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tuning a 6m band Ringo antenna

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by VK6YSF, Aug 16, 2019 at 12:12 PM.

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  1. VK6YSF

    VK6YSF Ham Member QRZ Page

    I have just rebuilt an old 2m Ringo antenna for 6m with all dimensions being consistent with a 6m band Ringo and while the antenna tunes up reasonably well it a appears very deaf. I'm wondering if it is possible to tune the matching ring so as to get a low SWR, but create some sort of self resonance that only makes the antenna appear as a good match.

    Hope this is clear. and keen for any thoughts.

    See link for antenna details. http://vk6ysf.com/ringo_antenna_6m_band.htm

    Regards
     
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    It appears you didn't follow the Cushcraft AR-6 design; did you download the AR-6 manual to see what they did?

    The 6m Ringo uses an open-end coax stub as a fixed capacitor across the feedpoint, etc.

    Of course the Ringo is a modified J-pole design where instead of making a vertical "J" that wastes a lot of space, they just wrapped the transforming section around the bottom as a tapped loop; both designs suffer poor common-mode rejection, so the length of conductive mast and the length of the coaxial cable used to feed them are part of the antenna. It's possible to have a "bad" length of mast (if it's conductive) and/or a "bad" length of coax which will still allow a great SWR but since they are part of the radiating system some lengths create cancellation while other lengths might provide enforcement.

    The design (like the J-pole) really needs a choke balun right below the feedpoint and either be isolated electrically from the mast or used with an insulating mast, although certain "tuned mast lengths" can work well.
     
    K0UO likes this.
  3. VK6YSF

    VK6YSF Ham Member QRZ Page

    Yes; you are right, however I have seen a lot of home brew Ringo antennas for bands such as 10/11m without the coax stub, so figured it may not be necessary, could be wrong.
    Also agree about common mode issue with is antenna and have included a chocking balun. See link; http://vk6ysf.com/balun_choke_balun_low_vhf.htm

    Looks like I will have to bring it down and include the coax stub.........

    I was also wondering if there are more than one taping position on the matching ring?

    Cheers
     
  4. LA3RLA

    LA3RLA Ham Member QRZ Page

    Maybe it is a form of J-pole. I think it is not only a tranformer with tapping, but a paralell tuned coil. A part of the capacity is between antenna rod and the bottom pipe. If it is not enough you must add more capacity. I think it is deaf because it is not in resonance.

    I want to make some 6m antennas and find which has the best radiation. J-pole, EFHW with untuned tranformer, EFHW with paralell tuned transformer, ringo and 5/8 antenna. Why so much work? Some fun and curiosity, but most to find det best antenna.

    My 20m EFHW works 3db better with L-match than with untuned ferrite transformer. The analyzer said all good and resonance, but the practical radiation...

    I looked at your page yesterday and find diameter for each band. I need antenna for 6m, 4m and 2m, maybe I end up with paralell dipols.
     
  5. WA7PRC

    WA7PRC Ham Member QRZ Page

    You are wrong. An end-fed /2 radiator presents a very high impedance (theoretically, infinite). In practice, in the 1-2K range. A tapped inductor (autotransformer) can be used to couple it to a Lo-Z feedline. The tapped ring does that. However, the inductance of the ring needs to be resonated with a parallel C:
    [​IMG]
    Cushcraft used coaxial cable (about 30pF/ft) to do that. It appears they used 7" of RG-11/U (pn 13-AR6-TS, link). The ring on my AR-10 is the same 13" diameter but, the stub is longer (16⅝") to resonate on 10m.

    I didn't care for the cheesy aluminum connectors and other items, and made some modifications to make it mechanically more stout (link). :)
     
    NH7RO likes this.
  6. K0UO

    K0UO Subscriber QRZ Page

    Yes they can be tuned, the two meter version actually has adjustable screws that you can move around
     
    Last edited: Aug 18, 2019 at 3:15 PM
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    So do the 6m and 10m versions.

    But tapping the ring alone, like on the 2m model, doesn't work on the 6m or 10m model -- it needs the capacitor, which is formed by a stub of coax.
     
    NH7RO likes this.
  8. WA7PRC

    WA7PRC Ham Member QRZ Page

    I found a discrepancy in the BOM for the AR-6. The info on the website sez the stub is made from RG-11/U (about 16pF/ft) but, the grainy manual sez RG-8/U (about 30pF/ft). o_O
     
    NH7RO likes this.
  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Good point.

    I actually have an AR-6 and built it per instructions and it works fine.

    I don't recall the coax used, but do NOT recall a small center conductor like RG-11 has, so I'm pretty sure it was RG-213 (50 Ohm) sized. The stub it came with is so short I'm not sure it had a printed designation on it; cutting from a spool it would be luck of the draw whether it's printed or not on a short length.

    The C required can likely be calculated, and the coax stub replaced by a doorknob cap or something...coax is cheaper, which is I'm sure why they used that!
     
    NH7RO and WA7PRC like this.

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