Building Yagis – Part 3 (SteppIR DB36)

SteppIR DB36 Yagi

SteppIR DB36 Yagi (Courtesy SteppIR)

We have begun the assembly of the first of our two SteppIR DB36 Yagis. These antennas are large, complex machines that take some time to assembly properly and I plan to cover this part of our project in multiple posts. I will provide more pictures and details on this part of our project in hopes of helping others who might be building one of the SteppIR Dream Beam (DB) antennas. The DB36 covers all Amateur bands from 40m – 6m by using adjustable length elements which are controlled by Stepper motors. Each antenna includes a controller which sits in the shack and monitors the transceiver connected to it and continuously adjusts the elements for optimum performance as the transceiver is tuned. The following are the specifications for the SteppIR DB36 (Courtesy SteppIR): 

Specification DB36 DB36 with 80m
Dipole Option
Boom Length 36 ft / 10.97 m No change
Boom 1.75 – 2.5 in
4.45 – 6.35 cm
No change
Longest Element 49 ft / 14.9 m No change
Turning Radius 26 ft / 8.0 m No change
Weight 160 lb / 72.8 kg 164 lb / 74.39 kg
Available saddles for mast
(2.0 in / 5.08 cm is standard)
1.75, 2.0, 2.25, 2.5, 3.0 inch
4.45, 5.08, 5.72, 6.35, 7.62 cm
No change
Wind Load 17.5 sq ft / 1.63 sq m No change
Wind rating 100 MPH (EIA-222-C) No change
Adjustable elements 4 No change
Power Rating (40m-6m) 3 KW (80m) 1.5 KW
Feed points 1 1
Frequency coverage 6.8 – 54 MHz 3.4 – 54 MHz
Tuning Rate 1.3 ft per second No change
Control Cable 16 wire 22 AWG shielded 24 wire 22 AWG shielded
Performance for Ham Bands DB36 Gain DBi DB36 Front to Rear, DB
80M 1.35 n/a (pattern at right
angle to elements)
40M 7.2 21
30M 8.2 18
20M 9.3 22
17M 9.9 27
15M 10.2 27
12M 10.4 21
10M 10.7 11
6M – 4 elements 4 2
6M – with optional passive
element 50.0 – 53.3 MHz
12.8 27

The automated adjustment process allows the antenna to behave like a high performance mono-band antenna at any given frequency which results in superior performance.

We elected quite a few options for our antennas so we had a number of different manuals to read and understand. The options included with our DB 36’s are:

The first step in the assembly of the antenna is to read all of the manuals, inventory all of the parts and assemble and organize all of the tools and components.

SteppIR is constantly updating its antennas to improve their reliability, ease of assembly and appearance as well as the antenna’s overall performance. An addendum to the manuals was provided which explained how to properly apply all of the revisions. As you can see from the picture, there are quite a few parts which make up one of these antennas.

Parts Inventory and Tools

Parts Inventory and Tools (First of two DB36’s)

The first step in the assembly process is to bolt together the sections that make up the 36 ft Boom. We made a set of 4 ft high saw bucks to support the antenna during assembly. Several sets of carpenter’s clamps were used to keep the boom fixed on the saw bucks.

DB36 Boom

SteppIR DB36 Boom

The next step is to carefully mark the location of all of the elements on the boom. Precise measurements are important here if the antenna is to provide the best possible performance. As you can see from the picture, there are quite a few measurements that need to be made.

Element Spacing on Boom

Element Spacing on Boom (Courtesy SteppIR)

To make this job easier, we used cable ties to fasten a long tape measure to the boom so that we could mark all of the element mounting points accurately. We used a set of color pens to do this so the marks associated with each of the 6 elements were easy to identify. We used hose clamps to extend these marks to circles around the boom after marking all of the locations as shown below.

Element Layout on Boom

Element Layout on Boom

Each of the four adjustable elements uses a stepper motor housing that must be attached to the boom via a mounting plate and saddles. Three of the four elements are loops and these also require a return mounting assembly. As you can see from the diagram below, there is considerable hardware associated with each of the element assemblies. We took our time here to ensure that we did these steps properly. Most of the fasteners in the kit are stainless steel pieces and its important to use anti-seize lubricant (supplied) on these fasteners to avoid galling when they are tightened. We also installed the control cables inside each of the stepper motor housings prior to mounting them on the boom.

Driven Element Assembly

Driven Element Assembly (Courtesy SteppIR)

It is important to get each of the element housings level on the boom so that the antenna elements are straight and parallel when assembled. To do this, we first fastened a level to the mast plate adjusting eye bolt and leveled the boom. With this done, we used a second level on each of the element and return housings along the boom to ensure that all of the elements where level and parallel to each other.

Leveling Boom and Elements

Leveling Boom and Elements

This next picture shows the completed Driven Element Assembly after leveling and final tightening of the mounting saddles to SteppIR’s specifications using a torque wrench. Each saddle accepts a stainless steel set screw to lock one half of the saddle to the boom or the element extension tubes. These set screws are installed and tightened last, one in the accessible half of each saddle.

Installed Driven Element Assembly

Installed Driven Element Assembly

We next installed the other three element assemblies (the Reflector, Director 1 and Director 2) on the boom leveling them as we went. Each element has a slightly different configuration so its important to carefully follow the instructions in the manual for each one. We marked each element’s control cable with a colored pen every foot of so. These colors matched the color coding we choose for each element when we marked their locations on the boom – Red for the Driven Element, Blue for the Reflector, Green for Director 1 and Black for Director 2. This will make the wiring of the control cables easier and less error prone at a later step. Also, if the wiring needs service once the antenna is on the tower, the color coding is the only way to identify which control cable is associated with a given element.

Element Assemblies Installed on Boom

Element Assemblies Installed on Boom

With all of the element assemblies completed, we next installed the mast plate, boom truss support tube and the connector box option. The connector box option provides a neat way to correctly connect all of the elements control cables and the 80m dipole relay to the control cable down the tower to the controller in the shack. There is a threaded bolt/nut combination on the mast plate which allows easy leveling of the antenna once its installed on the mast.

Mast Plate and Connector Box

Mast Plate and Connector Box

The next step was to install the Phillystran boom support cables and turnbuckles on the boom truss. The turnbuckles are adjusted to keep the boom straight and level.

Boom Truss

Boom Truss

At this point, we have about three days of time invested in the assembly of our first DB36 yagi. The next step will be to assemble the element sweeps and support tubes. We will cover this and the additional steps needed to complete the assembly of the DB36 in a future post.

– Fred (AB1OC)

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