G4CQM FREE YAGI BEAM ANTENNA DESIGNS FOR RADIO AMATEURS 6M 2M 70CM 23CM

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G4CQM 50-OHMS NATURAL IMPEDANCE YAGIS/BEAM ANTENNAS

RICHARD MASON G6HKS BUILDS AND TESTS 4 X 2M-1.0WL (6 ELE) YAGIS
Designed by G4CQM

7 FEB 2010 - 2 X 9 ELE G4CQM DESIGN YAGIS FOR SALE ON EBAY BARGAIN PRICE

G3TFR version of the 4X1UN 3 element yagi designed by G4CQM

Julian Hardstone G3TFR version of the 4X1UN 3 element yagi

6M 2M 70CM 23CM 50MHz 144MHz 432MHz 1296MHz

G4CQM FREE YAGI BEAM ANTENNA DESIGNS FOR RADIO AMATEURS 6M 2M 70CM 23CM

G6HKS G4CQM 432MHz 70cm 5WL Wavelength PowAbeam Antennas Kit

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Welcome to Derek Hilleard G4CQM's homebrew VHF/UHF/SHF Amateur (Ham) Radio yagi/beam antenna designs, published here freely for YOU to build for yourself.

I have been a professional antenna designer for more than 15 years, see me at www.antennadesigner.co.uk and you can find out more about me at QRZ.COM http://www.qrz.com/db/G4CQM.

G4CQM is now on Twitter, follow my tweets!

Antennas can be a very emotive subject, all said and done your Ham Radio station performance depends on it! So making the right choice should be top priority. I am old enough to remember the many WONDER ANTENNAS that have come and gone. In my view simple designs based on sound principles will stand the test of time and deliver consistent performance!

To help YOU construct your own antenna Richard Mason G6HKS and Derek Hilleard G4CQM are pleased to announce that we have joined forces to re-launch PowAbeam Antennas in kit form, the ultimate yagi kit! Despite the 'Credit Crunch' homebrew yagi construction is booming, increasing numbers of you are building your own yagis and we aim to encourage this. Remember this, if you are unable to hear them you will not work them. Build PowAbeam Antennas yagi kits and achieve both!

We would like to thank all the contributors to these pages who have themselves built the designs detailed here including VK3VG, 4X1UN, G3TFR, GW4DGU and M0ELS.

It is my opinion that 50-Ohm natural impedance yagis are the future and G4CQM's State-of-the-Art PowAbeam Antennas feature 'Direct Feed/Connect'! These yagi designs have been carefully optimised with YO7 PRO from Brian Beezley K6STI.

Background to PowAbeam Antennas and the designs

Back in December 1994 Derek Hilleard G4CQM began research for PowAbeam Antennas, inspired by 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 the yagi designs in both fixed station and portable applications. Read more...

PowAbeam Antennas and the 'Coaxial Dipole'

At the heart of my yagi designs is a 'Coaxial Dipole', it is in the same family as the Double Bazooka Dipole antenna (HAMUNIVERSE.COM ARTICLE).

Learn more about DIPOLES...(BBC R&D White Paper WHP 132 March 2006 Dipole antennas C. Gandy)

Wikipedia and Dipoles...

Learn more about the Yagi-Uda antenna...

My yagis have been designed to have a natural 50-Ohms impedance and so require NO MATCHING CIRCUIT. The 'Coaxial Dipole' is more than just a simple split dipole and eliminates the need for a balun. So there are NO MESSY COILS OF COAX, NO STUBS, NO UNPROTECTED CONNECTIONS AND NOTHING TO BURN OUT...IT ALSO OFFERS GREATER BANDWIDTH THAN FOLDED DIPOLES OR LOOPS...It is unrivalled in its simplicity and when used in a 50-Ohms direct feed yagi it will produce a highly efficient and low noise solution, ideal for weak signal communication!!

THE COAXIAL DIPOLE IS IN THE SAME FAMILY AS THE DOUBLE BAZOOKA ANTENNA

Graham Daubney F5VHX (F/G8MBI) has written an extremely informative article entitled "The design and feeding of Driven Elements for VHF/UHF Yagi Antennas".

JN53LK VHF CONTEST TEAM AND THE COAXIAL DIPOLE

The JN53LK VHF CONTEST TEAM inspired by my designs have also discovered the benefits of using a 'Coaxial Dipole' driven element! See their interpretation below and visit their website...

Ohmic Losses and a word of warning

At VHF frequencies RF currents travel along the surface of radiating elements and conductors (Skin Effect). It is for this reason that matching circuits and baluns can introduce additional Ohmic losses. By designing a yagi to have a natural 50-Ohm impedance and the use of a 'Coaxial Dipole', these losses can be significantly reduced. Keeping the radiating element as simple as possible and by using high quality materials and sound connections aids the transfer of energy.

Computer simulations must be regarded as a guide only and in some cases claimed gain figures and noise temperatures are not realised due to losses and inefficiency in the radiating element. There is no easy way to quantify the efficiency of a driven element other than like for like range testing on an antenna test range calibrated to traceable national standards. Merely looking at Return Loss or VSWR will not reveal an inefficent radiator, after all a dummy load presents a near perfect match! Designing a high performance yagi is one thing, building an effective and efficient yagi is quite another!

When you are choosing YOUR yagi, carefully consider the driven element, it is at the heart of the antenna and needs to be fit for the purpose!

Professional Driven Element Moulding to give YOU a head start

Professional Driven Element Moulding - Seen here in a commercial GSM 900MHz yagi

Professional Driven Element Moulding - O ring seals clearly visible

No messing about with PowAbeam Antennas, ALL kits come with a professional moulding to house the 'Coaxial Dipole'.

Finally, G4CQM discovered those Netlon clips
TWO SCREWS HOLD THE CLIP IN PLACE TO STOP ROTATION!

Netlon clips can be mounted on square or round section tubing - TWO SCREWS HOLD THE CLIP IN PLACE TO STOP ROTATION!

Ideal at 144/432/1296MHz

When I started PowAbeam Antennas back in 1994 I could not beleive my eyes when I found the Netlon clip. It was just what was needed to hold the parasitic elements in place and avoid the uncertainty in corrections required for other mountings. Frankly there is NOTHING else like them! FREE-SPACE dimensions can be taken straight to the boom. This has the distinct advantage that the yagis 'just work' provided YOU carefully follow the instructions. NO CORRECTIONS, NO COMPROMISE AND NO LOSS OF PERFORMANCE!

73's and successful DXing from Derek Hilleard G4CQM

QUESTIONS? CONTACT G4CQM - Email: g4cqm(at)live.co.uk

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P.S. Derek G4CQM and wife Diane are in the process of a huge clear out of unwanted items including radio gear, take a look at our Online-Car-Boot-Sale.

Finally, Henry Westlake of W.H. Westlake Electronics now has in stock a very large quantity of brand new LDF450A (in copper) very low loss coaxial cable at a bargain price! If you want to upgrade your feeder then don't miss this opportunity!