Table of Contents

  1. Introduction
  2. Element Types
    1. Dipoles
    2. Wire Teeth
    3. Full-Wave Loops
    4. Bowties
  3. Controls and Readouts
    1. At a Glance
  4. Helpful Hints
    1. General
    2. How-To Videos
    3. NEC Analyzer How-To
  5. Example LPA Models
  6. Caveats
  7. Download

Log Periodic Calculator

Home:  ky8d.net/free 

Design a log-periodic array for any of ten different element types. Export your design for analysis in any of three formats: *.nec, *.ant or *.maa. Export it also to 3D CAD in the universally supported *.iges file format.

Introduction    ↑   → 

Front and center on the calculator's main tab is a scrollable array of all the more important measures useful in creating a common dipole array. Alternately, if designing a toothed array, start with the LHA (leading half-angle) tab next to that. Then on the File tab make a choice of nine different element types. Like so for a single-antenna build.

Or, better yet, output plural iterations of a design, then batch-analyze the whole lot to choose which might be best. How many elements are enough without overhsooting? Which design offers the lowest and flattest SWR? Which height and attitude affords the best gain? Set your computer to crank out a hundred or more slightly tweaked versions while you, yourself are AFK for the duration.

Analyze 100-plus files just as easily using the $39 NEC engine Nec2Go. All that's required is that 3rd-party program plus one of several free *.exe utilities which I wrote to support it. Learn about those on their own separate page:  HTTP 

Element Types     ←   ↑   ↓   → 

The example graphics below were generated by CAD from IGES files output by my calculator. After importing, I rounded off corners and fattened the wires up to pipe size, then took screenshots. Easier, that way, than trying my own hand at making actual art.

  1. Dipoles    ↑   → 

    graphic
    Dipole

    graphic
    Swept Dipole

    Above examples are both the same type, shown with differing angles of sweep. Only dipoles respond to non-zero angles of sweep.

    graphic
    Folded Dipole

    A necessary constraint imposed on folded dipoles is that, whatever you choose by way of inter-boom spacing, the fold-back wire will work out to an exactly equal spacing. Also for folded dipoles, closedly spaced parallel wires are divided into equal-length sections. This so that auto-segmentation for NEC will adhere to best practice.

  2. Wire Teeth     ←   ↑   → 

    graphic
    Trapezoidal Tooth

    graphic
    Sawtooth

    Wire tooth arrays will exhibit a slight frequency shift from the dipole-based calculation. Two, or possibly three iterations through an NEC analyzer may be required to exactly bracket desired ranges. Worth the effort, however. Very especially for sawteeth. Expect, however, for input Z to be of a high order.

    Note: saw teeth expresed as a wire outline are sometimes differentiated between 'cross-tooth' (as pictured above), and 'zigzag'. This latter is when the final element appears as a back-swept dipole (terminated at the apex, not returning back to the boom). You can have it either way. Ref:  XML 

  3. Full-Wave Loops     ←   ↑   → 

    graphic
    Quad

    graphic
    Quad Alt

    graphic
    Delta

    graphic
    Delta Alt

    Full-wave loops afford, on average, gain of 2dB over a dipole.

  4. Bowties     ←   ↑ 

    graphic
    Bowtie

    Bowties are tricky, their frequency being dependent on both the apex angle and side length. Separate controls for both of those can be found on the calculator's Alt tab. If bandwidth too wide, narrow the angle.

Controls and Readouts     ←   ↑   ↓   → 

My calculators all work like toys. Your creativity will not be channeled through a series of Y/N decision gates. It's a free-running loop, with every design parameter fully alive all the time. Work it by just playing around to see what results. Give that a few tries just only for starters.

Once you've got a feel for the concept, then proceed methodically. Employ the self-sequenced buttons for automatated hunting. Click once and sit back while boom-length, etc, auto-dial in their own adjustments.

Having got used to automated-hunt features, move on to the ultimate concept: multiple-file, automated design iteration.

  1. At a Glance    ↑ 

    Here are of the calculator's three main tabs, 50%-reduced. Click on any to see it full sized.

Helpful Hints     ←   ↑   ↓   → 

  1. General    ↑   → 

    Find a full description of all controls here:   List of Controls  

  2. How-To Videos     ←   ↑   → 

    These are very high resolution. Thus also very large files. Best to download first (rather than stream) if wanting to view on a smartphone. Because of that, though, you'll enjoy being able to read any text showing on my computer.

  3. NEC Analyzer How-To     ←   ↑ 

    You simply must have one or another of these, just on general principals. I have four: Nec2Go, EZNEC, 4NEC2, and MMANA-GAL. As regards use with this LPA calculator, I have a separate help page here:  XML 

Example LPA Models     ←   ↑   → 

 HTML  Link at left leads to where I'm collecting example LPAs. There you'll find graphs, models, everything.

Should you have a special need for an LPA not exampled, contact me via QRZ. If your need is interesting, I might model it for you gratis.

Caveats     ←   ↑   → 

Borrower beware! Yae, verilly. Though woe and lamentations betide you, know that already I’ve washed my hands. Sue me not. This is my standard End-User License Agreement. I wrote this utility solely and only for me. Nevertheless, you are welcome to share it for free. No promises whatsoever are made. There’s a bug in here somewhere of which I am blissfully unaware. There always is. That is in the very nature of freeware. It’s just how things are. Enough said.

Download     ←   ↑ 

You’ll need two things for it to run: my *.exe application itself, plus also the interpreter program on which it runs. Kind of like Java that way, except that the Java interpreter is probably pre-installed on your system. The LabVIEW run-time engine will not be.

  1.  LabVIEW Runtime Engine 
  2.  KY8D_Log_Periodic_Calculator.exe