I’ve been enjoying ham radio, going into parks, putting up an antenna, and contacting people at a substantial distance using very little power (“QRP”). I enjoy building antennas for this activity, and I designed one that I particularly enjoy using. This antenna lets me use any ham radio band from 40 meters to 6 meters.
This whole antenna system weighs only 286g and fits into a small gear bag with my radio. I can lift it with a long “crappie pole” or similar light, collapsing mast weighing a few hundred more grams, or throw a slippery, non-damaging line up into a tree (where that’s allowed) and pull it up by a cord. I let the ends be lower than the vertex, deploying it in a classic “inverted V,” varying the angle of the V and the deployment plane depending on the site and my goals.
It’s made from five 3D-printed parts, with some wires, connectors, hardware, and elastic cord attached.
I’ve tried to write detailed enough instructions for you to build your own. If I’ve been unclear, please comment and let me know!
Design
My prior design was a fairly typical X-shaped design, but the wire wrapped tightly around the edges, and some “kite wire” should not have a tight bend. Therefore, I made this winder that puts a 10mm minimum radius bend load on the wires to keep from damaging them from repeated deployment and stowing. It supports this minimum radius when stowing the wire in a figure-eight wrap that avoids introducing twists in the wire.
Each side of the winder has rails to hold one leg of the dipole, keeping them separate so that they don’t tangle. The links are made from bullet connectors instead of the more typical alligator connectors, which makes them compact and neat, and makes it easier to measure a precise length and tune the antenna for the exact frequencies you want to favor.
I used FreeCAD to design it, and you can change the design for your own purposes if you like. All the necessary files are included at the end.
Bill of materials
Besides choosing one of the step files and printing five parts, you will need:
- Enough antenna wire for the bands you want to support.
- I used DX Engineering copper-coated steel kite wire.
- I previously used, on an earlier version, silicone-insulated hookup wire, but the silicone tangled in twigs and the wires broke.
- You could use PVC-insulated 24AWG hookup wire.
- If you use vectran-core DX Wire UL or carbon-fiber RSE line you will need an alternative way of manufacturing the links that does not require soldering the wire, described but not yet tested as of this writing
- 2mm banana plugs
- The smallest ferrules that fit your wire, probably 0.5 mm, and a hexagonal crimp tool that usually comes with a starter kit of ferrules.
- 4:1 (or at least 3:1) marine adhesive heat shrink tubing, 3/32”/2.4mm, typically supplied in in a kit. The adhesive is a critical element of this build. The antenna will fall apart without it.
- Dacron kite line or similar (not kevlar because it is abrasive; not spectra/dyneema because it is too slippery).
- 1/16" shock cord
- Optionally, an FT-82, FT-114, or FT140 ferrite for a choke
- If you add a choke, print the correct files for the choke you choose
- If you do not add a choke, choose the files based on the size winder you want; FT-82 is the smallest and will require more turns of the antenna wire to stow; FT-140 is the largest and will require fewer turns.
- Coax
- If you are making a choke, use RG316 coax (thin, low loss for its size, solid PTFE dielectric) for at least the choke.
- Coax termination; either:
- A SO-239 or BNC bulkhead connector and four matching m3 screws (in which case you will have to print the correct base for the connector), or
- Your preferred termination at the end of your preferred length of coax, if no termination on the winder itself (in which case it does not matter which termination style you print).
- 5.8mm / 0.22” heat-shrink printed labels (or you can write on light-colored heat shrink tubing)
- Some cable ties
- Stainless or brass hardware:
- 4x M3 washers, preferably wide
- 2 M3x12 countersink screws
- 4 M3x12 or M3x16 socket cap screws
- 6 M3 nuts (use standard nuts with thread lock with M3x12 screws; can use nyloc nuts with M3x16 screws)
Build instructions
These instructions describe how to make a linked dipole. You can (of course) use this design to build a single-band dipole, or an end-fed with an integrated counterpoise (that is, a very-off-center-fed dipole) with a “random” 9:1 integrated unun or resonant 49:1 or so unun, or an off-center-fed dipole with a 4:1 unun, in the center hole originally designed for a choke. If you are interested in these variants, comment if you need help planning such a build.
Print your chosen configuration
There are six provided print files in STEP format. Each print file contains all five printed parts in the correct orientation for printing. Use organic (“tree”) supports for the unsupported overhangs. The design is intended to not require a high-end, highly precise printer. You should be able to use any common filament, though if you use PLA you probably want to use a toughened PLA (PLA+ / PLAPro etc) to avoid damage. I use ABS. PETG will be a fine choice. No need for extremely fine layers; 0.2mm should be fine, and a thicker initial layer should do no harm.
Do not assemble the pieces yet!
Build your (optional) choke
The hole is sized for a tight fit around your chosen ferrite and 0.1” RG316 coax. I recommend and use a typical 7-turn common-mode choke. Three turns in one direction, cross over, three turns in the opposite direction. The crossover provides two benefits: better high-frequency performance, and the coax exits roughly opposite where it enters. From G3TXQ Steve Hunt: High performance common-mode chokes this image shows the windings. (However, you will want to pull them more tightly around the ferrite. This is safe with RG316 due to the solid PTFE dielectric.) Use cable ties where the coax enters and exist the toroid to keep it tightly wound, as shown.
