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Thread: Imax 2000

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    Owner Post Founder Of The Radio Room Owner Response



    Imax 2000

    Ok..I have had several people ask me about this so I figure why not get other opinions on this as well so that it can just be read here..

    For people that buy a imax 2000 should they buy and run the ground plane kit or just make a ugly balun for it or run both the ground plane kit and a ugly balun..
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    IMHO, forget the GPK, the 6 ft. radials aren't the proper length to be effective. Add the coiled coax as a choke for CMC's at the feed-point and be done with it. I have one up with neither the GPK nor the choke using Belden 9913 coax and have to intentionally go out of my way and make a concerted effort to deliberately come over anything. The A-99 the IMAX replaced performed the same way. YMMV.
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    I second that, in my experience the GPK makes absolutely no difference at all. Stick that bad boy up and get to talkin!!
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    Just a FYI... I have tried the 45 degree, 6 ft. radial GPK with an A-99 on two different occasions in the past and the ONLY difference I ever noticed was "MAYBE" a very slight difference in the shape of the SWR curve with the GPK versus without. As in, "I really can't be certain if there's a difference or not, but damnit I spent time on this project and I'd better see some change for my efforts or I'm really going to be pissed."
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    No mather how you are going to put it...its a unbalanced vertical antenna.
    With that comes commen mode currents.
    Those can "effect" lots of things...or "wont"...

    Its a bit like a safety belt...you dont need it...untill...

    So..without a doubt the antenna will have commen mode currents (CMC) ...the issue is: where do they go ?...
    That current can travel back on the outer shield of the coax ....or on the mast etc.
    If you place a RF choke directly underneath the antenna and there is no other path a choke can actually do "harm".

    So..what is best.. ?
    If there are some form of radials (they dont need to be long) the CMC can go there..
    .a choke can then be placed directly underneath the antenna.
    Ending in a relative overall "oke" system.
    If you dont have radials on the Imax..place the choke say a feet below the antenna and its fine too...

    ps...in general..a change in SWR is often a good indicator there is CMC present...(but radials on the imax will also effect SWR).

    in short...: create room for CMC ...either with radials or by placing the choke a bit lower...and your have applied your CMC awareness hihi.
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    That antenna has room for CMC built into its design. The mounting tube is meant for that. Inside said tube is two feet of coax. Below that this antenna works best with a proper choke and an isolated mast. The a99 is the same way.

    A radial kit with downward angled radials, even shortened angled radials, will push more signal to a higher lobe as downward angled radials have some small vertically polarized RF, and on an imax that will be out of phase with the upper radiating element. I doubt you would notice the difference though...


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    Owh..didnt realise that..
    You just gave me the another positive thing about the antenna.

    Choke it at the bottom..and ur fine then ! ...

    Agreed on the radials...

    I do wonder however if one good choke is "sufficient"..or that several are needed (at distances)..
    Though thats allready ehm..searching for issues ?
    We can always complain about something...hihi
    Last edited by henryhpsd; 02-05-2016 at 04:26 PM.
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    i had many fiber glass coated antennas starting from the old model big stick to a few imax. i love these antennas for one reason trouble free once up if all is tight it will work for many years from 10 meters to 15 meters with an antenna tuner.
    i had never needed a GP kit. ( i think that is a scam) one winter the mast came loose the antenna hit the roof in an angle and the top half broke off i went to 20 meters tune my swr down to 1.2 and still made many contacts into Europe with 30 watts. is an excellent antenna for the money.
    antenna don't need ground radials or a GP kit. it won't hurt to installs these items but why waste money!
    Last edited by peterwo2e; 10-24-2017 at 01:06 PM.
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