- G4CQM Homebrew/DIY Antenna Specialist -
VHF/UHF/SHF HAM (AMATEUR) RADIO YAGI AERIAL DESIGNS

2M-2.5XX (144MHz) 2.5WL (WAVELENGTH) YAGI

Current Distribution Profile

2M-2.5XX YAGI HOMEBREW BY G4CQM

This yagi has proven to be exceptional in use, best DX heard from the UK is VE1SMU/H beacon!

G6HKS BUILDS THE 2M-2.5XX

Wow! Richard Mason G6HKS builds this yagi, what a superb job!

Richard Mason G6HKS builds this yagi, what a superb job! Richard is able to supply metalwork.

CONSTRUCTION

BREAKING NEWS 06/07/2006...

What an evening! Just worked UX1DK 59 in KN18DP to the East followed by CU8AO 59+ in HM49KL QRB 2420.64KM to the West using this Yagi!

The 2M-2.5XX Yagi was designed by me using YO7 PRO. It features 50 Ohms 'Direct Feed' for maximum efficiency. The driven element can be as simple as a split dipole with decoupling sleeve or ferrite on the feeder. Alternatively, a coaxial dipole that I devised, employing an ABS/Polycarbonate enclosure from RS and 'N' Socket. It can look very professional if you think out carefully the final construction. To obtain best possible results without ANY compromise, I used 'Netlon' mesh support clips available from many garden centres! They give electrically boomless performance providing sufficient stand off from the metal boom. You can use round or square alloy, I prefer round. Suitable Alloy 6082T6 Seamless Drawn Tube (used in Hang Gliders and Microlights) can be obtained in round sizes of 1" (17swg), 1 1/8" (17swg) and 1 1/4" (17swg). With a wall thickness of 1.42mm this tubing makes up a TAPERED BOOM with very good slide in fit properties and low wind profile.

Below are the dimensions based on 3/16 Inch OD (4.76mm) rod parasitic elements. To drill the boom accurately, make up a jig using engineering 'V' blocks. I purchased a second hand pair at Barnstaple market for a few pounds sterling. Driven element tube can be ideally 3/8 or up to 5/8 Inch OD.

This antenna will give you outstanding results if constructed correctly. I have worked EA8 with 500mW many times and heard VE1SMU/H the TransAtlantic beacon in Halifax with this Yagi! Stacking info can be found on my Interactive Page (CLICK). The 'Netlon' clips will require their spine to be enlarged by drilling out to M4 size. Then secure with studding cut to length and a size 8 self taper located in the remaining hole to stop rotation. Use M4 hardware to secure boom sections and remember shakeproof washers! It is advisable to use ALL STAINLESS STEEL hardware. An 'Eight Nut' clamp is OK to hold boom to stub mast, I used an old J Beam clamp. When drilling the boom I made up a little aid/jig based on a miniature spirit level mounted on an alloy angle bracket with M4 screw. This enabled the correct alignment of each element mounting hole to be maintained down the length of the boom for that professional finish!