Ve6fi Amateur Radio

 

 

 

Installing a HF Beam Antenna

Introduction

Installing a beam antenna on a guyed tower or a self-supporting tower can be a challenge. On a guyed tower one has to maneuver the beam around the guy wires and somehow get it on top of the guy wires. On a self-supporting tower one may not be able to pull the antenna straight up because of trees or buildings which are close to the base of the tower. In both of these situations a person has to have a plan that will allow the beam to get to the elevation on the tower without the antenna being damaged.

The technique described in this article will allow you to install a HF beam antenna in a safe and controlled manner.

General Concept

To install a beam antenna on towers as described one would use a single tramline and haul the antenna up on a pulley suspended from a tramline. A back guy is used to support the mast or the gin pole in a vertical position so that the mast or gin pole will not fail due to bending. As shown in the attached drawing the beam is suspended below the tramline and is pulled up the tram by a rope at the bottom of the tower. The beam is held level by two lanyards connected to the boom of the beam. If the elements have to be tilted upward, the tiller arm can tilt the antenna.

Detail Setup for installation on a self-supporting tower with space available at the base of the tower.

One would position the beam on the ground at the base of the tower and pull it straight up. The lift line would be kept as close to the tower as possible to minimize the horizontal forces on the mast or the gin pole. In this case one would not require a tramline.

Detail Setup for using a tram

Referring to the attached drawing, the tramline must be positioned so that it is above any guy lines that are attached to the tower. Usually the last set of guy lines are attached at the top of the tower. In that case you would require a mast that extends 8 ft above the top of the tower. The mast is the 2 or 2.5 inch diameter pipe that extends from the rotator to above the top of the tower. The beam is attached to the mast.

If one does not have a mast that extends eight feet above the tower one would install a gin pole at the top of the tower. For a gin pole one would use a 20 foot piece of 1.5 inch or 2 inch diameter aluminum pipe and chain it or web strap it to the tower so that eight feet of it protrudes above the top of the tower.

The top end of the tramline is attached to the top of the mast. The lower end of the tramline is connected to the hitch on your vehicle. (Shown as tramline anchor on the drawing). Connect the top end of the back guy to the top of the mast and connect the lower end of the back guy to a temporary anchor on the opposite side of the tower from the tramline. A come-a-long on the back guy should be used to apply some adjustable tension on the back guy. The tramline connected to the vehicle should be tensioned before the beam is pulled up.

Attach a pulley on the top of your mast. This is the pulley that allows the pull rope to pull the beam up the tramline. The pull rope is attached to the beam, as shown in the attachment. It goes through the top pulley on the mast and then goes through the bottom pulley at the base of the tower so that it allows the pull to be in a horizontal direction.

A tiller is attached to the boom of the beam. It is a lever arm that is attached to the boom and has a rope on the end of the lever such that the beam can be rotated, if necessary, to keep the elements tips elevated so that they do not interfere with the guy wires. In order to tilt the beam one would pull on the tiller rope from the ground.

Attach two tag lines to the boom of the beam about six feet from the center and attach the ends at the center of the beam (so that one can untie them later). One of the tag lines could be installed on the tiller arm. One ground person could handle both tag lines

Pulling the beam up the tram.

Pull up the beam by pulling the pull rope horizontally on the ground by a person, a winch, or a small tractor. Watch the mast so that there is equal and opposing forces on it. One may have to tighten or loosen the come-a-long on the back guy. Once the antenna is at the top one can loosen the tramline by moving the temporary tramline anchor (vehicle) towards the tower base. Then lower the beam to the height on the mast where it will be installed.

After one has the beam in place, disconnect the taglines but do not just drop them carelessly to the ground as they may wrap around the guy wires. Drop them to the ground in a controlled manner.

Conclusion

This is a controlled method of installing a beam antenna that requires some preparation. Following the above recommendation will allow one to install a larger or smaller beam antenna quickly but safely.

 

 

 

 

 

Denis ve6aq

Coolican@rac.ca

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