4 mm - the drill I wound it on was 5,1 mm
    At first I mounted it in a north facing window and was a little disappointed until I looked at the same direction on my other outdoor antenna/receiver which showed very little traffic to the north of me anyway.
    Today I moved it to a south-east facing bedroom window and now it looks very promising. and this is with a coil of a different diameter! The other dimensions are the same.
    Now is not the time to get a very sensible comparison given that the daily count of aircraft I'm seeing has dropped from 2500 to 400 but considering the difference between the ranges from an 8 element coaxial colinear at 40 feet and your design in a bedroom window I'd say it's very successful. To only see 22 aircraft at what is normally peak time here is truly remarkable.
    Now I need to make another one, weatherproofed and mountable on my ham radio mast!


    Scroggie
    thumbs-up-3.jpg
    Great!
    Congratulations that you made a good wire collinear in first attempt.
    Try to make one or two more with few mm different lengths of lower and upper wires, and see if gives improvement. Make changes one at a time to know its affect. Do not change many dimensions simultaneously. By experimenting with trimming you can get an optimum design for your wire dia and your coil parameters.

    Leave a comment:


  • abcd567
    replied
    Scroggie:
    Software & calculations provide a starting point only.
    Finally it is trial and error, trimming and adjusting the built prototype.
    I built one based on calculation then startted trimming, it improved, then after a point worsened.
    The wire was cut smaller than the length where I got better results.
    I had to make another prototype with longer wire, and started trimming testing, but this time I was aware not to cut too much.
    DIY antennas are "trial and error" and "a shot in dark". Happy experimenting and good luck.

    Leave a comment:


  • Scroggie
    replied
    abcd567:
    My previous post has gone "unapproved" for some reason but I think it will appear eventually.
    In addition to that though I've been Googling coil calculators and found a very good one called Coil64-1.1.7 (Google it - I'm not sure if links are allowed in these posts)
    Anyway, using that software and your wire / dimensions it gives your coil a value of 0.212 microH and mine 0.232 microH. Reducing mine to 15 turns and I get something close to your value.
    Another option using my wire would be 10 turns closely wound (it is enamel coated) What do you think of that idea? - I think it would be more rigid and a little easier to make.

    Scroggie
    Last edited by Scroggie; 2020-04-05, 18:56.

    Leave a comment:


  • Scroggie
    replied
    abcd567:
    I had a go yesterday with some 1.5 mm copper wire (I don't have any steel and anyway I wanted to solder it to an F connector)
    Because my wire was so much thicker than yours I have ended up with an outer diameter of 8.4 mm - the drill I wound it on was 5,1 mm
    At first I mounted it in a north facing window and was a little disappointed until I looked at the same direction on my other outdoor antenna/receiver which showed very little traffic to the north of me anyway.
    Today I moved it to a south-east facing bedroom window and now it looks very promising. and this is with a coil of a different diameter! The other dimensions are the same.
    Now is not the time to get a very sensible comparison given that the daily count of aircraft I'm seeing has dropped from 2500 to 400 but considering the difference between the ranges from an 8 element coaxial colinear at 40 feet and your design in a bedroom window I'd say it's very successful. To only see 22 aircraft at what is normally peak time here is truly remarkable.
    Now I need to make another one, weatherproofed and mountable on my ham radio mast!


    Scroggie

    Leave a comment:


  • abcd567
    replied
    Scroggie:
    I wound the coil on 3/16 inch dia drill bit which is 4.76 mm dia (I do not have mm size bits).
    The wire used is thin steel tie wire, diameter aprox 0.5 mm (see the wire on floor in first photo below).
    I used thin wire as I found it easier to shape, and easier to wound on stud of magnetic base.

    Initially I made length of upper wire more than 137mm and after making, measured SWR by VNA. It was 2.1
    I then bend the tip of wire to reduce length and measured again, and repeated this till I got reading of about 1.57

    Optimized Whip Steel Tie Wire-R.jpg



    Coiled Collinear and Quarter Wave-2.jpg
    Last edited by abcd567; 2020-04-04, 22:02.

    Leave a comment:


  • Scroggie
    replied
    [QUOTE=abcd567;n184155][B]Wire Collinear with Coil & Ground Plane


    (1) SIMULATION: Lower Radiator = 60mm, Upper Radiator = 137mm

    SWR = 1.69
    Gain = 4.98

    Coiled Whip - 60mm lower- Radials 45 degree down.png



    That looks really good - I'm going to make one.
    My colinears have been very successful but I have no way to do the detailed analysis of them that you clearly do so this would be an excellent antenna to do comparisons with.
    Just one question if I could. Your coil diameter is 5 mm - hopefully that's the internal measurement, ie was it wound on a 5 mm rod / drill bit?. I was planning using 1.67 mm diameter copper from the inner of some co-ax I have so if it's the outer diameter it would need to be wound on a 1.66 mm drill which wouldn't be practical.

    Scroggie
    Last edited by Scroggie; 2020-04-04, 10:23.

    Leave a comment:


  • petercr
    replied
    2 here on a Saturday morning when there would usually be 25-30
    4th April Virtual Radar Capture.PNG

    Leave a comment:


  • Scroggie
    replied
    This is at a time when pre-coronavirus there would normally be 150 - 170 aircraft in range!

    Leave a comment:


  • petercr
    replied
    My plane count is down to about 1/3 of what it normally is but with cargo still flying between China and New Zealand, I'm still seeing close to my normal Max range...

    Leave a comment:


  • abcd567
    replied
    Wire Collinear with Coil & Ground Plane


    (1) SIMULATION: Lower Radiator = 60mm, Upper Radiator = 137mm

    SWR = 1.69
    Gain = 4.98

    Coiled Whip - 60mm lower- Radials 45 degree down.png


    (2) SWEEP- lower radiator length vs SWR


    Coiled whip - Lower wire length vs SWR.png



    (3) SWEEP- lower radiator length vs Gain

    Coiled whip - Lower wire length vs Gain.png
    Last edited by abcd567; 2020-04-02, 23:18.

    Leave a comment:


  • abcd567
    replied
    Wire Collinear With Coil & Mag-mount Ground Plane.

    Note: Because of extremely reduced number of flights due to covid19 epidemic, the difference between two whips is not glaring in the graphs. I will re-test after flights are normalized.

    Coiled Collinear and Quarter Wave.jpg

    .

    Coiled Collinear - SWR - R.jpg
    .


    coiled whip - aircraft-R.png

    .

    coiled whip - range-R.png
    Last edited by abcd567; 2020-04-03, 14:14.

    Leave a comment:


  • wiedehopf
    replied
    utack:
    It depends on what your obstacles are.
    ADS-B/1090 MHz is line of sight, so you need a clear line to the aircraft you want to receive (clouds don't count, trees significantly reduce range in that direction)
    https://forum.flightradar24.com/foru...-get#post89878

    Leave a comment:


  • petercr
    replied
    Kind of antenna related - got up on the roof this morning and replaced 3x 5m sections of what looked like RG196 coax (with a 15cm N-SMA stub) with 1x 15m length of pre-terminated LMU400 coax and my range is now in excess of 220Nm to the N / NE plus about 20% better than previous to the E & S / SE.

    Leave a comment:

Working...
X