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Re: [30MDG] 30/40 Meter Arrays, Status

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  • David Cole
    Hi, Thank you! The rains have returned with a vengeance here for now... I expect a few more days of rain, (should make the ground soft for radial, and
    Message 1 of 7 , May 16 10:00 PM
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      Hi,

      Thank you! The rains have returned with a vengeance here for now... I
      expect a few more days of rain, (should make the ground soft for radial,
      and cabling), then I'll start the next phase, of getting Feed lines in
      conduit, and radials down for Antenna #1. Once #1 is running fine, I'll
      install #2. Same steps, and that should finish the 40 meter portion...
      I am a bit worried about my GAP sitting just under 1.4 wave away... If
      it gets it the way, I'll move it... :)
      --
      Thanks,
      Dave
      For Amateur Radio equipment reviews and setups see:
      http://www.nk7z.net



      On Thu, 2013-05-16 at 17:34 -0700, W. J. Karle wrote:
      >
      >
      > Dave:
      >
      >
      > Thanks for your reply.
      >
      >
      > The installation layout and your plan regarding when to stop laying
      > radials both seem correct.
      >
      >
      > Someone mentioned concerns about BCI/TVI to nearby neighbours but I
      > imagine that should be less of a problem than heretofore since not too
      > many receivers are operating with 7 and 10MHz IFs (or a harmonic
      > thereof), although some do.
      >
      >
      > I have not run the curves but I wonder if neighbors' RF exposure will
      > be below the published limits.
      >
      >
      > We all will be following your path to success. Good luck.
      >
      >
      > 73,
      >
      >
      > Bill
      >
      >
      > ------------------------------------------------------------------------------------------------------
      > W. J. (Bill) Karle, VE4KZ
      > Radio Amateurs of Canada -- Maple Leaf Operator Member
      > Amateur Radio Emergency Service -- Certified Emergency Coordinator
      >
      >
      > ______________________________________________________________________
      >
      > From: David Cole <dave@...>
      > To: 30MDG@yahoogroups.com
      > Sent: Tuesday, May 14, 2013 9:39:01 AM
      > Subject: Re: [30MDG] 30/40 Meter Arrays, Status [1 Attachment]
      >
      >
      > Hello Bill,
      >
      > I got lucky... The lot is long and narrow relative to itself, close
      > to
      > a 5:1 ratio... The lot is about 300 feet long, and about 60 feet
      > wide,
      > so I can just get radials in place for both a 30 meter four square,
      > and
      > a 40 meter two element. Enclosed is a scaled map showing the antenna
      > locations on the lot, and the radials needed, to scale. I have also
      > added an image called "Array Context", showing the area for about 1/2
      > mile around my home. As you can see, I am on the edge of a huge open
      > area in the middle of a town... As I said, I got very lucky. My lot
      > is
      > defined by the "A", from Google.
      >
      > In the areas where the radials will be slightly short, (maybe 3 or 4
      > feet short), I am not going o worry about them... As far as I can
      > tell
      > from about two weeks of heavy research, this will not make a major
      > difference. The return currents on the radials are highest close to
      > the
      > antenna, and get lower as you go further out, so the effect of
      > slightly
      > shortened radials "should" not be an issue.
      >
      > It strikes me that a few shortened radials, while definitely making a
      > difference, will be so small a difference so as not to worry about. I
      > do worry about the pattern distortion though, but am not smart enough
      > with EZNEC yet to be able to model the arrays, and one takes what one
      > can get... In my case, I have been lucky so far...
      >
      > I intend to lay out radials until I get only small changes in R for
      > each
      > doubling of radials, as measured using an MFJ-259B... I will install
      > the antenna and follow these steps:
      >
      > 1. Take a R measurement.
      > 2. Double the radial count.
      > 3. Take another R measurement.
      > 4. If difference between last to R measurements is something small,
      > then go to 6.
      > 5. Goto 2
      > 6. End
      >
      > As you can tell I used to program, and I find that it helps to
      > formalize
      > the steps being taken. In step 4, when I start approaching a less
      > than
      > 10% change, as I approach 36 Ohms, I will start thinking about
      > stopping.
      > Once I get close to 36 Ohms... I'm done with radials...
      >
      > If for some reason I get lazy, I will put a lot of shortened radials
      > in,
      > as opposed to a few longer radials. Studies indicate that many
      > shorter
      > radials are better than a few long ones. This is caused by the return
      > currents being highest near the base of the antenna, so more radials
      > are
      > more effective than a few long ones. I will not get lazy though, I
      > want
      > as perfect an array as possible for a ground mounted array, the
      > thought
      > of elevating the array, and having 10 or so radials did cross my head,
      > but only for a moment...
      >
      > I will be taking out my trusty RF Ammeter to look at each antenna
      > after
      > the radials are in place... I want to insure the same power in each
      > antenna.
      >
      > If you have any thoughts on this, good, or bad, please let me know
      > sooner than later... That goes for anyone looking at this... I would
      > much rather change plans prior to radial layout, than post radial
      > layout.
      >
      > I purchased two miles of wire for the radial field... :)
      >
      > See:
      > http://www.ncjweb.com/k3lcmaxgainradials.pdf
      > and
      > http://www.antennasbyn6lf.com/files/antenna_ground_system_experiment_2.pdf
      >
      >
      > --
      > Thanks,
      > Dave
      > For Amateur Radio equipment reviews and setups see:
      > http://www.nk7z.net
      >
      >
      >
      > On Sun, 2013-05-12 at 16:47 -0700, W. J. Karle wrote:
      > >
      > >
      > > Knowing that you are going with buried radials, I have a related
      > > question.
      > >
      > >
      > > It is difficult for me to determine, Dave, if the property is wide
      > and
      > > deep enough for a radial system of many (~32) quarter wave radials.
      > > Is it? If not, what radial strategy are you planning?
      > >
      > >
      > > 73,
      > >
      > >
      > > Bill
      > >
      > >
      > >
      > >
      > >
      > >
      > >
      > >
      >
      >
      >
      > ------------------------------------
      >
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      > 30 mtr digital Spots page made possible by Laurie VK3AMA
      >
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      >
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