CUBEX SkyMaster Series

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Summary

Safety Warning

Fiberglass Material Precautions

Precautions for handling and processing fiberglass material, including recommended use of gloves and dust mask.

Preparation of Wire Elements

Wire Spooling and Management

Tips for managing wire spools and a convenient device for keeping wire manageable.

Element Winding Jig Method

A suggested method for winding accurate elements using a temporary winding jig.

Assembling the Support Structure

Boom Assembly

Details on coupling boom pieces and installing bridge truss eyebolts.

Element Spacing and Placement

Instructions for placing Reflector, Driven Element, and Director assemblies on the boom.

Assembly of the Boom to the Mast

Boom;Mast Coupler Installation

Placing and fastening the boom/mast coupler plate to the boom and mast.

Antenna Array Lifting and Securing

Lifting the antenna array onto the tower and securing the boom/mast coupler.

Driven Element Termination

Matching Stub Dimensions

Table detailing matching stub dimensions for various bands using RG11/U and RG8/U cable.

Arm Drilling Dimensions

Reflector Drilling

Specific drilling dimensions for the Reflector element arm for each band.

Driven Element Drilling

Specific drilling dimensions for the Driven Element arm for each band.

Director Drilling

Specific drilling dimensions for the Director element arm for each band.

Truss Arrangement

Element Spacing and Guying

Description of truss arrangement, element spacing, and supplied guying components.

Addendums

Joining Element Wires

Methods for connecting element wires using crimp sleeves or line men's splice.

6 Meter Arm Assembly

6 m Option Setup

Instructions for adding and securing spreader arms for the 6-meter band option.

The Cubex SkyMaster Series is a line of quad antennas, specifically the SKYMASTER III-3B and SKYMASTER III-5B models. These are 3-element quad antennas designed for 3 and 5 bands, with an additional capability for 6 meters. The manual provides comprehensive instructions for assembling, installing, and feeding these antennas.

Function Description:

The Cubex SkyMaster antennas are designed to provide efficient radio communication across multiple amateur radio bands. As quad antennas, they are known for their good gain, front-to-back ratio, and relatively low noise characteristics compared to some other antenna types. The 3-element design suggests a directional antenna with enhanced performance in a specific direction. The multi-band capability allows a single antenna system to operate on several frequency ranges, including 10m, 12m, 15m, 17m, 20m, and 40m, with an optional 6-meter capability. The antenna uses fiberglass spreader arms to support the wire elements, forming a square or diamond configuration.

Important Technical Specifications:

Antenna Type: 3-element Quad Antenna
Models: SKYMASTER III-3B, SKYMASTER III-5B
Bands: 3-band and 5-band configurations, with optional 6 meters. Specific bands mentioned include 10m, 12m, 15m, 17m, 20m, and 40m.
Spreader Arm Length: Approximately 13 feet (4m) when assembled, consisting of three telescoping fiberglass tubing pieces (Butt end: 48", Extension: 82", Tip: 48").
Boom Length: 18 ft (for 3-element Quad).
Element Spacing (3-element Quad): Reflector at one end, Driven Element at 10 ft mark, Director at the other end of the boom.
Feed-point Impedance: Varies by band: approximately 50 ohms for 20m, 75 ohms for 15m, and 110 ohms for 10m.
Matching Transformer: Cubex matching transformer (MT-3) is recommended for single feed line operation across multiple bands.
Coax Matching Sections (for remote switching/separate feed lines):
- 10 Meters: 68 inches (172.72 cm) of RG/11U 75 ohm coax.
- 12 Meters: 79 3/4 inches (202.74 cm) of RG/11U coax.
- 15 Meters: 92 inches (233.68 cm) of RG/11U coax.
- 17 Meters: No stub required, matches okay with 50 ohm cable.
- 20 Meters: Any length of RG 8/U 50 ohm coax.
- 40 Meters: 23.35 ft (420 in) of RG11/U coax.
- Velocity factor for 75 ohm coax: 0.66.
Element Wire Lengths (Total Length Cutting Chart - Table IIa):
- 10M: Reflector 39 ft, Driven El 38 ft, Director 1 35 ft
- 12M: Reflector 44 ft, Driven El 43 ft, Director 1 40 ft
- 15M: Reflector 50 ft, Driven El 48 ft, Director 1 47 ft
- 17M: Reflector 59 ft, Driven El 58 ft, Director 1 54 ft
- 20M: Reflector 80 ft, Driven El 74 ft, Director 1 70 ft
Element Wire Lengths (Per Side - Table IIb):
- 10M: Reflector 107.5", Driven El 105.0", Director 1 100.8"
- 12M: Reflector 124.0", Driven El 120.75", Director 1 117.25"
- 15M: Reflector 145.0", Driven El 142.0", Director 1 139.0"
- 17M: Reflector 170.5", Driven El 166.5", Director 1 161.5"
- 20M: Reflector 218.0", Driven El 212.0", Director 1 207.25"
Drilling Dimensions (from Butt End - Table III):
- Reflector: 10M (74-3/8"), 12M (85-1/2"), 15M (101-3/8"), 17M (118-1/2"), 20M (152-5/8")
- Driven Element: 10M (71-3/8"), 12M (83-1/2"), 15M (98-3/8"), 17M (115-1/4"), 20M (147-5/8")
- Director: 10M (69-1/8"), 12M (80-1/2"), 15M (96-3/8"), 17M (112-1/4"), 20M (144-7/8")

