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The EASIEST Antenna to build for Six Meters using one piece of RG-58 coax!

Discussion in 'Amateur Radio News' started by VK7HH, Dec 8, 2020.

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  1. VK7HH

    VK7HH Ham Member QRZ Page

    This is a really simple and easy to construct antenna that will get you on the air on the six meter band using only RG-58 coax!

    I needed a quick and simple antenna for my WSPR beacon over the summer season. Enter the coaxial dipole or aka flowerpot antenna!

     
    N2ZDH, PU2OLT, KK4ZDS and 15 others like this.
  2. N1IPU

    N1IPU Ham Member QRZ Page

    Would make a decent portable antenna for 6m. Most likely will give it a go.
     
    KC5HWB and VK7HH like this.
  3. W1YW

    W1YW Ham Member QRZ Page

    I strongly suggest CPVC if available: PVC is lossy at this frequency.

    Here's how the antenna works---

    COAX is a transmission line system where RF current flows in the center conductor. This produces a counter current in the shield which is out of phase. The two cancel in the far field.

    When you expose an electrical quarter wave of the center conductor-the currents become unbalanced and the coax radiates. The short length below the unshielded center section is essential the 'ground' part of a vertical dipole. The multi turns are an RF choke, stopping the coax from radiating below that point. You can use ferrite instead of the coil-choke.

    The fishing line is purely a mechanical strain relief and keeps the coax straight in the tube.

    Build and learn:)
     
    Last edited: Dec 10, 2020
    VK6APZ/SK2022, NU4R, KA0USE and 5 others like this.
  4. VK7HH

    VK7HH Ham Member QRZ Page

    Good and lightweight for SOTA!
     
  5. VE3VXO

    VE3VXO Guest

    How is that simpler than an inverted-vee? Unless you are only planning on using it for repeaters or maybe local simplex what good is it? You would want a horizontaly polarized antenna for Es propagation. An inverted-vee will give you access to both.
     
  6. K0UO

    K0UO Platinum Subscriber Platinum Subscriber QRZ Page

    A simpler way would be/ just Hook the to coax up to two pieces of wire that is cut 54-in on either side of Center and you have a dipole.
    I have even striped the braids back 54-in. Then use a center for one side and the braid for the other, then add some kind of insulator (I have just use paracord in the past) now that's easy.
     
    WA4TFJ and AA5LS like this.
  7. VK7HH

    VK7HH Ham Member QRZ Page

    It's simpler as it uses less parts. You don't need a centre insulator, or extra wire. You do not need a horizontally polarized antenna for Es. Es work just as well on a vertical, there is very little polarization mismatch on Es.
    You can also string this us as a horizontal antenna easily
     
    KC5HWB and KF4ZKU like this.
  8. VE3VXO

    VE3VXO Guest

    "Although polarisation shift can occur, single-hop Sporadic E signals tend to remain in the original transmitted polarisation." Wikipedia link to Es propagation

    So sure you don't need horizontal polarization that's true, but since Es tends to preserve polarization and since most people calling will be using a Yagi array, you might want to have some horizontal polarization if you would like to talk to them. Of course if you really want a challenge, (because 6m Es isn't challenging enough) you could always try to hook up with those other 1% who are using a vertical whip. In that case it will work very well, just as you said.
     
    HB9EPC likes this.
  9. K3FHP

    K3FHP XML Subscriber QRZ Page

    What, no Faraday Rotation?
     
  10. VK7HH

    VK7HH Ham Member QRZ Page

    Proof is in the pudding. I'm hearing 2500km (1500 mile) signals on it right now. Shock, it works! Also, where is the reference that the Wikipedia article is referring? I'd like to look it up
     
  11. M0YRX

    M0YRX Ham Member QRZ Page

     
    NL7W likes this.
  12. KC3PBI

    KC3PBI Ham Member QRZ Page

    I built one of these scaled/tuned for 2m this spring. It worked remarkably well and I learned a lot doing it.
     
    VK7HH likes this.
  13. VE3VXO

    VE3VXO Guest

    That RSGB talk was interesting new information. Thanks for that. It's a lot to claim based on a single 2 minute recording. One thing it definitely proves is that it's wise to choose a thesis topic in an area where nothing can be proven, or disproven for certain. So if we accept the work and its tenuous conclusions then what about the question of a super simple yet effective 6m antenna? Accordingly it should respond to both vertical AND horizontal polarization. Perhaps an inverted vee then?
     
  14. 2E0CIT

    2E0CIT Ham Member QRZ Page

    Excellent instructive video. Thanks!
    Now I want to build one for FM broadcast band and one for DAB.
    I've seen a few of these build videos for 2m, 6m, etc.
    What would be really useful is (anybody got one?) a formula for designing them for any frequency, or maybe it's just a matter of scaling lengths and coil turns empirically from this or other such coax vertical dipole antennas that are known to work??? Would simple scaling work?

    Also, re. velocity factor ..if you surround an antenna with a radome, -plastic, glass, etc, wouldn't you have to cut the metal elements a bit smaller?;)
    73 Jeff
     
    Last edited: Dec 11, 2020
    VK7HH likes this.
  15. KC3PBI

    KC3PBI Ham Member QRZ Page

    I used this page as a guide when I built mine. It includes some other references that can be used to scale the design.

    Because I used common sch. 40 1/2" pvc pipe instead of metric 25mm conduit (and other minor differences) I decided to wind my choke 8.5 turns instead of 9. In theory that gives mine a 139MHz resonance.

    Then I tested it:

    Screen Shot 2020-12-11 at 11.04.55 AM.png
     
    N2ZDH, K1BQY, VK7HH and 1 other person like this.

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