Modify your Arrow antenna into an ultralight,
In my quest to reduce radio weight, I have been slowly modifying my Arrow antenna over the years. Having operated in nearly every type of summit weather I came to the conclusion I needed my antenna to have the following characteristics:
- Compact; easily packed into a backpack
- Lightweight but still durable
- Reliable and simple to operate regardless of the weather
- No tools required to assemble/disassemble; no parts to loose
This guide will give all the details to modify your Arrow antenna so the boom is lightweight and the antenna elements are secured together using elastic cord creating a “tent pole” type of connection.. No more bolts to loose, or confusion on what elements goes where. The elastic cord setup also makes assembly and disassembly fast and efficient.
Materials & Tools:
Depending on what route you go for the boom and elements will determine what materials and tools you will need.
- Pipe cutter
- Black Sharpie
- Multi Step Bit
- Sandpaper of various grits (80-220)
- Green Scotchbrite
Directions to Modify Your Antenna:
To start with, you need to decide what kind of boom you want. You have several options:
- Use the original boom that came with the antenna
- Drill out speed holes on the original boom (or other AL stock). See the W8LID guide for instructions.
- Use your hiking pole and 3D mounts. See my previous post on how to use this method.
- Carbon fiber boom. Build one yourself or contact Ken Alexander (VE3HLS) on Twitter about purchasing one.
For elements you have three options:
1. You can leave the elements in the original configuartion and add them to your new modified boom.
2. You can make your elements seperate (threaded) in the middle (as they come from the OEM), and add elastic cord to the other sections. I have not personally done this mod however you will need to use pins to secure the cord inside the elements.
3. I chose to go with the entire element threaded with eleastic cord and used custom inserts to make the whole element collapsible.
Going with #3, you need to cut new arrow shafts to match the legth of each element. Next, cut each element in half (if desired). This will allow each element to be around 12-14″.
The hard part of this whole project is to remove the original element out of each gamma match (2M & 440). You need to remove the coupler and then place the gamma match element inside a pipe. Thread in a bolt and give the bolt head a series of good blows. The element is held in by friction in the gamma match and should come out. Once it does, insert the new arrow shaft element.
When you cut all the elements, the pipe cutter will collaspe the hole and will require you to re-open it back up. I use a step drill bit by hand to open up the diameter of the shaft so it will accept the inserts.
The inserts will have to be made by hand. If you have a lathe, you have it easy. I didn’t so I just chucked each insert into a drill press and sanded it down using 80# followed by 120# and 220#. You will need to size the insert so that the permament end is held in place by friction.
For the insert that goes thru the boom:
- 54.30mm in overall length
- Permament end is 6.30 mm in diameter & 15 mm in length
- 6.18mm diameter & 39 mm in lengthfor the removable end
For the insert that connects the element pieces together (and not the boom);
- 37mm in overall length
- Permament end 6.30 mm in diameter & 15 mm in length
- 6.18 diameter & 22 mm in length for the removable end
*Mesurements are rough numbers and you should shape the inserts based what fits best for you.
Once you have the inserts in place, you need to run elastic cord thru all the elements and tied off at each end with a 3D printed end cap.
For more pictures on the project, check out my online album.