All featured designs require 1 Inch (25.4mm) square section aluminium...
Parasitic elements and DE require 1/2 Inch (12.7mm) diameter tube.
Lay out boom, mark position of reflector element, measure all other element positions from this point.
Aim for the nearest mm!
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 pass band.
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 web browser! Double 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 length
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
Do not use plastic end caps on the parasitic elements (reflector and directors), these will affect tuning!
The DE length is end to end which includes the centre gap!
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!
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!
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.