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Cal-Av Labs 2D-40A User Manual

Dual-driven element 40 meter antenna
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USER MANUAL / ASSEMBLY INSTRUCTIONS
CAL-AV Labs, Inc. 2D-40A
DUAL-DRIVEN ELEMENT 40 METER ANTENNA
DESCRIPTION:
The 2D-40A is a rotatable horizontal array of two full-size, closely spaced driven
elements. Each element is about 70 feet long. The rear element is longer than the front.
They are fed approximately 140 degrees out of phase, using a shielded phasing line that
is inside the boom. The pattern is cardioid, with a free space forward gain of 6.5 dBi
and a front-to-rear ratio of 20dB.
Matching and fine tuning is by means of hairpin transmission lines mounted along the
underside of the boom near the feed point of each element. Both hairpins are adjustable.
The front hairpin is used to set minimum VSWR, which is specified as adjustable to 1.0:1
anywhere in the entire band. Adjustable element tip lengths set the intended operating
frequency of the array. It is noteworthy that all four element tips are moved by the same
amount for a frequency adjustment. The rear hairpin adjusts resonant frequency over a
small range, approximately 70 kHz.
Feed connection is by means of an SO-239 UHF receptacle located in the RF neutral
section of the forward hairpin. This patented feed, phasing, and matching system also
functions as a wide band, high power balun. Also, because the elements are electrically
connected to the boom at the neutral points of the hairpin sections, both a static drain
and a dc path for lightning-induced EMP or direct-strike current are provided.
In no-ice conditions, wind survival is 100 mph. With 1/2 inch of ice loading on the
elements, the wind survival is de-rated to 40 mph. Weight of the 2D-40A, including
hardware, mounting, and matching accessories, is 163 pounds (74.1 kg). For more
detailed information, including specifications, drawings, parts list, patterns and graphs,
please see the appendices.
UNPACKING:
The 2D-40A is shipped in three cartons; two are about 7 feet long, and the third is about
a 2-foot square.
Inspect cartons for any sign of shipping damage. Then open cartons and inspect the
contents for hidden damage. Shipping damage is not a common occurrence, but it does
happen. If damage is found, save the cartons and packing materials, and notify the
carrier.
Remove contents and inventory for the following:
Carton 1:
1 of each of the following: Front, rear, boom and mast mounting plates
1 kit Mounting plate hardware.
Revised 14 June 2003
1

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Summary of Contents for Cal-Av Labs 2D-40A

  • Page 1 UNPACKING: The 2D-40A is shipped in three cartons; two are about 7 feet long, and the third is about a 2-foot square. Inspect cartons for any sign of shipping damage. Then open cartons and inspect the contents for hidden damage.
  • Page 2 2ea. Coupling sleeves, boom, 3.25” diameter by 17.75” long. 1 kit Coupling sleeve hardware. 1 assy. Phasing line, dual RG-213/U, approximately 18.5’ long. 1 lot Rivets, closed end, three sizes in individual bags, incl. extras. 1 kit element hardware 1 kit Copper straps and hardware 4 ea.
  • Page 3 ASSEMBLY ELEMENTS This antenna has been sub-assembled at the factory and then disassembled for shipment. However, it is a good idea to check the measurements on the elements during assembly. The important measurements are those of the exposed lengths, that is, from the outer edge of an element component to the outer edge of the next larger one.
  • Page 4 Note: Tape is best removed by unwinding. This will result in a minimum of tape residue on antenna elements. Tape residue on elements can be removed with mineral spirits or WD-40. JOINING PIECES: Except for the feed point, which is joined to the fiberglass, assemble joints as follows: 1.
  • Page 5 Note: The feed-point and the next 2 joints out are fastened with 1/4"-20 stainless bolts. Be sure that the gray, slotted plastic insulator sleeves that go on the element to either side of the feed point are installed before joining the element halves.