If you are using an integrated bulkhead connector, this choke only needs short stubs of coax on each end. If you are instead using an integrated feedline, this should be at one end of the wire with only about 5 cm / 2” of excess wire at the end.
Strip the outer insulation from the coax to within about 2mm of the ferrite. Separate the strands of the shield from the center, still in the dielectric, and twist it into a wire.
Put the assembly into the center hole in the large base part, with the stripped end towards the loop at the top of the base, on the top surface as printed. The bottom as printed has countersink holes as highlighted for the terminal screws; you want the coax on the other side, because it will be mounted to the antenna wires with washers being held by nuts on the other side.
This is the side that you want the short end of the coax on, pointed toward the loop:
The wires will later go around the screws, on top of the first washer:
Don’t actually put the screws and washers in place yet!
The other, longer end of the coax should be on the bottom side, the other side of the base plate.
Now use cable ties to lock the choke in the middle of the hole, using the four provided cable tie holes highlighted here:
Now that the choke is locked in place, put an M3x12 screw and washer in place temporarily. Strip the dielectric off the center conductor to the edge of the washer. Remove the screw and washer.
The other end of the coax
The other end of the coax, which exited the hole on the other side if you are using a common-mode choke, or may be on the same side if you are not using a common-mode choke, either goes to a bulkhead connector, or exits off the bottom and is fixed in place.
If you are using a bulkhead connector, screw it into the provided screw holes (they are designed to take an M3 machine screw without needing to be tapped). Then attach the long end of the coax to the connector without leaving extra coax in place. You may use cable ties in the round holes here highlighted to hold the coax in place.
If you are not using a bulkhead connector, use cable ties in either or both of the sets of holes highlighted below. Use reasonable tension to hold the coax in place without damaging it
Here’s how mine looks, assembled:
Finally, the antenna itself
Every time you cut wire for this project, cut two wires as close to exactly the same length as you can. When cutting the wires initially, keep them the same length. When trimming them, remove exactly the same amount. When cutting the wires off the roll, I matched them closely to each other, measuring the second wire I cut against the first. When trimming them to tune then to frequency, I used a ruler to trim precisely the same number of millimeters off each time I trimmed.
Cut two pieces of wire that are a bit longer than you need for the highest band you want to support. For example, if you want to support 6 meter operation, cut two pieces of wire a bit longer than 1.5m long. Strip them 1-2cm long.
Insert two m2x12 countersink screws into the terminal holes, and put a washer on each one.
Wrap the shield wire and one antenna wire around one screw, with both windings clockwise. Hold it in place, add the second washer on top, then screw the nut down to clamp them together. You want the wires touching and being clamped solidly together by pressure between the two washers.
Repeat that with the center conductor and the other antenna wire.
Now weave the initial wires through the three chamfered wire holes next to the terminals. One wire will go through all three holes, and the other through only the second and third. It does not matter which wire goes on which side, but ultimately one wire should come out on one the back and the other on the front. This is key to being able to wrap the wires correctly in the end.
Use cable ties to hold those wires in place using some or all the four pairs of rectangular holes marked below:
On mine, it looks like this. Because this is copper-coated steel, it’s fairly stiff, so I didn’t use additional cable ties. If I were using PVC-coated copper, I probably would use two on each wire.
Before starting to tune and add linked segments, add the winding rails. Use two socket cap screws, two m3x12 or m3x16, and two m3 nuts per set of rails.
Tuning and assembling links
Hoist the antenna in an appropriate environment (outdoors), and hold the two legs out to form a 90–120° angle. I use alligator clips at the end of cord connected to weights to pull the legs out, but you can use anything that can hold them out without affecting your test. Use an antenna analyzer or nanoVNA to trim them to your intended, preferred frequency for the band. When you cut the wires, always measure and cut exactly the same amount from each leg, measuring in millimeters. Errors will stack up, so minimize them by working with precision!
After you get the frequency you want, each time you intend to add another lower band, trim off another 8mm! That 8mm will be replaced by a banana connector as you prepare to add the next link! (If you accidentally trim off 8mm too much, relax, you are about to get it back.)
You probably want to take the antenna back down to add the next link. I did.
Add a full piece (roughly 45mm) of marine heat shrink tubing, followed by a heat shrink label for the band you just cut, followed by about 25mm of marine heat shrink tubing, to each wire. Strip 4mm from the end of each wire. Remove the insulation from two ferrules, and crimp them to the end of each wire, then cut them back to 4mm long. Take female bullet connectors, and solder the ferrule into the short opening in the connector. The ferrules should prevent excessive solder wicking into the wire.
(Option: Especially if you have non-solderable wire, strip 1cm of insulation. Remove the insulation from the ferrules, but solder only the ferrules into the bullet connectors, then crimp them onto the wire after they have cooled.)
