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.
Lay out boom, mark position of reflector element, measure all other element positions from this point.
Aim for the nearest mm!
- 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
- 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!
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!
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!