  • Page 6: Boom Assembly

    Note: The most popular mast diameter is 2.0" O.D. The mast plate supplied as standard with the 2D-40A is for this size mast. If necessary, a mast plate for other mast sizes can be supplied, or the supplied plate can be drilled to accommodate the necessary size of U-bolt for the different size mast.
  • Page 7 ATTACHING THE BOOM TO ELEMENT MOUNTING PLATES It is now necessary to provide adequate support of nearly the entire length of the boom, because you will be adding significant and uneven weight to the boom in the next steps. This can be accomplished with a long table or 3 sawhorses (one for the center plate to control rotation).
  • Page 8 6. With one element mounting plate held level, using a small bullet level, check level on the other plate. 7. Twist one plate with respect to the other by grasping them and turning in opposite directions about the long axis of the boom. Now trial-tighten the twelve quarter-inch bolts, 4 in each of the two boom coupling sleeves, and 2 in each of the two element mounting plates, and recheck the level.
  • Page 9 Note: If the antenna is to be painted, now is the time to paint the boom. However, if you do paint the boom at this time be sure to take steps to mask the hairpin assemblies and connecting straps so that they do not get painted.

  • Page 10: Final Assembly

    FINAL ASSEMBLY ATTACHING AND CONNECTING THE ELEMENTS This procedure takes a space of 25 by 75 feet. This can be a driveway, rooftop, etc. Placing the boom on a couple of sturdy tables or sawhorses will make this assembly much easier. If absolutely necessary, it can also be done on a tower, with the boom vertical, and the plates and hairpins facing away from the tower.
  • Page 11 Settings for the exposed length of the element tips and for the position of the adjustable shorts on the tuning and matching should be made at this time. See APPENDIX E, “OPERATIONAL NOTES”, “Tune-up Procedures for the 2D-40A” to determine the proper dimensions to use for your intended mounting height.
  • Page 12 Note: Use an adequate number of people, patience, common sense, and great care. These will get your new antenna into the sky without damage to it or to you! If you are not experienced with installation of larger antennas, we strongly recommend that you get some very experienced help for the first few times.
  • Page 13 Appendix A Specifications for 2D-40A Description: The 2D-40A is a 2-driven-element array for the 40-meter amateur band. It features full size elements, an internal phasing line, and an innovative 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.
  • Page 14 We believe that this represents “average” ground conditions. The modeling program used for the electrical modeling is EZNEC V2.0 by Roy Lewellen, W7EL. Very accurate EZNEC models for the 2D-40A are available for download from the Cal-Av Labs, Inc. website <www.cal-av.com>.
  • Page 15 Figure 2-B 2D-40A Elevation Plot (antenna mounted 70 feet above earth) Figure 3-B 2D-40A Azimuth Plot (antenna mounted 70 feet above earth) Revised 14 June 2003...
  • Page 16 This curve is shown here only to give some idea of the relative difference in rate of rise in SWR for frequencies below system resonance as compared to frequencies above system resonance. Figure 4-B 2D-40A Modeled VSWR curve (antenna tuned for 7.1 MHz) Revised 14 June 2003...

  • Page 17: Mechanical Drawings

    50.5 (changes with tuning) Individual tubing dimensions are "exposed" lengths not including portion telescoped into next larger sized tubing. 2D-40A Front Element Overall Dimensions (element half length) 436.5 in (maximum boom center to element tip) (changes with tuning) 72 in...

