ARLA/CLUSTER: Sistema de alimentação revolucionário para antenas Yagi.
João Gonçalves Costa
Segunda-Feira, 23 de Março de 2009 - 11:37:23 WET
Revolutionary Yagi Antenna Feed System
Justin Johnson G0KSC, says that he has pioneered a revolutionary new feed system for the Yagi directional beam antenna, which will see it's Debut in the next issue of DUBUS - the serious magazine for VHF and up amateur radio www.dubus.org<http://www.dubus.org/>.
Whilst there are many benefits seen with the new system, the most important break-through is the suppression of the age old problem of unwanted side lobes within longer Yagi designs.
The feed system (which does not consist of a dipole and no, it is not a Quagi!) has 2 different feed points. Whilst the antenna needs re-modeling in order to change from one to the other, different characteristics are seen from each method. The first enhances the bandwidth capabilities of the Yagi and presents never-seen-before ultra low return loss, excellent gain and front to back ratio, whilst the other provides more traditional OWA (Optimised Wide-band array) style bandwidth with good improvements in forward gain and massive improvements in front to back ratio.
What people say
'This could be a turning point in the development of the Yagi Antenna'
Popa, YU7EF - World renowned Yagi antenna designer/engineer - www.yu7ef.com<http://www.yu7ef.com/>
'Justin, Indeed this looks like a unique and winning design!' Joel R. Hallas, W1ZR - Technical Editor, QST Magazine
'Hi Justin, Many thanks for the plots, these diagrams look really beautiful! I have never seen such F/B and low sidelobes for a Yagi before'
Joe CT1HZE - DUBUS Magazine
Benefits of the new design
Whilst going to press, experiments are still being conducted with the new Yagi. However, the new feed adds a number of very interesting characteristics to the Yagi which when focus is applied to optimisation, excellent not-seen-before Yagi performance is the result. The list so far consists of the following:
* Superior Front to Back Ratio with very high suppression of unwanted lobes
* Extended/alteration of 'ideal' boom length
* Exceptional clean pattern performance
* Ultra-wideband characteristics
* 50 Ohm impedance - no matching required
* Easy fine-tuning of feed arrangement itself
More information and plots at: http://www.g0ksc.co.uk/latest-design.html
a 10el 144Mhz high gain, low loss Yagi with the new feed system
50 Ohm impedance, no matching unit required
As with all of my designs which keep the amateur antenna builder, novice or professional in mind, no matching unit, coaxial stubs or any other tuning arrangement needs to be added to the antenna. A simple 1:1 balun or coaxial choke balun at the feed point is enough. As stated above, direct feed of the antenna is possible and due to the design of the feed system itself, fine tuning can be achieved easily. Full details in DUBUS! www.dubus.org
Some plots of Yagis created so far:
A 9el 50Mhz G0KSC Yagi - How clean is that pattern!
Even the elevation pattern is looking good
Ultra low return loss to go with the flat SWR
Fantastic front to back not seen with no unwanted forward lobes before
Nice near 50 Ohm impedance too
A preview of the 11el 144Mhz Yagi to be featured in DUBUS below:
8el on 50Mhz with very high F/B and no lobes
10el for 144Mhz, a nice clean pattern
Ever seen a pattern like this from a 5el 50Mhz Yagi?
The 5el Yagi for 50Mhz looks good elivation wise too
Visit www.DUBUS.org for details of the next issue release date.
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