2 Meter Quad PVC Pipe Antenna
This is a different way of using PVC pipe to build a 2 meter cubical quad antenna. Instead of an "X" style spreader this antenna uses an "H" shape spreader.
The design is really quite simple and easy to make but it may take a little practice to get just the right square shape for the wire element. Once you get a feel for cutting the pipe it will get easier. It did take me a couple of tries when first experimenting with this antenna. Having some extra PVC pipe on hand would be a good idea.
The antenna is made of 3/4" schedule 40 PVC pipe. I used it instead of 1/2" pipe so that the pipe would be a bit more rigid. To help keep the boom rigid I used a piece of 3/4" wood dowel rod as a stiffener. You might also be able to coat the wood dowel rod with glue before inserting into the PVC pipe for added strength.
This antenna turned out to be very directional and it did take some time to get it pointed at a repeater that was located about 40 air miles away. It also took a little time to charge a battery for the camcorder in between takes, hi hi.
Measuring the PVC Pipe Spreaders
It is easy to understand that the lengths of each side of the antenna is approximately a quarter wave-length long but cutting the spreaders can be a bit tricky. Here is some advice to help.
The length of the PVC pipe for making the spreaders depends on the size and type of wire used to make the elements. To determine the spreader length you subtract the thickness of the wire where the wire bends at the edge of the PVC pipe on both ends of the spreader.
Bare stranded copper wire tends to flatten out when bent down from the edge of the PVC pipe while solid gauge wire does not. So the total spreader length for the stranded wire may be slightly longer than a spreader made for solid gauge wire. A spreader made for use with insulated wire will be cut even shorter than that made for uninsulated wire as you will need to also deduct the thickness of the insulation.
To measure an outside spreader, as described in the video, use a 1/8 wave length instead of 1/4 wave and measure just half the outside spreader.
You can begin by determining how much you need to allow for the bend in your antenna wire element. Use a scrap piece of the antenna element wire and bend the wire down over the inside edge of a piece of PVC pipe. Measure the distance between the end of the pipe and the outer edge of the wire at the fold and make note.
Place a piece of PVC pipe in the side opening of a Tee connector. Measure from the seam in the connector out along the PVC pipe for a distance of 1/8 of the total element length. Then subtract the amount needed for the wire to hang off the edge of the pipe and mark the pipe. Make three more the same size to make all of the outside spreader pieces for an element.
For marking the inside spreaders insert a piece of PVC pipe into a four-way or Tee connector, depending on which element you are making. Then again measure from the seam in the center of the connector the same distance as the outside spreaders. You will not only subtract the distance needed for the wire but you will also need to allow about 1/8" for the lip inside the outer Tee connector.
Tuning and Impedance
The only way to tune the antenna is to change the length of the driven element and remake the spreaders. I used an online cubical quad calculator to calculate the lengths for use at 146 MHz. You can see the results in the last video.
The antenna is not designed for use with a balun. Although a balun could be added it is not critical.