I needed a good portable antenna for my field kit. Something that packs small, is light weight, and easy to deploy. And as the old saying goes “Antennas can have high gain, high bandwidth, or small size. But you can only pick any two”. I decided to build myself a “Jungle Antenna”. All I need to deploy it is a few sticks and something I can hoist it up into (like a tree), to get to operational height.
The Jungle Antenna was used by the US military to boost the range of their smaller inefficient antennas on their radios. The Jungle Antenna was simple to build and would give them significantly more range with their radios. Another advantage for the military was the fact that it blended into it’s surrounds because is was made with some of natural material from the area.
Supplies you will need: (Paid Links Below)
- Split post BNC adapter (AKA Cobra Head)
- Wire (I used 14 gauge THHN, but you can use something else)
- Zip-ties
- Rope
- 3 sticks
- Tape measure
- Electric tape
- Marker
- Carabiner Clips (optional)
The length of the antenna will depend on which frequency you want to transmit on. The formula to figure that out is:
234/frequency in MHz = length in feet
Or you can do it the easy way and use an online dipole antenna calculator.
In my case, I want to transmit on the 2 meter amateur band (146.00 Mhz). 234 / 146 MHz = 1.6 feet
To convert that to inch, multiply by 12: 1.6 feet x 12= 19.2 inches
I then add 3 inches for loop at the ends: 19.2 + 3 = 22.2 inches
I rounded to 22.25 for easy measurement.
For a little better performance you can make the negative wire just a little bit longer (maybe 10%) than the positive one. You can also add in another ground wire and make it a square instead of a triangle.
Cut 4 wires to the length that you calculated. Strip each one back a ¼ of and inch and crimp ring terminals on the ends.
Measure 19.25 inches (use your calculated length) from the terminal out on the wire and make a mark. Bend the wire at that mark back on itself to create a loop and tape the wires together. Adjusting the size of the loops can help you tune the antenna.
Next hook one of the wires to the positive (red) end of the cobra head and the other three wires to the negative (black) end.
Cut three sticks about 30 inches long (depending on the size of your wires you made need to adjust the length of your sticks). Place them in a triangle shape on the ground and zip-tie together.
Next hook each of the negative wires to each corner of the triangle. The goal is for them to fanned out at about 45 degree angles.
Now hook a rope to the end of the positive wire and hook up your coax cable to the cobra head. Throw the rope up in the tree and raise the antenna. Keep it away from branches and the tree trunk for better efficiency. After your antenna is tied off you are ready to go.
