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Sirio GM-ground level question

Discussion in 'CB Antennas' started by gamegetter, Sep 29, 2011.

  1. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    I agree SW.

    I was surprised with the patterns too. The 6" raised model suggest to me that Penn's idea for DX might work just as he notes, even though the gain looks to suffer badly. With that said, I've made some very good long distance contacts with very low watts out, and when conditions were working for me. DX is just unpredictable and depends a lot on how the antenna propagates...with waves combining somehow or not.



    If the ground mounted model is even close to accurate, it would appear like the bottom lobe is out of phase with the top, but far worse than a regular 5/8 wave ground plane. IMO this might account for the very low gain we see reported by Eznec. SW, wouldn't that too be sorta' predictable also?
     

  2. eagle1911

    eagle1911 Active Member

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    Perhaps not optimum, I agree with that, but it depends on the design of the antenna. Typically when verticals are ground mounted it's out of necessity, my case included. I keep mine low and incognito to avoid having neighbor issues and to preserve the curb-appeal of my home. I live in an anal neighborhood.
     
  3. Needle Bender

    Needle Bender ...he thinks it's funny that I stepped in it

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    so the gainmaster is a perfect antenna to mount right on the ground if you live in a canyon or at the bottom of a steep mountain range and need to talk over it:whistle:
     
  4. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    I agree Booty, but I mentioned earlier that Penn did not give us any real details, so we really don't know the height he was talking about. When we hear discussions about ground mounting, I think most are referring to lower HF antennas, a really good ground radial system, and situations similar to what Eagle is suggesting. SW might agree or not on that.

    gamegetter, admittedly I was not as close to the ground as my model here, but I showed you what my GM did at 11'. If you'll look at the SWR bandwidth curve again...the SWR hardly changed. If you do look again, this time look at what happened compared to when I used the analyzer.

    The only difference I can recall from operations of my GM at 11' feet back then, was that I noticed the antenna responses were very attenuated. This is why I have recommend to set your GM well in the clear, and at or above 20' feet.
     
  5. Needle Bender

    Needle Bender ...he thinks it's funny that I stepped in it

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    marconis right. i think youd be better off with a imax or i10k mounting it that low
     
  6. eagle1911

    eagle1911 Active Member

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    An IMAX is what I use. The OP was interested in the GM.
     
  7. Robb

    Robb Yup

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    Well, I can only say what I've heard for myself.

    It seems that every station that I have talked to that ran that GainMaster (including Marconi) had an outstanding signal.

    Most were running them around 30 ft or more.

    The evidence is anecdotal; but consistent . . .
     
  8. Needle Bender

    Needle Bender ...he thinks it's funny that I stepped in it

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    yeah i dont understand these guys who badmouth the gainmaster. its a 5/8 so like other 5/8 it should have a good amount of gain but since its driven in the middle and is all in phaze it can only be better when its high in the sky
     
  9. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    Hey Robb, my GM is at about 39' feet. No radio since June for me. With the heat and no rain for months, everything including signals was dying. Several of my regular buddies, on 39, live in the brush fire areas we've been having in Texas. For them it has been touch and go. We've even had smoke problems here in the big city.

    Just last week, conditions were improving, but still no rain to speak of. It's time for some antenna changing, don't you think?
     
  10. Shockwave

    Shockwave Sr. Member

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    That consistency with good performance is not what we typically see in any other fiberglass stick. The Antron 99 and Imax 2000 can have widely varying results especially with DX from one installation to another. It comes down to them radiating off the mast and coax. This causes many different problems but the most interesting one is in the secondary lobe of the radiation pattern.

    The effects different lengths of coax and mast radiation has on secondary lobe in the A-99 and Imax 2000 can cause DX performance to range from relatively good, to completely crippled. Thankfully the balanced design of the GM eliminates these issues. The first clue that the GM is different is the notable absence of any RFI radiating from the coax.
     
  11. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    SW, I agree. Very good point, and I think you're right. Good idea to remember, and one that I never though about before. I think this sorta' proves Bob85's long standing claim in this regard, and he should love this idea.

    Good to see you out here. Have you talked to Bob lately?

    Thanks!
     

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