CAL-AV Labs, Inc.

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Specifications 2D-20A


The 2D-20A is a 2-driven-element array for the 20 meter amateur band. It features full size elements, an internal phasing line, and an patented integral BALUN feed system. This beam has gain comparable to a 2-element Yagi, and a front-to-rear ratio comparable to a 3-element Yagi.

Physical Specifications

Wind Survival

The antenna is designed to reach the maximum allowable stress for the aluminum material at an actual airspeed across the elements in the worst case direction of 106 Miles Per Hour (MPH). We rate the elements to survive exposure to an airspeed of 100 MPH. This rating does not take ice loading into account.

With 1/2 inch of solid ice on the antenna, the wind survival speed is 47 MPH. With 1/2 inch of Rime ice loading, the wind survival speed is 50 MPH.


Elements: Aluminum, 6061-T6.

Accessories: Aluminum, Steel, PVC, Acrylic


Element Diameter: Elements taper from 1.5 inches to 0.375 inches

Element length: Front, 33.33 (32.6) feet; Rear, 35.75 (35.0) feet. First numbers are for lowest frequency of 13.85 MHz; numbers in parentheses are for mid-band.

Element sag: Front, 8.1 inches; Rear, 9.4 inches

Turn Radius: 18.3 feet

Projected area: 4.68 sq. ft.

Effective area (EIA RS222-C): 3.12 sq. ft.

Weight: 38.5 pounds, including mounting plates and hardware

Electrical Specifications

Rated Power: 1.5KW CCS, 3KW ICAS

Feedpoint Impedance: Adjustable to exactly 50 Ohms

The VSWR bandwidth will be approximately as follows when measured at the antenna terminals. Measurements made at the transceiver end of the feedline may show wider bandwidths than these.

190 kHz For 1.4:1 VSWR
420 kHz For 2.0:1 VSWR
595 kHz For 2.6:1 VSWR


Gain: 6.5 dBi minimum (free space), over the entire 20 Meter Amateur Band.

4.3 dBd (relative to full size dipole at same height) This number has been verified by actual measurement.

Front to back ratio: 20 dB

Takeoff angle: 26.4 degrees when mounted at the 35 foot minimum recommended height. See patterns and associated notes.

Vertical Beamwidth: 31.2 degrees; -3dB 12.4 and 43.6 degrees when mounted at the 35 foot minimum recommended height. See patterns and associated notes.

Horizontal Beamwidth: 73.4 degrees

Note: Please see patterns and graphs for more information.

Note: CAL-AV reserves the right to make and implement design improvements without notice.

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