- G4CQM Homebrew/DIY Antenna Specialist -
VHF/UHF/SHF HAM (AMATEUR) RADIO YAGI AERIAL DESIGNS
YAGI HOMEBREW/DIY PARTS NETLON CLIPS DRIVEN ELEMENT MOULDINGS
Richard Mason G6HKS combines my 9ele 2m and 70cm 14ele designs on one boom, excellent job!
Homebrew/DIY Parts
|  | |
|  |
INTRODUCTION - PLEASE READ BELOW!
Most of the 'Direct Feed' Yagi designs detailed in the pages of this website were originally intended as State-of-the-Art commercial designs for PowAbeam Antennas. They are as a result of a more than six year long research project started in late 1994 and ending in 2001. Countless thousands of hours were spent in the optimisation process and subsequent rigorous testing.
Inspiration came from the legendary work of Guenter Hoch DL6WU and Rainer DJ9BV. Thanks to top DX'ers Joe Ludlow GW3ZTH and the late Norman Vincent G3NVO who provided invaluable support testing my designs in both fixed station and portable applications.
The design concept is focused on the 'Current Distribution Profile' ensuring that ALL of the Yagis elements are active. Thus the 'Optimised Current Vector Yagi' was born, a phrase quoted in the original advertising literature describing the unique nature of these antennas.
The designs are published here to encourage fellow Radio Hams to experiment and 'have a go' at building their own antennas!
Shalom Cohen 4X1UN (KM72JB) constructed my three element 2M 'Direct Feed' Yagi and had a record breaking E's contact on June 6th 2007 at 16:24 UTC working CT1HZE (IM57NH). A staggering distance (QRB) of 4008.06KM (2,490.49 miles), a feat normally only attributed to the Big Guns! Well done to Shalom!
E-mail received from Richard Mason G6HKS
Derek, Also just for your info I worked RA6AX on Monday night on EME with 40 watts into the 9 ele CQM, he was -6 (S1 on the meter) which is strong and got -24 by return (full power we may have been able to make it on SSB)? Good condx but this really vindicates your excellent design and the direct drive element is great. Like you I cant believe people still go for baluns etc to match their elements and take the .2db loss !!!
73's Richard G6HKS
FEEDER CABLES
Ignore this at your peril! Use the best quality cable and connectors you can afford. Keep your feeder cable run as short and direct as possible. Finally, minimise the number of external connections, making sure they are completely weather-proof! I have just upgraded to ECO15 flexible low-loss coaxial cable.
Element Rod, Tubing Sizes and UK Suppliers
In the UK we are still using imperial sizes. All of my designs except the 4X1UN three element are constructed with tubing purchased locally from Blackburns formerly Baco Metal Centres (CLICK).
Alternative suppliers here in the UK are Forward Metals Ltd (CLICK) and George King Metals - 224 Tooting High Street, Tooting
London, SW17 0SG - Tele: 020 8672 8538.
The 'Netlon' clips used from 144MHz upwards hold 3/16 Inch OD rod (4.76mm) but will take 5mm sold in Europe. However, the Driven Element Moulding was designed specifically for 5/8 Inch OD tubing (15.88mm) and it is not advisable to use 15 or 16mm OD supplied in the EU.
My 50MHz designs use 5/8 Inch OD tubing (15.88mm) for the Driven and Parasitic Elements, you will need to fabricate insulated above the boom supports.
Richard Mason G6HKS - Metal Work Supply
Richard Mason G6HKS has offered, "should you be contacted by people who need any of the metal requirements I will be happy to oblige with element kits (+ square booms if people can collect)". Richard can be contacted by e-mail at richard.mason3@sky.com
USING NETLON CLIPS
The 'Netlon' clips will
require their spine to be enlarged by drilling out to M4 size.
Then secure with Stainless Steel studding cut to length and a Stainless Steel size 8 self taper
located in the remaining hole (under the element) to stop rotation.
Use Stainless Steel shakeproof washers and nuts to hold the studding.
Regard the spine of the clip as the rear. Note that the element is then offset forward by 8mm. You will need to allow for this in determining the absolute positions of ALL the Yagis elements.
BOOMS
144MHz Yagis that are longer than my 2.5 Wavelength design will require an overhead support wire.
This also applies to the 6M 1 Wavelength antenna.
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.
