Quad Construction

One of the more troublesome aspects of quad construction is providing an effective support of the arms that hold the quad loops. Then there is also the problem of securing the quad loops to a suitable boom. Not that anyone would try to use an unsuitable boom but some have tried using unsuitable means of attachment. We are defining unsuitable as any method that does not allow the finished quad to survive at least one year of seasonal weather.

Consider the following.

Spiders to hold support arms can be made from short lengths of square metal tubing. These tubing pieces can be welded together at right angles. Additional strips of metal can be welded at right angles to these square tubing assemblies and used to secure the spiders to a boom. If metal booms are selected, the strips of metal serving as boom mounting tabs can be welded to the metal boom or the tabs can be drilled and mounted using sheet metal screws or more conventional nuts and bolts.

Use of aluminum or stainless steel is preferred but mild steel may be more readily available and weldable. A mild steel assembly can be protected by painting. A good brand of paint like Rustoleum is effective and economical with a single can of spray paint being enough to protect several dozen spiders.

The square tubing spiders are hollow all the way through allowing hardwood dowel ( or special hardwood square strips cut on a table saw ) to be used as spreaders to support the wire elements. The hardwood spreaders can be painted or boiled in paraffin to protect them from the weather. Or use plastic rods. The supports can be held in place in the metal spiders with screws driven through a tapped hole in the spiders or they can be glued in.

Practical dimensions can be relatively small for VHF quads. A two meter version could easily be implemented using 1/4 inch square tubing lengths no longer than 1 inch. Spreader arms would be less than three feet.

This method of construction can be scaled up for HF frequencies. Spiders made from 1 inch square tubing as short as 3 inches in length might be suitable for a multiband quad with 20 meters being the lowest band covered.

I would prefer to use square tubing because it is easier to make a square weldment using square tubing but there is no reason round pipe could not be used as well. In my case I would also select a square boom either metal or wood. The only construction material I would exclude is PVC pipe. I have seen too many projects that use PVC pipe and the only ones that look presentable are the collinear vertical arrays where the pipe only serves as a radome containing the antenna. All other applications have a distinctly tacky plumbers look to them.