Are you a plumber ? Interested in pluming or sweating copper tubing? How about antennas and the six meter band? Well if you answered yes to any of the above you may be interested in the following.

Below is a drawing of a six-meter squalo or square halo, which is just a 1/2 wave dipole bent into a square or near square shape that is. When you bend the 1/2 wave dipole in a square it has several effects on the impedance of the antenna as well as the pattern. The pattern is what we want but the impedance is not, there fore we use a parallel line tuning stub to get to the 50 ohm 'or close' feed impedance we want and need. The antenna is fabricated from 1/2 inch rigid copper tubing and elbows. All dimensions are from center to center of the tubing.

Some folks have a problem with the center to center measurements so here is a simple way to do them. First both objects must be of the same width/diameter for this to work.

To get the center to center measurement just measure from the inside of one object to the outside of the other and this will give you the center to center measurement, simple once you think about it.

The shorting bar is a strip of copper strap clamped around the tubing with screws. The main thing is it must be adjustable in order to tune the antenna and mechanically sound, you don't want it moving around! One other thought it must also be of sufficient size to carry the current of the transmitter. I would suggest a 1/2 inch wide strap.

I do not recommend this antenna for mobile use; it is just to heavy for one and copper will work harden if subjected to vibration then break. It's not a good thing to have part of your antenna falling off while driving down the road. John is running one on his truck so we will see just how durable the beast is.

The initial design for the antenna was calculated using a modeling program on the computer. The final dimensions were derived by the old try cut try method by John KG4OSA.

Thanks John for all the work on a cold November day, Ben.

Assembly:

First I highly recommend you build a jig for the antenna. This is a must if you or your group wish to build more than one. Below is the jig John built for his project after attempting the first antenna without one.

The jig consists of a sheet of plywood or paneling with cleats fastened to maintain the proper dimensions of the finished project. The corners are cut off the sheet to allow access to the elbow to tubing joint for soldering while in the jig. This will ensure the antenna dimensions are maintained while fabricating.

The antenna is fabricated using 1/2 inch rigid copper tubing and elbows. The spacer for the gap is made from two pvc couplings and a short peace of 1/2 inch pvc pipe. This was John's idea by the way, good idea John.

 Note: while the antenna is in the jig fit the two pvc couplings on the antenna then cut a peace of 1/2 inch pvc pipe to length to maintain the 2.5 inch gap between the ends of the copper tubing, this spacing is critical to the operation of this design.

 A word about the feed point 'where the coax is attacked to the antenna'. This initially needs to be adjustable then fixed after final tuning. One way to do this is to use hose clamps for the tuning phase then remove the clamps and solder the coax directly to the antenna before sealing and installing the antenna.

One other thought. Drill a 1/32 inch hole in the bottom of each elbow to allow water to drain out of the antenna. I guarantee you you can not keep water out of the tubing so the weep holes are required.

Take a good look at the photo of the antenna on John's truck. Pay attention to the coax and the way it is connected to the antenna. This is important!
This is still in the testing phase and the coax has not yet been final dressed.

On the final dressing let the coax drop down away from the antenna about 6 inches then forming a loop back up to the mast to the mounting point, secure the coax to the mast at that point. You are feeding a balanced antenna with an un-balanced feed line  'coax', and will create some problems.  There will be common mode currents on the coax. That being sed it should not give you any trouble if the coax is dressed correctly. In the event it does just wrap several turns of coax around the support mast to form a choke. How much you say? Just wrap until the trouble goes away. All joking aside it will depend on the installation and the number of turns will very.

Below is a photo of the antenna on the jig ready to be mounted and tuned. Note in the below photo John used a strip of stainless and 2 copper tubing clamps for the shorting bar. This is a good idea in that it adds rigidity to the antenna to help maintain the shape and reduce flexing.

Well that's about it, break out the tubing cutter, torch and do a little plumbing.

This antenna was A/B tested against a brand X sq. loop on johns truck. This antenna was consistently one S unit better than brand X at as close as 2 miles and out to about 60 miles. The pattern was consistent at the 4 cardinal directions front, side, back and side, no observed nulls in the pattern.
So it appears this is not a bad performer for a home brew antenna.

My thanks to John KG4OSA for building this antenna supplying the photos and allowing me to add this to the web site.
Ben

How about stacking these for base operations? well just click here.

Pattern for the squalo, 30 feet above ground