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4 - ELEMENT QUAD HELP NEEDED

Discussion in 'CB Antennas' started by unit_399, Sep 2, 2014.

  1. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    Henry.....I think I see where you misunderstood my intentions and what it was I said. In the quote below I was assuming the design of 399's quad was a basic everyday common quad design and is the reason I said most of the current is in the driver element. I still stand by that.

    Next I said :"Any antenna I have seen has the most RF current in the driver element and first director with negligible current in the reflector and further directors." which I also stand by. I have known that there are times the first director can have more RF current in it than the driver element. I have such an antenna that I built myself. My six element 6m yagi is built like this based on the OWA. This is it on the bottom.Notice the spacing which is similar to the second current plot on this site. http://www.qsl.net/dk7zb/DK7ZB-Match/theory_28ohm.htm

    IMG_2221.jpg



    You stated "Besides that first director, there are antennas where other parasitic elements have the highest amount of current.
    So to your last question asked...yes there are."
    which is what I was asking for an example of......an example of an antenna where the most current is in an element OTHER THAN the driver OR the first director.
     

  2. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    Old vertical I had Cushcraft R8 I believe used parasitic coupling? (correct term?) to cover the multi band vertical. I thought the antenna was a great dummy load. Gave it away.

    QST had an article of putting a 6 meter parasitic driven element in front of the driven element on a tri bander, so it could cover 6.10.15. and 20 meters.

    Still this is sort of what the discussion is about ( not the topic of the thread.) Another element having more current than the driven.
     
  3. Mudfoot

    Mudfoot Sr. Member

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    Wish I was the one u gave it to.
     
  4. wavrider

    wavrider W9WDX Amateur Radio Club Member

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    Mudfoot gave it to a General class ticket holder next county South of me. He was wanting to get on the air and had a small lot.
     
  5. unit_399

    unit_399 EL CAPO

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    Thanks for all the replies and info. I asked the original question because I have lost two antennas to wind, and I don't want to lose a third. I was thinking that since the diameter of #16 wire is about half that of #10, that using #16 on the parasitics would improve the antenna's aerodynamic efficiency. I know we're not talking a mega-improvement here, buy every little bit helps. Right ??
    We live at the top of a mountain that overlooks a 1o km long valley. The valley is wide at the other end, but narrows considerably at the base of our mountain. Because of this venturi effect, a strong breeze at the other end of the valley becomes a major blow at our end. When my quad came down, the wind gusts were so strong that they snapped one of my #10 steel guy wires. and my guadua tower broke at the base.
    This thread has evolved into a theory discussion, and I would like to ask: What is the percentage difference in the rf current flowing in the driver vs the current flowing in the director?? Is the director current 1% of the driver current? 10%? or ...?? Just wondering. 73S.

    - 399
     
  6. Henry HPSD

    Henry HPSD 19DX348

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    Hello,

    Sorry it took me a bit longer, had 3 exams last week, but the most important thing :
    I picked-up a president adams VFO last nigth, just so happy with that last one !

    Anyway...Tnx for the clarification CK !

    @ 399.
    The amount of current variees.
    Sometimes the current can be more than the driven element, although this is not often the case.
    For you to get an indication in percentage's...
    Roughly very roughly you could say : dropping till about 30 percent of the main radiator.
    The amount of current and the equal progressive phase shifts are responsible for the antenna its pattern.

    One cant say those currents are neglible, as each individual element has its contribution in all parameters of a beam
    Although it is true that not all will have the same effect.
    Logical: as adding a reflector to a dipole will have a lot more effect compared to adding the 19th director to a 18 element beam.

    For the average CBer those currents arent really interesting...well...perhaps you have seen that "sticker" : watch out high voltage on a antenna.
    Thats probarbly as close as many cbers will come to that subject.

