SteppIR BigIR Vertical Antenna
When we installed our new tower-based antenna system last year, I was forced to take down our SteppIR BigIR Vertical Antenna to make room for the tower. We really miss having the BigIR Vertical because it provided omnidirectional coverage on all of the HF bands from 80m – 6m and is a good DX antenna due to a vertical antenna’s characteristic low-takeoff angles. The SteppIR BigIR Vertical uses a stepper motor to move a length of beryllium tape up and down inside a hollow tube effectively changing the electrical length of the antenna to tune it. The antenna also has an optional Switchable 80m Loading Coil which allows the antenna to be tuned for the 75/80m band as well. The adjustment of the length of the antenna and the coil is handled by a controller in the shack which reads the frequency of an associated radio and automatically adjusts the antenna as the radio is tuned.
Antenna Layout Plan
We decided to re-condition and re-install our SteppIR BigIR Vertical in the woods in front of our house. This location was chosen as it provides adequate separation between the BigIR and our other transmit and receive antennas and is at a high spot on our lot. This area is also surrounded by some fairly wet ground which should enhance the performance of the BigIR Vertical Antenna.
Vertical Antenna Foundation
The first step in the installation of the antenna was to dig a hole for and pour a concrete foundation for the antenna. All of the needed materials as well as a rental motorized post hole drill were obtained at our local home supply store. We used an 8″ round form and dug down approximately 3 feet into the soil to set the form. We then placed about 6″ of medium stone in the bottom of the hole and filled the form with cement. We set and plumed a piece of 2″ plastic PVC pipe in the center of the form to hold the steel pipe that mounts the BigIR Vertical Antenna.
Foundation And Base Mounting Details
The PVC pipe is slotted on the ends with a saw so that it will clamp and hold the BigIR mounting pipe firmly in place with the aid of two stainless steel hose clamps. The mounting pipe that comes with the BigIR is slightly smaller in diameter than the inside of the PVC pipe so a few layers of electrical tape are used at three points on the mounting pipe to create a good fit. This approach allows the antenna and the associated mounting pipe to be removed from the foundation for use at another site if needed.
Vertical Antenna Radial Plate
The next step in the installation was to assemble and mount a DX Engineering Radial Plate. This Radial Plate is an excellent part and will make it easier to attach the planned 120 radial wires to the antenna. I am using N-connectors on all of the feedline connections associated with our BigIR Vertical so I also installed a N-connector Feed Through Connector on the radial plate to enable easy grounding of the feedline coax’s shield to the radial plate and antenna.
BigIR Pre-Assembly – Element Support Tube (EST) Joint Sealing
The next step in the installation was to re-assemble the BigIR Vertical Antenna. The paint on my element housing tubes had faded quite a bit so I lightly sanded them and sprayed them with a couple of coats of Krylon U-V Resistant Clear Coat. This made the tubes look like new and provides protection from fading and weakening of the element tubes due to the effects of UV radiation. SteppIR has made several enhancements to the BigIR since I purchased it a few years back. These include a much better sealing system for the element housing tubes which makes use of heat shrink tubing (pictured above) and a High-Wind Reinforcing Kit for the antenna’s element housing and base. These updated parts and components were obtained from SteppIR for use in re-assembling the antenna. SteppIR has also improved the assembly and instruction manual considerably.
BigIR Wind Reinforcing Kit With Element Housing And Coil
I first connected one end of a spool of 4 conductor control cable to the element housing and reassembled the antenna’s element housing, 80m coil, optional feedline choke balun and the wind reinforcing plate and saddles.
BigIR Pre-Assembly – Base With Both Sections Of Element Support Tubes
Next, I attached the lower section of the element support tubes to the base assembly. I also prepared the upper section of the element support tube by sealing the joints, attaching the guy rope bracket and installing the top cap/vent and rubber coupler. The antenna is over 30 feet in length when the fully assembled so its best to leave the antenna base/lower element housing tube and the upper element housing tube separated to make transporting the antenna to the site where it will be installed easier.
After transporting the pre-assembled antenna to the installation site, I next attached three lengths of Dacron Antenna Guy Rope to guy rope bracket on the antenna and assembled the two sections of the element support tube to each other, completing the assembly of the antenna.
Coupler UV Protection
It is a good idea to cover the rubber coupler which attaches the upper and lower element support tube sections together with several layers of electrical tape to protect the rubber coupler from UV damage.
BigIR Installed On Foundation – 80m Coil And Balun
Next I carefully lifted the antenna onto the foundation, attached the three guy ropes to their anchors and then torqued the saddle clamp bolts on the wind reinforcing bracket to 12 ft-lbs. It’s important to not over tighten the saddle clamp bolts as doing so can crack the fiberglass tubes on the antenna. The next step was to tighten the lower rubber coupling clamps, sealing the antenna’s connection to the metal tubing in the foundation.
BigIR Grounding Details
The last step in the antenna installation was to connect the ground lug on the 80m coil to the radial plate using a DX Engineering Ground Strap.
BigIR Installed On Foundation – Element Housing And Control Cable
The picture above shows the element housing side of the installed antenna. The spool of control cable will be covered with a plastic bag to protect it from the weather until the final feedline and control cable connections are run to the shack.
Guy Rope Anchor
The picture above shows the details of the guy rope anchors used to secure the guy ropes on the ground. Three Earth Anchors were turned into the soil using a steel rod which provides a solid point to attach the three guy ropes. The rope tension adjusters shown in the picture above were obtained from our local hardware store.
A Stealthy Vertical Antenna In The Woods
As you can see from the picture above, the BigIR Vertical is quite stealthy when installed in the woods. While it may not seem so, the work outlined here represents the easy part of a vertical antenna installation. The real work lies in installing the radial wire field around the antenna. The radial field has a significant impact on a vertical antenna’s performance in terms of both radiation efficiency and takeoff angle. The ground in our area is not very good so I am planning to install an extensive radial field consisting of 120 radial wires, each 110 feet in length. I will cover this part of the project along with the installation of the feedlines and control cables to the shack and the final integration and testing of our BigIR Vertical Antenna System in a future article.
- Fred (AB1OC)