Usage Features:

Assembly Options: The manual supports two main design concepts for determining reflector and driven element lengths:
1. Making all elements physically equal and using stubs/inductors for electrical length adjustment.
2. Determining proper physical lengths (usually +/- 3%) before cutting.
Orientation: The square configuration is recommended over the diamond configuration, although physical dimensions can be used for either. The square configuration is believed to offer slightly higher forward gain.
Element Winding Jig: A temporary winding jig made from wood board stock (approx. 20 ft long) is suggested for accurate element winding. This helps form corners and minimize tangling.
Wire Pre-cutting: It is recommended NOT to precut the wire when using the winding fixture; instead, spool the entire wire around the "per side nails" and cut after forming the loops.
Element Identification: Elements should be clearly identified (e.g., 10 mtr. driven ele.) and corners marked for easy alignment.
Boom Assembly: The boom consists of two equal length pieces coupled with an insert section. Bridge Truss Eyebolts are installed for guying.
Mast Mounting: The boom/mast coupler plate is placed at the center of the boom (offset 6 inches toward the Reflector for improved clearance) and secured to the mast using U-bolts. Truss guying with Dacron rope and S-hooks is used for mechanical advantage and tensioning.
Feeding Methods:
- Cubex Matching Transformer: Recommended for single feed line operation with acceptable SWR across 3 or 5 bands.
- Remote Antenna Switch (e.g., AMERITRON RCS-8V): An alternative method using separate feed lines for each band, requiring Co-Ax matching sections from 75 ohm RG11U cable.
- Direct 50 Ohm Feed: Suggested to try first for 15 meters, as it may be satisfactory.
- Gamma Match: A solution for "rare" cases of difficulty with matching systems.
Element Connections: Reflector and Director elements are connected to complete the quad loop using crimp sleeves or a "linemen's" splice. Crimp sleeves allow for temporary positioning and tension adjustment before final crimping/soldering.
6 Meter Option: Requires adding two sets of spreader arms to pre-drilled holes in the boom for the Driven Element (RED) and the 1st Director (WHT). Secured with Phillips head screws and locking nuts.

Maintenance Features:

Safety Warning: Emphasizes the importance of reading instructions, wearing OSHA-approved safety harnesses, and hard hats for helpers during antenna work.
Fiberglass Handling: Precautions are advised when handling and processing fiberglass material, recommending gloves and a dust mask for cutting and drilling.
Wire Management: Wire is spooled in a large diameter to minimize curl and kinking. An inverted plastic water pail is suggested to keep wire manageable during un-spooling.
Tensioning: The crimp sleeve method for joining element wires allows for checking and adjusting wire tension before final commitment.
Boom/Mast Coupler: Bolts should be tightened sufficiently to prevent rotation, considering increased side loading with longer mast lengths.
Handling Precautions: Caution is advised when handling the assembly to prevent breakage from dropping or impacting against buildings or trees.
Matching Stub Adjustment: Some experimentation may be required to optimize impedance transformation with matching stubs.
Feed Line Pruning: Recommended as the primary approach for SWR adjustment when using the "Single Feed Line" (SF) method.
Excess Cable Management: Excess coax cable can be coiled into a 6-inch diameter coil and taped together.