Building a Tri-Band DipoleBy Jose B Rivera - N2LRB
June 18, 2013 - This is a short article of my building a tri-band dipole in March of 2007. After trying out a dipole on 20 meters I decided to construct a tri-band dipole made up of three dipole into a single feed line. I wanted the dipole to work on 20, 17 and 6 meters. I purchased the following items.
- three dozen ruler some with holes already in them
- 30 nuts and bolts (three for each ruler, one per band)
- 30 wide washers to hold the wire in place
- enough speaker wire for three bands
- Polyurethane to weather proof the wooden ruler.
- Alpha Delta Dipole Center Connector
The first thing I had to do was to apply polyurethane to the wooden rulers to keep moister from seeping in and rotting them. I applied one coat and then put them out to drive outside our apartment door, in the stairwell. They dried over night and were then ready to use. I then cut the speaker wire for lengths appropriate for 20 and 17 and 6 meters. An identical set for each band. I started out attaching the wires to the rules in my apartment as some rain kept me from working out of doors.
It was difficult to initially keep the wire attached to the rulers using the nuts, bolts and washers as they kept sliding off. It turns out that tightening the nuts helped. Since the antenna was wider than my living room I had to create it working on one half of the antenna at a time. After completing one side, of the antenna I noticed that carrying just one side up the stairs to the roof was be a problem. There was no way to compress it without having it tangled. And it wasn’t till later on that I figured that winding it on a cylinder form would have been the best way to transport it.
I dismantled the antenna and took the parts up to the roof where I attached one end of the longest wire to the roof wall and proceeded to add the rulers. The rulers act a separators between the three wires. I was able to complete one side of the antenna, but the rain and wind kept pulling it apart. I left the antenna parts on the roof floor and hoped the next day would bring better weather and another opportunity to complete the antenna.
The next day was a typical early March day, cold and dreary, but no rain. After work I immediately set to complete the antenna. I had to work quickly before the sun set. So I have about an hour an a half in which to build the antenna. Again I attached one end of the longest wire on the roof wall and added 5 rulers to it. No problems. I then added the second and third set of wires to the rulers. One side of the antenna was complete! The second half of the antenna was easier and took less them than the first half to complete. My Tri-Band Dipole was complete after attaching the Alpha Delta Center Connector to both sides of the dipole wires and added the coax cable.
I attached the Alpha delta center connector to a 10 foot mast and then raised the mast. I then connected the mast to the vent pipe. It was time to test the antenna. I connected the coax from the tri-band antenna to my antenna MFJ-993B Automatic Antenna Tuner and turned on my Kenwood TS-2000 transceiver. I immediately began to hear other hams on 20 meters. I made a few contacts! The antenna worked! It was great realizing that I could build a workable tri-band antenna.
After a few days I added a few improvement to my tri-band antenna. First I purchased short bungy cords and attached them to both ends of the dipole to allow it to give a little in the wind. It also provided a better way to remove any one side from the roof wall in order to re-attach any ruler that came loose from a nut and bolt. I also added a male connector to the longest wires and put a female connector to the extra wire in order to increase their length in order to work 40 meters.
I used this antenna for about two weeks before taking it down and trying out whips and a G5RV. In the end it was easier to use and maintain a one wire dipole. But it was a lot of fun
building and using my short lived tri-band dipole.