2m/440 Antenna

This is my version of the project first printed in the August 2006 QST. Below is sketch with antenna dimensions. Shown at right are pictures of my version during construction and after it was enclosed in a 3/4 inch PVC pipe. I used 1/2 inch copper pipe for the radiating elements and a nylon spacer for the center. To secure the spacer in place I used a brass machine screw and polyurethane glue. Performance of this antenna is as advertised in the QST article. The SWR stays under 2:1 for all of my repeater operations thus far (I do not yet have a 440 radio to test it on that band). I especially like the size advantage it has over a J-pole as well as its performance and toughness advantages over the 1/4 wave groundplane (made of solid 12AWG wire) I had been using.

Buddistick Experiments

The Buddistick is the vertical version of the Buddipole antenna system. Below is a picture of my Buddistick erected at Field Day '06 for use with my PSK31 station (I mounted it on a 5 foot section of PVC pipe guyed to the ground). Tune-up is simple enough in theory, just move the tap lead up and down the coil until you hear the signal to your receiver reach a maximum volume. Place a coil clip on that spot and check the SWR of the antenna. In practice, it is much easier to use an antenna analyzer (ie. MFJ 259B) to find the best tap position. For Field Day I set it up for 20 and 40 meters and achieved a good match on both bands.

20 meter Groundplane (part 2)

The base of the support pole is made of a ten foot piece of 1.25 inch schedule 40 PVC pipe that was cut in half for easier transport in my car. It is joined in the center by a 1.25 inch PVC coupler. Mounted on top of the PVC pipe is a 13 foot extendable fiberglass fishing rod which I purchased at Gander Mountain (I had originally planned on using a 16 foot rod but none were available when I went to the store, with additional height the radials can be lowered at a steeper angle which in turn raises the input impedance closer to the desired 50 ohms). I joined the fishing rod to the pipe by first removing some of the plastic at the base of the fishing rod so that it could slip inside the pipe. Next I drilled a single hole through the pipe and rod so that I could secure the two pieces together using a small bolt and nut to prevent the rod from sliding further into the pipe. This method for joining the pipe and rod is shown below left. I also wrapped the fishing rod with some electrical tape to compensate for the difference in diameter of the rod itself and its plastic base (this allows the rod to fit snugly inside the PVC pipe thereby stiffening the rod and pipe connection).

The radiating element and both radials are 16.5 foot long 14 AWG insulated stranded copper wire. For ease of assembly I soldered the radiating element to the center of a SO-239 connector and attached solder lugs to the radials. This allows me to attach the radials to the SO-239 with two small bolts passed through the holes on the connector, simplifying construction in the field. I taped the radiating element to the pole prior to raising the antenna. The radials were attached after the antenna was erected and securely guyed since the feed point is only 5 feet off the ground providing easy access for mounting. A photo of the feed point assembly is shown above right. From start to finish assembling the antenna and guying it in place took about 30 minutes to do by myself (with more people it could easily be erected in 5-10 minutes).

The performance of this antenna was better than expected. It matched perfectly on the lower end of 20 meters despite being cut for the center of the band (this is due to my use of insulated wire which adds capacitive loading to the antenna, electrically lengthening it). Whether you are looking for a solid performing base antenna or a light, compact, portable antenna this may be the project for you.

20 meter Groundplane (part 1)

Most hams are familiar with the quarter wavelength ground-plane antenna design. It is often the first antenna they buy or build for use on 2 meters after receiving their technician license. It is a well performing design that exhibits low input impedance, making it ideal for use with ham equipment without the need for special matching techniques. The antenna is easy to construct and due this simplicity is also highly economical. When considering the type of antenna to build for field day to use with my PSK31 setup this design was the obvious choice. It provides both low take-off angle and omni-directional radiation, allowing me to maximize my operating capability from a simple station. The antenna is made up of a single pole which supports the radiating vertical element and is guyed in place with nylon rope. The two radial elements are spread out and held in place by ropes. The layout for the antenna and the support pole is shown top right and a photo of the completed support pole guyed in place is shown bottom right.

2 meter J-Pole Antenna

This is perhaps the cheapest gain antenna for 2 meters that can be built. Total cost for this antenna is under $10 (excluding coax) and it can be built in about an hour. Using was is called "Plumber's Delight" construction I soldered all joints using a propane torch, lead-free/non acid core solder, and some soldering flux. While there are several iterations of the J-Pole that can be built, I liked this one because it does not require the builder to directly solder the coax to the copper pipe. Instead, a SO-239 is soldered to the T connector and a short piece of wire (I used insulated #12 stranded copper) is soldered to the center conductor to feed the driven element. My version of this antenna is mounted on my chimney and works very well, providing 2:1 or better SWR on the entire 2 meter band. It is incredibly strong and I have experienced no problems with wind or other weather.