We decided to change the 5 el LFA into a 6el OWA in order to gain more band width. The LFA was a strong performing antenna but it just didn’t have the band width that the design, also from Henry at HPSD Antenna Systems in Holland. http://www.hpsd.nl/ Henry knew we had an 8 m boom and had to design around that. The design Henry provided only used 7.22 m of that 8m. Although the beam has 4 directors the first director is placed close to the driven element to bring the impedance up to 50 ohms for direct feed with coax via a 1:1 balun. Takes the matching system out of the equation and allows direct coax to element connection which I prefer. The Driven and all elements are insulated from the boom.
This is what Henry has to say about the OWA design…
The OWA yagi (optimium wideband antenna) is a antenna wich has its origin from Jim Breakall, (WA3FET) .
With a OWA you actually achieve over wide frequency high gain and high front to back figure while remaining a 50 ohm impedance. (and not only in the “SSB DX” section of the band)
They are know to be used by many ,and as mentioned..not for nothing. They are overall winners for all possible “antenna” jobs.
Direct 50 ohms impedance.
Wide band SWR (example 28-30 Mhz or 27-29 Mhz)
Extreme low return loss
HIGH power handeling
Non critical for wheater influence
With only a couple extra parts the OWA can be changed into a F-yagi if needed. If you are looking for a solid workhorse for a wide frequency range the OWA is the way to go.
6el owa 91dd018 (2) The PDF file from eznec for those who are interested.
Open the PDF file above to see the antenna modelled with Eznec. Shows a swr under 1.5 for almost 3mhz from 26mhz through 29mhz with a 10dbi gain throughout. F/B is 20db with a bit less around 27.5. Looks almost too good to be true.
I measured up all the elements making sure they were centered on the boom to the nearest mm. Went over them all 3 or four times to check. The balun is a 5kw “Balun Designs” 1:1 Balun. Good stuff! Up she went and off she goes.
The SWR graph obtains is the same as the one in the model so I have to assume the rest of the predictions will hold true as well. I have not had much chance to test it yet as the rotator is still being serviced but hope to give it a good run to Europe shortly. It certainly hears very well and surprisingly the SWR changes only slightly when we raise power from 50w to 1kw. Like from 1.3 to 1.35. I am rather ecstatic to say the least. I recommend Henry and his programs to design and make yagi’s!
If I could change anything I may shorten the Driven element a little to drive the curve further up into the FM portion of 10m. I think the 6″ leads from the Balun to the Driven element have possibly caused the point of low SWR to be around 26.8mhz rather than 27.5mhz. The good thing about an antenna such as this is that it doesn’t really matter!!! Plenty of band width regardless.
When I ordered this antenna from Henry about 18 months ago we discussed ways to send the beam to Indonesia cheaply from Holland. In order to keep the length down under the postal regulations of 4 ft or so Henry decided to split the elements in the middle and provide joiners, and we would source the boom material locally. Brilliant. After bouncing around at sea for a couple of months a tube arrived filled with 2 sizes of very thick walled Aluminium and all the fittings. It all fitted perfectly. To convert the LFA to an OWA I had to cut up the loop and use the small end loop pieces to extend the driven element and the 3rd director.
Go HPSD Antenna Systems!!