  • Page 18: Parts List

    Appendix D PARTS LIST 1 assy. BOOM, consisting of: 1 assy. MOUNTING PLATE, BOOM-TO-MAST, CONSISTING OF: 1 ea. Mounting Plate, Mast, DWG. No. 020218-001-0001 4 assy. Clamp, 2", Stainless, ASSY/N MC9200SSA 1 ea. Mounting Plate, Boom, DWG. No. 020215-001-0001 4 assy. Clamp, 3", Stainless, ASSY/No. MC9300SS 4 ea.
  • Page 19 1 ea. Upper bushing piece, acrylic, DWG. No. 020221-001-0001 4 ea. Screw, 10-24 x 1", Phillips pan head 8 ea. Washer, flat, stainless, AN-960C10 4 ea. Nut, elastic stop, 10-24, stainless 1 ea. Block, Insulating, acrylic, DWG. No. 020221-003-0001 2 ea. Screw, 10-24 x 1" Stainless 2 ea.
  • Page 20 1 ea. Washer, Flat, AN-960C416 1 ea. Nut, Elastic Stop, 1/4"-20, Stainless 2 ea. Clamp, hose, all stainless, 71/95 mm, UPG P/N 4150 2 kit, STRAP, CONNECTING, HAIRPIN TO ELEMENT, consisting of: 2 ea. Strap, connecting, 0.625" wide, 8.5" long, DWG.
  • Page 21 6 ea. Washer, flat, AN-960C-416, stainless 2 ea. Washer, lock, split-ring, 1/4", stainless 2 ea. Nut, 1/4-20, stainless 2 ea. Tube Assy., 2.50" dia. 71.875" overall, all exposed, with 41" internal doubler, DWG. No. 020506-002-0001 2 ea. Tube, 2.25" dia., 0.125 wall, 58.75" overall, 52.0" exposed 2 ea.

  • Page 22: Operational Notes

    1. Physical spacing of the elements significantly less than 0.125 wavelengths for increased forward gain and, conveniently, a more compact boom. The actual spacing used in the N7CL arrays produced by Cal-Av Labs, Inc. is 0.11 wavelengths. So the array is more properly characterized as a “close-spaced” driven array.
  • Page 23 6. The design of the feed system rigidly enforces precise electrostatic balance for the array. Balance is maintained with regard both to the feedline connection and to the connection to the tower. This makes the antenna much quieter on receive and eliminates the need for a separate BALUN or coil of coax in the feedline to the transmitter.
  • Page 24 Tune-up Instructions for the Cal-Av Labs, Inc. Model 2D-40A Antenna This manual contains tabular data on the tuning and matching stub shorting strap positions and element lengths for an antenna mounted at the minimum recommended height of 1/2 wavelength above local earth and additional data for antennas mounted at one wavelength.
  • Page 25 Antenna Settings for 2D-40A Mounted at 70 feet (one half wavelength) Frequency Delta Tip Length (MHz) (inches) (inches) 6.962 50.5 7.030 45.5 7.099 40.5 7.170 35.5 7.241 30.5 7.313 25.5 Figure 2-E Tip Lengths vs Frequency (70 feet) If the antenna is to be installed at this recommended minimum height of approximately...
  • Page 26 (all four tips by the same amount) to bring the minimum SWR point to the desired frequency. The 2D-40A antenna will move about 14 kHz per inch of element tip length change. As you might expect, the resonant frequency of the array will rise with shortening element lengths.
  • Page 27 Antenna Settings for 2D-40A Mounted at 140 feet (one full wavelength) Frequency Delta Tip Length (MHz) (inches) (inches) 6.948 50.5 7.015 45.5 7.084 40.5 7.154 35.5 7.224 30.5 7.296 25.5 Fig 3-E Tip Lengths vs Frequency (140 Feet) If the antenna is to be installed at this height (approximately one wavelength), the sliding shorts used to adjust tuning and matching for the array should be preset as follows: The tuning (rear) shorting bar should be set to a distance of 25.3 inches back from the...

  • Page 28: Painting Instructions

    Appendix F PAINTING INSTRUCTIONS GENERAL: Should you paint your antenna? We think so, but it's your decision. Here are the facts: OPERATIONAL EFFECTS: Nil; a thin dielectric coating (paint) between the metal and the air does cause changes, but they would be very difficult to measure for antennas of this size. A slight reduction in precipitation static may be noticed.

  • Page 29: Surface Preparation

    has some very nice attributes. Among them are that it can easily be removed with acetone, even after it is dry, and that it is very easy to touch up, while wet, after it's dry, or days later. It will oxidize a bit after years in the sun; even then, it can be cleaned with an MEK-dampened rag, just enough to remove dirt and some of the oxidized paint, and then repainted.

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