Enhanced OWA

Some years ago Jim Breakall, WA3FET, devised the Optimized Wideband Array. It is a Yagi with close-spaced first director that provides low SWR over a wide bandwidth with direct 50Ω feed. Although the OWA has less forward gain than a conventional design with matching network, its wide SWR bandwidth and feed simplicity make it popular.

Bending the OWA driven element can improve forward gain while retaining wide SWR bandwidth and direct feed.

Modeling Results

I used AO 9.66 to maximize forward gain for a 4-element OWA on a 570″ boom with F/R no less than 22 dB and SWR no greater than 1.4 over 7.0 to 7.3 MHz. The blue curves show the response. Then I let the driven element bend in the center and reoptimized with the same constraints. The red curves are for a 7.2 bend. Bending additional elements can provide up to 0.3 dB more gain.

Gain/Pattern Trade-Off

To explore the gain/pattern trade-off, I reoptimized with maximum SWR of 1.4 and varied minimum F/R.

Gain/SWR Trade-Off

To explore the gain/SWR trade-off, I reoptimized with minimum F/R of 22 dB and varied maximum SWR.

Narrowband Pattern

Some OWAs are designed for a good pattern at the low end of the band but allow it to degrade higher up where it may not be needed. Relaxing F/R bandwidth yields much higher forward gain. A bent driven element offers less advantage for these designs. The dashed curves below are for OWAs with narrowband F/R. The solid curves, from above, are for wideband F/R.

The green curves are for a 3-element Yagi with bent driven element and hairpin match. I think most amplifiers should handle the SWR to at least 7.25 MHz. This design has intermediate gain and a decent pattern over the lower half of the band. It offers lower material cost and wind load than the 4-element designs.

Antenna Files

Enhanced OWA
Free Space Symmetric
7 7.075 7.15 7.225 7.3 MHz
4 6061-T6 wires, inches
ang = -7.20994
x1 = 0
x2 = 138.63
x3 = 245.5951
x4 = 570
y1 = 413.1038
y2 = 404.9571
y3 = 386.8065
y4 = 365.7719
1  x1 0 0  x1 y1 0  1.4
rotate end1 z ang
1  x2 0 0  x2 y2 0  1.4
rotate end
1  x3 0 0  x3 y3 0  1.4
1  x4 0 0  x4 y4 0  1.4
1 source
Wire 2, end1


Enhanced OWA - Narrowband F/R
Free Space Symmetric
7 7.1 7.3 MHz
4 6061-T6 wires, inches
ang = -8.210171
x1 = 0
x2 = 156.1316
x3 = 275.1442
x4 = 570
y1 = 412.7051
y2 = 403.4081
y3 = 386.9267
y4 = 371.5446
1  x1 0 0  x1 y1 0  1.4
rotate end1 z ang
1  x2 0 0  x2 y2 0  1.4
rotate end
1  x3 0 0  x3 y3 0  1.4
1  x4 0 0  x4 y4 0  1.4
1 source
Wire 2, end1


3-Element Yagi with Hairpin
Free Space Symmetric
7 7.05 7.3 MHz
3 6061-T6 wires, inches
ang = -12.6433
x1 = 0
x2 = 275.3429
x3 = 570
y1 = 411.1258
y2 = 400.6867
y3 = 365.677
1  x1 0 0  x1 y1 0  1.4
rotate z end1 ang
1  x2 0 0  x2 y2 0  1.4
rotate end
1  x3 0 0  x3 y3 0  1.4
1 source
l1 = 209.726
Wire 2, end1 l1 pF

July 17, 201888108 MHz