A 5el 12.5 Ohm 50MHz Optimised Wideband Low impedance (OWL) Yagi
Premium commercial versions of this antenna at Innovantennas
The OWL by G0KSC provides the benefits of both OWA (Optimised wideband Array) 50 Ohm antennas with those of traditional low impedance antennas. More information on the OWL can be found in the CONSTRUCTION menu above
Do not look at the gain figure of this antenna and compare with other 6 element 50MHz Yagis. Compare the gain, F/B and bandwidth together against other antennas of a similar boom length. With 10.32dBi and a boom less than 4M long, this antenna will be a winner for field days and the rural Ham radio operator.
PLEASE NOTE:
- Special attention should be taken in ensuring the element spacing and sizes are absolutley correct upon a 12.5 Ohm Yagi
- If SWR is not perfect, D1 may also need to be adjusted. An analyser is reccomended for use when finalising 12.5 Ohm OWL Yagis
- Visit 'Making the OWL Match' for more information on the recommended matching methods
- Please add 2mm to each element to allow for insulator correction if using G0KSC insulators. Other insulators may require different correction, Email me for details
- A Folded dipole can be added in order to give this antenna a 50 Ohm feedpoint. I can calculate exact sizes for you if you mail me
G8FJG installed a folded dipole on his 12.5 Ohm OWL to give it a 50 Ohm direct feed, feedpoint.
PA0WRS combined his 5el 4m long OWL onto the boom of his SteppIR. See the bottom of this page for his comments
PA0WRS installed the G0KSC style Pawsey/Coaxial transformer. The additional wire ensures a fully symmetrical match
Performance UK/USA Version
Forward Gain: 10.32dBi at 50.250MHz
Front to Back Ratio: 21.26dBi at 50.250MHz
Peak Gain: 10.36dBi
Peak F/B: 21.90dB
Bandwidth: 500KHZ below 1.2:1
Build Dimensions for UK/USA Version
Element Spacing in metres Half element Length in metres Element Notes
Reflector 0 1.484 12.7mm 1/2 inch Diameter tube
DE .285 1.444 12.7mm 1/2 inch Tube
D1 .883 1.399 12.7mm 1/2 inch Diameter tube
D2 2.153 1.3535 12.7mm 1/2 inch Diameter tube
D3 3.995 1.275 12.7mm 1/2 inch Diameter tube
Build Dimensions for European Version
Element Spacing in metres Half element Length in metres Element Notes
Reflector 0 1.485 12mm Diameter tube
DE .285 1.444 12mm Diameter tube
D1 .891 1.400 12mm Diameter tube
D2 2.153 1.3545 12mm Diameter tube
D3 3.995 1.274 12mm Diameter tube
Fantastic Azimuth plot of this 5el 50MHz OWL Yagi
The Elevation plot is really clean too. A quiet antenna compared with most!
This SWR plot is taken with the Coaxial stub embedded within the EZNEC model Ever seen a 12.5 Ohm antenna like this one before? Watch how many now appear on the Internet but remember where you saw them first!
The G0KSC OWL element layout. Note the close spacing of the first 3 elements which give the OWL its extra gain and wide bandwidth.
PA0WRS had these comments on this 5el OWL build:
'Hello Justin
I like to report about a 5el 12.5 Ohm OWL yagi (according one of your models) I installed for test on the boom of my steppir beam last month.
As an ex-navy radio op I only had been qrv on HF since 1974 until I purchased a 3 el Steppir+additive director for 6m (from Ron-GW3YDX at Vine) in 2004. I did not have any 6m equipment at that time, but the Steppir went from 20 - 6 meters. In 2005 I bought a 2nd hand TS60 on 2dehands.nl (ebay equivalent in PA-land). Being an HF dxer I hoped to work some extra entities on 6m for my DXCC-Challenge. In 2008 I completed to work 100 dxcc's with this setup. I then replaced the TS60 with a FT2000d which has 50MHz on board. So I picked up a lot of entities with the steppir, but I got the feeling the F/B ratio could be better so the idea came up to add a dedicated 6m beam above the Steppir. Building this beam (6el) it became clear to me that the whole construction (Steppir + 6el beam) became to big, in the meantime since 2004 I already had extended the steppir with 30/40m trombone element, so .... Then I came to the idea to install a dedicated 5 el yagi on the boom of the steppir. In my mind when steppir elements were retracted this should work.
So after I worked the C56E dxpedition I installed the 5 elements on the Steppir boom, diameter of the elements is 10mm. Figures on YO are looking good, not much difference with 12mm diameter. I had tested it in the backyard at 2m high on a Fritzel boom I had in stock. I had some Fritzel insulators in stock and mounted junkbox covers on them on which the elements are fitted with heavy tiewraps. The idea is to work with this beam during the Es season only. The antenna is fed with 2x quarterwave pieces of RG-213 + Pawsey stub wire as described on ur site. Again when using the 50MHz yagi all steppir elements are retracted.
when I tested the 5 element in the backyard, SWR was perfect.
Now up in the air SWR of the beam is as follows (measured with my MFJ-259B):
MHZ SWR
49.3 1.4
49.4 1.1
49.5 1.0
49.6 1.0
49.7 1.0
49.8 1.1
49.9 1.2
50.0 1.3
50.1 1.3
50.2 1.3
50.3 1.3
50.4 1.2
50.5 1.2
50.5 1.2
50.6 1.2
50.7 1.3
this is not bad I think.
Though (of course) it is impossible to do a 1 to 1 comparison between the steppir en the G0KSC yagi I am sure the F/B ratio of the G0KSC is better. It is difficult to say something about the gain but I have had absolutely no problem with stations not hearing me.
Stations worked (outside a lot of EU station) include:
CU4/CU3EQ CU4/DL3GCS ZB2FK C37NL NN1N K1IM N1BUG VO1TA CU3/CT1FMX SV5BYR CR3L YO4RYU/MM EA8BLL EA8BMG TA2AD OH0/DK1MAX TF/DJ2VO LA/SM6CMU XT2EME (31 july - new DXCC!!). Pse note that unfortunately I missed some openings, especially to the Caribean/S-america.
I add a few pictures of both test and operational antenna. Note that the HF part of the beam points north and the 6m beam points south. This fitted best.
73 Wim PA0WRS'
