Current Distribution Profile
This yagi has proven to be exceptional in use, best DX heard from the UK is VE1SMU/H beacon!
Richard Mason G6HKS builds this yagi, what a superb job! Richard is able to supply metalwork.
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!
NOTE: C=2.997925 X 108 meters/sec. Design Optimised at 144.300MHz
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| 'Netlon' mesh support clip on round boom. | VSWR, F/R etc performance graphs. |
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| E-Plane plot. | H-Plane plot. |
Back to Basics theme by Derek Hilleard G4CQM - Copyright © 2008 2009 All Rights Reserved
