Appalachian Trail Antenna
Note: I made a small change in the assembly of the BNC into the tee. This way you will not have to worry about epoxy running over the BNC connector. I built another tee on July 6 and I found an easier way of creating the water proof tee. Please re-read the building instructions. This was updated on July 8, 2001.
Over the past several months a group of EPA QRPers have been hitting the Appalachian Trail with our QRP radios. We have been experimenting with different types of antennas on the AT. We have come up with a light weight and rugged design that we want to share with our fellow QRPers that head out into the great outdoors.
We are using a light weight mono-band dipole for 40 meters. The antennas is made of copper clad steel wire with a strong, tough PE insulated jacket. This wire is perfect for hanging in that not so perfect tree that can rip or break normal copper wire. This is a #26, 19 strand "Stealth-invisible" copper clad steel wire which can be purchased at RF Davis. The center insulator with a wire strain relief for each leg of the dipole and a BNC connector. Take a look at the picture of the 40 Meter Dipole. Since the antenna is cut for 7.040 MHz. I wanted to try making this antenna work on all bands. I found some 300 ohm mini-ladder line, 2nd picture, I found at a hamfest and created a different type of feed for the antenna. Now I have a 66 foot doublet that plays great on all the bands including the WARC bands.
This antenna works great on the AT around the 1,100 foot level. I usually have it hung only 8 to 10 feet off the ground and I can work all over the East Coast on 40 meters. I receive good signal reports for only using 1.5 watts output on 40 meters during the day with the Small Wonder Labs SW-40+ transceiver. When I use the 25 feet of the 300 ohm feed line and a tuner, I can work into Europe on 20 and 15 meters.
To create the antenna tee that is shown in the 40 meter dipole above is very simple. The parts list to create the tee is as follows:
#1 - You will need a 1/2" PVC plumbing tee that can be found at your local home improvement store.
#2 - One tube of 2 part clear epoxy, the clear will flow better than the dark epoxy. I use Loctite 5 minute clear epoxy.
#3 - Three small eye hooks.
#4 - Chassis mount BNC connector.
#5 - Cardboard, wax paper and duct tape.
First you must prepare the BNC connector by connecting 6" of wire to each side of the connector. Next you must drill a 1/16" hole in the center of the PVC tee for the top support eye hook. After you drilled the hole insert the eye hook into the hole. Twist the hook in to the tee just enough to make threads in the hole. Un-screw the hook, then measure how much of the threads on the eye hook must be removed so that when you have the hook inserted into the tee it will protrude the inside of the tee by 1/16". This will not interfere with the wire inside the tee but it will allow the epoxy to firmly adhere to the threads and secure the eye hook for support of the antenna. Cut out a piece of cardboard to cover the center and one end of the tee. Try to make them the same size as the outer O.D. of the tee. Glue wax paper to one side of each cardboard cut out. This will give you a smooth cardboard free end. If you don't want to use the wax paper, the cardboard will adhere to the epoxy and you can't get it off of the tee. Carefully place two small holes into the cardboard that will go onto the one end of the tee. The holes should be evenly spaced.
Slide the cardboard over the wire and BNC connector so it will touch the bottom of the connector. Now insert the wire and BNC connector through the bottom of the tee. Pull each wire through the opposite ends of the tee. Now take the one wire and put it through the lower hole in the cardboard. Take a small strip of duct tape about 1" wide and 3" in length and secure the cardboard over the end of the PVC so there is no space for the epoxy to run out. Next make sure the BNC connector is flush with the bottom of the middle hole on the PVC tee. Now you will have to take the other cardboard cut out for the middle hole and carefully cut a hole so it will slide over the end of the BNC connector. This is very critical to have the BNC connector flush with the cardboard. Secure the cardboard with another piece of duct tape as described above. Take another eye hook and place it into the first end of the tee that you have prepared.
Place the tee into a vise with the open end facing up. You should have the other wire coming out of the tee. Now you will have to mix your 2 part epoxy into some type of container that has a corner so you can pour it into the end of the tee. You might want to put some paper under your tee before you pour the epoxy. Carefully pour the epoxy into the open end of the tee. Watch for any leakage around the cardboard sealed ends. Fill the tee to the top of the open end. Wait a minute and make sure the end is even with the tube. Position the wire in the end so that is it identical to the other side. When the epoxy is a little hard, insert the last eye hook into the end to match the other side. Let the epoxy cure before you handle the tee.
When the epoxy is cured enough to handle you will need to take the cardboard off the other ends. Read the instructions of the epoxy to calculate the time when you will be able to handle the tee. Check to see if the BNC connector will fit securely to the female BNC connector in the tee. Now take an ohm meter and identify the center wire. Place tape or mark the tee so you know which end is going to the center of the feed line. Take one end of the antenna wire and tie two knots onto the eye hook. Then do the same on the other side. Now with the wire coming out of the tee cut it to about 2" past the epoxy. Make your connection to the antenna wire by soldering and then tape the connection. Now you are ready to cut you dipole to your desire length. If you want to make a doublet, make sure each leg is the same length. I used 1/4" wooded dowel to make my end insulators of the antenna, this low weight insulator works good.
So if you are having some trouble, please send an e-mail to Ron, N3EPA, and ask him your questions.