On Friday 2nd December LEFARS were pleased to receive Justin Johnson G0KSC and Joe (József) Gyöngyösi HA5CW / M0HAA from InnovAntennas, Canvey. This visit was scheduled last month but had to be delayed. Justin is well known for his innovative Yagi designs and he was happy to share his knowledge and experience.
The meeting started with Justin providing an overview of his Yagi designs and computer design technology using programs costing 4-figure prices. Impressive images of G0KSC HF Yagis and arrays built to his OWA (Optimised Wideband Array) design by amateurs worldwide were shown. The design information is freely available to make your own Yagi. The OWA design provides maximum performance whilst maintaining a 50 Ohm impedance in order to help ensure minimum losses and maximum radiating efficiency. With low and flat SWR curves, return losses are minimised. The OWA design does not require any matching system (ATU/AMU etc.) and provides excellent stability even in rain; it will not de-tune.
For more information, including build instructions, visit Justin’s website (links below). Design data is provided for HF (20m-10m),6m and 2m OWA Yagis. These range in sizes ranging from 4 to 7 elements for HF, 4 to 11 elements for 6m, 8 to 16 elements for 2m.
Justin G0KSC went on to describe the development of the LFA and OWL range of Yagi antennas. The Loop Fed Array Yagi (more LFA info here) replaces the traditional split dipole element with a rectangular loop; this provides a 50 ohm feedpoint impedance and no matching. The OWL (Optimised Wideband Low Impedance) Yagi build on the characteristics of the OWA Yagi and utilises the low impedance characteristics (wide bandwidth and good front to back ratio) whilst improving side lobe suppression; important to reduce the effect on one’s neighbours and possible QRM (plasma TVs etc.). More info on OWL antennas and design here. Justin also covered other important aspects of Yagi design and construction. For high frequency antennas, build accuracy is paramount. CNC equipment is used by InnovAntennas in their new factory at Canvey to manufacture parts to better than 0.1mm. The budding home builders were re-assured that this is not so critical for HF and VHF antennas. Using SWR and frequency plots, Justin also showed the importance of achieving a low-noise design and maintaining a low SWR across the entire bandwidth.
After Justin’s talk, there was plenty of time for the members to ask questions. For those who want to build their own Yagi, Justin sells the a range of insulators, clips, boom and element end clips etc. Also fully assembled antennas to his various patented designs. InnoVAntennas moved to their new factory in Canvey last month (November 2011).
We wish to thank Justin G0KSC and Joe HA5CW / M0HAA of InnovAntennas for taking time to visit LEFARS.
LEFARS Newsletter Editor.