IMPERIAL - METRIC CONVERSIONS
| Inch | mm |
| 3/16 | 4.76 |
| 3/8 | 9.53 |
| 5/8 | 15.88 |
| 7/8 | 22.23 |
| 1 | 25.4 |
| 1 1/8 | 28.58 |
| 1 1/4 | 31.75 |
| 1 3/8 | 34.93 |
DIRECT FEED/CONNECT YAGIS
Why 'Direct Feed' Yagis? and important construction tips
With the arrival of modern computer software in particular YO, it has been possible to accurately design a Yagi with a natural 50-Ohm feed impedance. A Yagi is an ideal antenna for impedance manipulation because it has several parasitic elements that interact with the driven, determining feed impedance etc. This occurs as a result of their length, diameter and spacing distances. YO can instantly display the Yagi's characteristics such as F/B, Forward Gain, Polar Pattern and Impedance as a result of the antennas dimension changes.
Frankly I am amazed that people still persist in using folded dipoles, gamma matches etc etc. There is now no need for these narrow bandwidth, cumbersome and lossy matching devices! Infact most commercial designs originate from the dark ages when it was all done by trial and error and rule of thumb such as 5% shorter for the first director element etc.
A 'Direct Feed' Yagi can use a simple split dipole with the coaxial cable terminating directly onto it. A suitable ferrite can be placed over the coaxial at the feed point to reduce radiation from the screen and improve imbalance. Suitable alternatives include the use of a decoupling sleeve or a 'Coaxial Dipole'. If using a tail and connector always cut its length to 1/2 wavelength x cable Vf or multiples thereof. This will prevent impedance transformation and resultant mismatch!
The Yagi still offers Amateur Radio operators one of the simplest and most effective antennas for working long distances. A 'Direct Feed' Yagi offers the ultimate in performance. My sincere thanks goes to K6STI for his YO7 software which was years ahead of its time. This was because of the range of advanced features it offers to the Antenna Designer and the ability to see the result of changes instantly. The YO7 Professional version that I use is calibrated to NEC and one can toggle between both to scrutinise results.
As a Professional Antenna Designer (www.antennadesigner.co.uk) I have had the opportunity to verify on a test range calibrated to traceable National Standards the YO predictions regarding pattern and gain, it has proven to be remarkably accurate! And in my opinion there is still nothing as powerful as YO for Yagi design!
If you decide to construct Yagi designs from my web pages they must be accurately replicated, including the number of elements and dimensions. However, a good Yagi design is more tolerant of error than a bad design (allowance for tubing OD and element spacing tolerances), DO NOT change the number of elements.
Finally, please note that ALL element lengths detailed on my web pages are FREE-SPACE dimensions i.e. electrically boomless construction. From 144MHz upward 'Netlon Clips' are ideal supports therefore, raising each parasitic element by more than one-half the boom radius above the boom.
73's Derek Hilleard G4CQM
UNDER CONSTRUCTION!
John Randall MOELS constructs two of my 10 Wavelength 1296MHz Yagis on square boom
PAYMENT AND DELIVERY
Overseas orders now accepted. Credit and Debit card payments taken. Send money with PayPal or PPPay.com by E-mail. UK amateurs can pay me with their personal cheques.
1. Quick reference United Kingdom delivery charges (CLICK)
2. Post Office UK and Overseas Mail delivery charges (CLICK)
'Netlon Clips' shipping weight - ALLOW 6gm EACH (MIN QUANTITY 10). Driven Element Moulding shipping weight - ALLOW 81gm EACH. In addition add GBP 2.00 for packing materials.
Contact G4CQM
SITE NAVIGATION MENU
6M (50MHz) YAGIS
2. 6M (50MHz) 1WL VK3VG 6ELE YAGI
2M (144MHz) YAGIS
3. 4X1UN - SIMPLE 3 ELEMENT 2M (144MHz) YAGI
4. 2M (144MHz) 1WL G6HKS 6ELE YAGI
5. 2M (144MHz) 2.5WL 9ELE YAGI
6. 2M (144MHz) 3.4WL 11ELE YAGI
7. 2M (144MHz) 4.6WL 16ELE YAGI
70CM/23CM (432MHz/1296MHz) YAGIS
8. 70CM (432MHz) 5WL 14ELE YAGI
9. 23CM (1296MHz) 10WL 26ELE YAGI
CALCULATORS - STACKING YAGIS/CABLE LOSSES
10. Stacking Yagis etc
11. Coax Cable Losses
YAGI PARTS
Back to Basics theme by Derek Hilleard G4CQM - Copyright © 2008 2009 All Rights Reserved
