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Thread: Well, I finally figured it out

  1. #1
    Orca Whisperer
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    Well, I finally figured it out

    So, the attic antenna I currently am using (Which is a "fan dipole", multiple tuned elements fed at a common feed point) is still running. No fire in the house yes, and my leads have not melted, even when putting out 100W or so via a tune.

    But, since this "dipole" is not really lain out in "dipole fashion" (It's in the shape of a "V" almost), it's lain out as such:

    Code:
                                   |       <----  Feed line
                                   |
                                   ^      <----  Feed point
                                 /    \
                                |      |
                                |      |
                                |      |
    
                                |______|
                        About 25ft separation between sides
                        And, at ends, 10ft or better separation of each element
    I've always wondered the directivity. Is it like a dipole? If so, end-fired of which "side"? One direction, or two?

    Turns out, it's directional. It's fires off of one side. So, my challenge over the next few weeks or so is to model this thing in EZNEC, so I can play with some items.

    PSKReporter is a really good tool when trying to figure out your lobes and what not :)
    Big Giant Meteor 2020 - We need to make Earth Great Again

    http://www.coreyreichle.com

  2. #2
    "Island Bartender" KG4CGC's Avatar
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    Do you have a device you can rig up to test field strength? Key up at the lowest power setting and test it on different bands to get an idea of the type of pattern you are getting.
    I had an article somewhere that detailed how to attached a very simple home brewed device to a DMM for use as a FS meter.

  3. #3
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    Quote Originally Posted by KG4CGC View Post
    Do you have a device you can rig up to test field strength? Key up at the lowest power setting and test it on different bands to get an idea of the type of pattern you are getting.
    I had an article somewhere that detailed how to attached a very simple home brewed device to a DMM for use as a FS meter.
    Hm... I should give that a whirl. I'm sure a tuned coil attached to a DMM can suffice as a FS meter. I also have a radio shack 3-30MHz FS/SWR meter that says it can be used as a FS meter (I have my doubts).
    Big Giant Meteor 2020 - We need to make Earth Great Again

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  4. #4
    "Island Bartender" KG4CGC's Avatar
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    I guess you already know, the lower the power setting the better. Attenuate the feedline maybe??? To keep the readings within walking distance LOL!

  5. #5
    SK Member (12/16/2011) W3MIV's Avatar
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    Judging from your diagram, it is hard to see how it could work without significant interference of one element with the other. Just because an antenna "loads" does not mean it radiates well, or even much at all. A good deal of your power could be heating up the ground.

    If you ever want to try a practical test, I will be available just about any evening you choose -- except tonight: On Tuesdays I hold a regular bullseye pistol match and tonight I also have a gun club meeting. Any other time, however, I will be happy to give it a shot. PM or email me as you like.
    73 de Albi

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    "We only become what we are by the radical and deep-seated refusal of that which others have made of us." --- Jean-Paul Sartre.

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  6. #6
    SK Member (12/16/2011) W3MIV's Avatar
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    BTW, if you want to attenuate the antenna, I have a pin you can borrow.
    73 de Albi

    Veritas vos liberabit!



    "We only become what we are by the radical and deep-seated refusal of that which others have made of us." --- Jean-Paul Sartre.

    "Who controls the past, controls the future. Who controls the present, controls the past." --- George Orwell.



  7. #7
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    Quote Originally Posted by KG4CGC View Post
    I guess you already know, the lower the power setting the better. Attenuate the feedline maybe??? To keep the readings within walking distance LOL!
    Thinking maybe a series resistance in the feedline? I dunno. I may have to work it at 5 watts (Should be noticeable at that level).

    Quote Originally Posted by W3MIV View Post
    Judging from your diagram, it is hard to see how it could work without significant interference of one element with the other. Just because an antenna "loads" does not mean it radiates well, or even much at all. A good deal of your power could be heating up the ground.

    If you ever want to try a practical test, I will be available just about any evening you choose -- except tonight: On Tuesdays I hold a regular bullseye pistol match and tonight I also have a gun club meeting. Any other time, however, I will be happy to give it a shot. PM or email me as you like.
    It get's out subjectivley well. PSK reporter routinely shows me hitting the entire US (Short of PA, NY, and OH, that's because I'm "shooting over" them). I heard KB6JSO a couple of days ago, and I at times, hit Europe.

    But, you're point of heating up worms is most likely true. It's cut for 40-20-10 meters, and for 20 and up, it's nowhere near 1/2 wave above ground. I was interested in how this antenna worked, since I knew it was "sub par" in it's layout. I think the only saving grace is it's in the attic, and I have a near metal free environment up there.

    Quote Originally Posted by W3MIV View Post
    BTW, if you want to attenuate the antenna, I have a pin you can borrow.
    Big Giant Meteor 2020 - We need to make Earth Great Again

    http://www.coreyreichle.com

  8. #8
    Conch Master W5GA's Avatar
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    Corey, have you ever thought about using an inverted L? Usually seen on the low bands due to space constraints, but no reason it won't work on the higher bands if you have space issues.
    When the government's boot is on your throat, whether it is a left boot or a right boot is of no consequence. — GARY LLOYD

    The nation we live in is the nation we have built by design, each successive generation raising the wall of tyranny a little higher. - Chris Griffin

  9. #9
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    Quote Originally Posted by W5GA View Post
    Corey, have you ever thought about using an inverted L? Usually seen on the low bands due to space constraints, but no reason it won't work on the higher bands if you have space issues.
    It's my next one :) I just have to figure out where to place it. My landlord/neighbor downstairs is also a ham, so I have to try and keep a bit of distance between antennas. And, he has an inverted V for 40M up too :)
    Big Giant Meteor 2020 - We need to make Earth Great Again

    http://www.coreyreichle.com

  10. #10
    Conch Master W5GA's Avatar
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    Cool! Just remember that you want as much of it vertical as you can get.
    When the government's boot is on your throat, whether it is a left boot or a right boot is of no consequence. — GARY LLOYD

    The nation we live in is the nation we have built by design, each successive generation raising the wall of tyranny a little higher. - Chris Griffin

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