    However, there are others...
    The best example i had was with one of those super bowl guys.
    He had a 50 ohm OWA yagi, but could hear noises comming from the director when applied full power.
    The antenna became unstable. (not talking about a couple kw anymore).
    He was thinking of thicker diameter, logical...but we also redesigned his present beam.
    Reducing the amount of current on that first director...problem solved !
    The example CK an I were referring to a OWA yagi and its current can be seen at the bottom of this page:
    http://cb-antennas.com/?page_id=745
    In that case the current of director nr 1 AND director nr 2 have about 1,2 times the amount of current exsisting in the radiator.

    Without playing “tricks” an example could be this one:

    This is a 6el “V-yagi” based on a original idea from k6sti
    In this case the amount of current in director nr 3 is highest.
    [​IMG]


    But there are many more..
    Examples can be found on martyn his website:
    (search for that V yagi or U yagi from UA9TCetc)

    Hope it was of use...

    Kind regards,

    Henry
     
    unit_399 likes this.
  7. nosepc

    nosepc On Vacation

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    Hello,

    I would look for resonance boxes with GRID-DIP, only tool that can tell us the real resonance.
    The problem is that changing the resonance of some changes the other by proximity.
    As for the parasitic elements, are given more importance than they actually have.
    These add little after the 3rd element, and actually earn much more by adding another antenna 3 other elements, making a 15-item, since they really emit and receive the rf are the radiating elements. Truly dedicated antennas, such as radar used collinear formations, also to the formation of GSM telephony, etc.
    This we have found making collinear antennas VHF and UHF policies, which did not differ much from the radar "FREYA" Wermatch in the 2nd war.
    For this reason, Y prefer a Swiss Quad antenna in CB band.
    Regards.
    Ernest
     
    #22 nosepc, Sep 6, 2014
    Last edited: Sep 6, 2014
  8. The DB

    The DB Sr. Member

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    I see, throwing out another obvious untruth trying to get someone to bite... Go figure...

    For the record for everyone who lives in the real world, modern day antenna analyzers, even the cheap ones, are more accurate than grid dip meters ever were, as long as they are in spec. A VNA, or Vector Network Analyzer, is typically far more accurate than anything using the technology of a grid dip meter could ever hope to achieve. Hell, I could use an oscilloscope to get a resonance reading at least as accurate as any grid dip meter. If they were really the only truly accurate device they would not have fallen out of use to begin with...

    This is coming from someone who actually owns a grid dip meter... Every now and then I use it on an antenna, namely for kicks, or if someone actually has an interest in the device or learning about antenna theory. Especially the history of antenna theory, it is good to know where we came from to understand why what is, is...


    The DB
     
    wavrider likes this.
  9. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    Not many of us left that still use a grid dip meter any more. I used to have an Eico dip meter but it died and I trashed it years ago. I picked up an old James-Millen dip meter several years ago and it works great. Like you, I still play with it a bit but that's just all I do....play with it to keep in practice. I usually use my antenna analyzer for field tuning.

    I just wondering what kind of "resonance boxes" nospec is looking for with a grid dip meter. A tuned cavity perhaps?
     
  10. nosepc

    nosepc On Vacation

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    Well confuse an antenna impedance analyzer with the resonance frequency is common in novices.

    Also called "antenna tuners" to transmatch or couplers transmission lines, because they are very different things.

    You are excused, whether they are consumers of plastic bags, the penalty is if your brain is inside of them.

    Greetings to everyone

    Ernesto
     
  11. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    I see by the condescending remarks your attitude still has not changed. Let's see how far this one goes before the feces strikes the rapidly rotating blades of the air movement device. I'll set it to high and plug it in now. :whistle:
     
  12. bob85

    bob85 Supporting Member

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    sorry i just have to lmfao@CK

    im one of the guys that own a grid dip meter but very rarely use it anymore.
     
  13. The DB

    The DB Sr. Member

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    Trying to call me a novice? Well, compared to some on this forum that may well be true, lets see if I am a novice compared with you... I'll use the post I'm quoting from as an example...


