Friday, December 23, 2011

Antenna experiment - Fractal Quad for 28 Mhz band




Fractal Quad antenna - support made of PVC tube & fittings


Fractal Quad antenna prototype


Fractal Quad Antenna - measuring SWR and resonance frequency




NEC2 model of Fractal Quad


Fractal Quad - Nec2 model 3D

NEC2 model -  azimuth

NEC2 model - elevation


Fractal Quad prototype



So what did I learn about this small scale antenna experiment? 





73  de  Mauri  AG1LE


  1. 73 from old timer in the 60s. Hey, I'm a journalist (old one) and doing research on something "found" in china. I'd attach jpg file if you get in touch. No, it's not the famous puzzle thing in the news lately... something quite different and remarkable. And for what use... can we talk? is the web site, myristicin-at-hotmail-dot-com... Gary Vey

  2. I am interested in building one please contact me Gary.

  3. Wow! Very cool. The look of the antenna reminded me the orthodox crosses (hi):

    One question - is this antenna smaller than a normal quad with circular full wave elements?

    Thank you,
    Paul VA3PAW

  4. Hi Paul

    Yes, the dimensions of fraqtal quad are smaller than normal quad. That is one of the benefits of this antenna design.

    Mauri AG1LE

  5. Is it possible for 3,75 mhz?

  6. With PVC pipe as support and methods described above fractal quad would be too large and fragile at 3.75 MHz band.

    If you can figure out more robust support structure you could scale the antenna to that band.

    Let me know if you decide to pursue this.

    Mauri AG1LE

  7. I noticed you used a Sierpinski fractal 'curve' for your elements. Any ideas on other fractals and their merit for antenna work?

  8. Hi
    I haven't tested other fractal shapes. Chip Cohen W1YW might be a good contact to ask this question. The shape I used was easy to implement, no special tools was required and parts can be found from regular hardware store, like Home Depot.
    I recommend doing some experiments and publishing your results. There are many speculative posts in different forums but not many articles with concrete results, especially for HF antennas.
    Mauri AG1LE

  9. It looks like you are using the grey pvc conduit pipe. Just wondering how it holds up to the weather. I am using it in my 2 element 6 meter quad.
    Thanks 73s Dan KC2YTI

  10. Bonhomme de jour.
    Dans ce cas, je peux construire une fractale pour la gamme de 40m sans problèmes, alors je vais devoir prendre soin dans le choix le plus approprié des matériaux de renforcement...
    PY5KYW - Marcelo

  11. Bonhomme de jour.
    Dans ce cas, je peux construire une fractale pour la gamme de 40m sans problèmes, alors je vais devoir prendre soin dans le choix des matériaux les plus appropriés pour corriger renforcement structurel?

    Forte de 73 à leurs collègues.

  12. @Marcelo - I used Google Translate since my French is rusty ;-).

    > Bonhomme day.
    > In this case, I can build a fractal for the range of 40m without
    > problems, then I'll have to take care in choosing the most
    > suitable reinforcing materials ...
    > PY5KYW - Marcelo

    Yes - the 28 Mhz prototype support structure was made with cheap PVC pipe that is not very strong.
    You need to use much stronger materials if you want to scale this to 7 Mhz band.
    I used #14 insulated copper wire that is also quite soft and bends easily.
    You may want to consider using aluminum or some stronger material for elements.

    Good luck and can you take some pictures if you decide to build fractal antenna for 40 m band?
    That would have some novelty value as I have not seen anybody building a fractal quad for that band.

    Mauri AG1LE