Construction...

Please read carefully the following notes...
If you haven't built your own yagi before, construction guidance offered here will hopefully stop you making mistakes that will prevent your build from working as it should! G4CQM's Antennas designs do not require any adjustment!...

 

  • Boom size

    All featured designs require 1 Inch (25.4mm) square section aluminium. Use heavy wall gauge for the longest booms...
  • Element size

    Parasitic elements and DE require 1/2 Inch (12.7mm) diameter tube.
  • Measuring

    Lay out boom, mark position of reflector element, measure all other element positions from this point.

    Aim for the nearest mm!
  • Tolerances

    Measure and cut the parasitic elements to the nearest mm. However, it is better to cut them 1mm too short than 1mm too long. Reason: Yagis have a frequency response similar to a Low Pass Filter so it is very important to keep the cut off frequency out of and above the desired pass band.
  • Element Mounting

    ALL DIMENSIONS ARE FREE-SPACE

    ELEMENTS NEED TO BE INSULATED FROM AND RAISED SUFFICIENTLY HIGH ABOVE THE BOOM TO AVOID BOOM CORRECTION AS PER DL6WU MOUNTING DIRECTIVE! I.E. RAISED MORE THAN THE BOOM RADIUS (r) ABOVE THE BOOM...

    No boom correction is required if you follow this advice!
  • Element lengths and positions

    Look for the .nec files, these are simple text files and can be opened/viewed with your text editor or even web browser!
    Double (x2) the element lengths shown in the file to calculate actual end to end length! See example below...
Key to symbols.nec example file

PADIA = Parasitic element diameter
DEDIA = Driven element diameter
RP, DEP, D1P etc = Element position
R, DE, D1 etc = Element 1/2 length

Look for the .nec files, these are simple text files and can be opened/viewed with your web browser!

  • Boom Correction

    USING PROFESSIONAL ELEMENT CLIPS FROM RW BADLAND LTD BOOM CORRECTION IS REQUIRED AS FOLLOWS: ADD TO THE TOTAL LENGTH (END TO END) OF EACH PARASITIC ELEMENT (NOT DE)...

    50 & 70MHz = 0mm
    144MHz = +6mm
    432MHz = +7mm
  • End Caps...

    Do not use plastic, vinyl, or rubber end caps on any of the elements (reflector, driven and directors), these will affect tuning and make wet weather performance worse!
  • Driven Element

    The DE length is end to end which includes the centre gap!
  • Boom length

    Allow an additional +50mm at either end of the boom to maintain tuning across its entire length, and also give a professional look...
    Example: WA6XX Reflector to D4 spacing is 2400mm + 50mm + 50mm = 2500mm BOOM LENGTH!
  • VSWR

    It is unlikely that reflected power will be exactly 1:1 in the operational bandwidth, a small amount of reflected power is normal due to software limitations and construction tolerances... Don't tune with your test equipment, use as a guide/reference only!
  • WARNINGS

    DOUBLE CHECK YOUR MEASUREMENTS BEFORE YOU CUT & DRILL!

    DO NOT ALTER THE DESIGN IN ANY WAY I.E. NUMBER OF ELEMENTS, LENGTHS, DIAMETERS OR POSITIONS. IF BUILT CORRECTLY THESE DESIGNS WILL NOT REQUIRE ANY ADJUSTMENT!

G4CQM's Antennas...

  • THESE YAGI ANTENNA DESIGNS ARE NOT FOR COMMERCIAL USE OF ANY KIND WITHOUT PRIOR CONSENT!
  • Private experimenters are free to use these designs for their own personal enlightenment. However, no guarantee or warranty is offered or implied.
  • MY WEBSITE DOES NOT USE COOKIES, EXTERNAL LINKS MIGHT!
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