    First off, antenna analyzers are NOT called antenna tuners or transmatches, never were, never will be. They are two very different things. An antenna analyzer will analyze the antenna system and give you the complex impedance (at least to some extent, antenna analyzers like the MFJ's have no concept of a negative X or phase angle). An antenna tuner, or transmatch, is used to modify the impedance of the signal between the radio and the antenna so the radio has a low SWR at its feedpoint, and the antenna is fed with (or at least close to) a conjugate match. You say they are the same yet any novice, and anyone else really, can easily tell you otherwise...

    Your argument of me being a novice isn't looking so good is it...


    You throw this insult as well as call me a novice in the same post that you demonstrate something that even a novice has a better understanding of than you? If I am a novice then you rate below someone who knows nothing about antennas and knows it... Actually, that is true no matter what my rating happens to be...

    You are nothing more than a troll.

    Have a nice day...


    The DB
     
  14. nosepc

    nosepc On Vacation

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    (n)

    A VNA can indicate the approximate resonance frequency of an antenna, a GDO gives the exact frequency.

    In the case of the cubical quad antenna, GDO use if you want it to work properly as it is a very narrow band antenna. The VNA indicates the impedance, and a frequency around.. But there is still people who believe that when an antenna is resonant impedance is 50 ohms, and that's a mistake, because each has a different antenna impedance, according to its design, fitness, nearby items etc. But beyond them ..

    A cubical quad antenna has a 100 ohm impedance at the feed point, which means 2: 1 and SWR is correct !!
    However, the novice would reform the antenna up to show 1: 1, removing the antenna resonance, just to satisfy your S: W: R meter and VNA, and misconception of what is resonance, impedance, couplings, etc.

    Regards.
    ernesto.
     
    #29 nosepc, Sep 9, 2014
    Last edited: Sep 9, 2014
  15. The DB

    The DB Sr. Member

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    So you are saying that a VNA is only approximate? I would love to see your source for that data, but as usual you have nothing because nothing exists... There are, however tests available online that compares the accuracy levels of VNA's, and the ones tested are accurate far beyond any grid dip meter...

    I can also tell you that a the part of the Grid Dip Meter where you choose the frequency is an approximation to within a certain limit at best. Its the nature of how the devices work, and a function of the dated technology within them. I can tell you from personal experience, and if you owned one and a VNA you would know that to be true as well. I guess you don't do you...


    I have news for ya, the CB band, at least here in the states, takes noticeably less bandwidth than a cubical quad has... If you still want to try and claim that a cubical quad has less bandwidth than the CB band, I'll simply use your favorite dated modeling software, you know, the one you swear by, to prove you wrong yet again. Of course, you will ignore that, just like you ignore every thing posted by me and others that proves your stories wrong time and time again...


    So you realized that a cubical quad has a natural SWR near 2:1... I am curious as to why you brought up such a well known fact and assumed that someone like me. I, personally, would simply use an electrical half wavelength of 75 ohm coax as an impedance transformer to keep the radio happy. That is all I care about SWR for, by the way, and you should know that by now. If I wanted I could very easily tell you any number of other ways to do the same thing if you wanted.

    You do know you are talking to someone who could really downplays SWR readings right? Someone who has, on more than one occasion in the past made the case that SWR meters make you stupid? I guess you have been ignoring the useful data from me and others as usual...

    Answer me this, why does the MFJ grid dip meter cost about half of what their cheapest antenna analyzer costs if it is so much better? Why is no one beating a path to their door to buy their grid dip meters but they are to buy their antenna analyzers? An antenna analyzer that is very low end compared to a VNA, which typically costs twice the price again and often more? Why is there a need for such other far more expensive devices when you can get a grid dip meter at such a low price? Why do modern day broadcast engineers not use grid dip meters anymore if they are so great?

    You continue to use your dated technology that everyone who knows anything, including novices, has no hope in the real world of matching even a cheap analyzer, much less a VNA, that can not only accurately determine not only resonance, but reactance and impedance as well, as well as many other properties. Actually, I want to see a picture of your grid dip meter...


    The DB
     

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