Shrink the 25mm of heat shrink tubing over the female bullet connector and wire. As it cools, try to keep it lined up just over the end of the bullet connector as insulation. After it cools, move the label heat shrink over the shrunk tube above the bullet connector and shrink that in place.
Cut 18cm of dacron line using a hot knife or plasma lighter to keep it from fraying. Do not tie a knot. Slide the line through the 45mm of heat shrink tube not yet shrunk. Leave about 25mm of dacron between the end of the long piece of heat shrink and the shrunk piece around the bullet connector. You are looking for something like this:
Cut your next links generously and to exactly the same length as each other. Use a ~20mm piece of heat shrink to cover only the base of the male banana connector, but otherwise make it like the other end. You will end up with something like this:
Now connect the two bullet connectors, and pinch the last piece of 45mm heat shrink to hold a bit of extra wire with the dacron string in tension. You want something that looks like this. Much more and you’ll end up tangling; much less and it won’t wind well and will be harder to pull apart. Make the links for both legs as close to the same amount of bow as you can.
Now hoist your antenna, trim the next section, trim and extra 8mm for the banana connector, and repeat.
Option for flexible tuning
I built my antenna tuned for the CW portions of the bands. However, if you tune near the top of each band, you can carry a set of small stub wires of varying lengths on bullet connectors, and plug them in place of the rest of the antenna to tune lower in the band. Use fairly stiff wire (copper-coated steel kite wire is excellent for this purpose regardless of what you use for the rest of the antenna) and make whatever lengths you want. This will let you tune in the field for the lower portions of the bands by adding a stub of the appropriate length to each arm. (I work CW almost exclusively and the tuner in my radio is good enough if I want to work SSB, so I tuned for CW. Therefore I don’t have pictures of stubs to show.)
Tying out
In order to tie the ends of the dipole out in the field, cut two sections 5 meters or so of the thin elastic cord, and use two more pieces of 45mm marine heat shrink to join the elastic cords to the ends of the last links. Again, a plasma lighter will cut the shock cord without fraying. (If you want to be able to add stubs, you’ll need a female bullet connector at the far end.)
Stowing
For each leg, start winding around the side of the support rail nearest where the wire comes out of the strain relief holes in the base piece, and wrap in a figure-eight loop. (If you don’t use a figure-eight wrap, you will put twist into your wire and it will tend to tangle.) It will start looking like this:
Be gentle with the links especially where they go around a bend. When you finish wrapping the wire, it should look something like this:
The elastic cord can be wrapped in a loop rather than the figure eight, because it can accept the slight twist without damage, and that makes the whole package less bulky. Wrap one side all the way around. You can lock the end by stretching it around the top of one rail.
For the other side, wrap the antenna wire, and start by wrapping just a turn or two of the elastic cord, stretched lightly. You should see this:
If you have a bulkhead connector, just wrap the second elastic cord the same way.
If you have an integrated coax, wind that up with a very small under-over “roadie wrap” to avoid twists in it (it does essentially the same thing as the figure-eight wrap) into a loop about the same size as the winder, and position it on top of the second side. Run the loose end of the second elastic cord around both sides of the loops:
Finish by wrapping back and forth across the whole loop, tucking in the loose end of the coax neatly for the last few turns. This will snug up the loop to fit the winder.
Wrap the loose end of the cord once or twice around the rail on the other first side of the winder to finish, letting it lock lightly in place:
This neat package is ready to stow.
Deploying
When unwinding the legs, take it slowly and flake each leg out away from the other to avoid tangling, as you would with any wire dipole. Unpack the coax carefully to avoid knots. (If you undo it backwards, it ties a series of half-hitches that you need to carefully untangle.)
3D Printing Files
If you add a common-mode choke, I suggest the FT82, the smallest ferrite, because a dipole should have very low common-mode current; many people don’t use a common-mode choke at the antenna at all. It will protect against some RF coming down the coax, though, in case of a broken or misconfigured link. However, FT114 and FT140 are also common sizes. Note that if you use the larger ferrites, the base has to be larger to compensate. So if you care about size and weight, I strongly recommend the FT82.
All of these files assume 0.1” RG316.
I recommend strongly that you never wind a choke with foam-dielectric coax, and even solid polyethylene is subject to “creep” that can change the characteristic impedance and even short after a long time. Solid PTFE (Teflon) dielectric is the most resistant to these problems.
BNC
If you put coax termination on the device, BNC is smaller, lighter, easier to attach and detach, and handles more cycles.
BNCPrintAssembly-FT82-RG316.step (707.2 KB)
BNCPrintAssembly-FT114-RG316.step (709.0 KB)
BNCPrintAssembly-FT140-RG316.step (709.4 KB)
SO239
If all your existing coax is SO239/PL259, then you might as well make this compatible.
SO239PrintAssembly-FT82-RG316.step (722.5 KB)
SO239PrintAssembly-FT114-RG316.step (723.5 KB)
SO239PrintAssembly-FT140-RG316.step (724.0 KB)
FreeCAD
This design is parametric and allows you to make many more changes. Feel free! These files were created with FreeCAD 1.1RC but will probably still work on FreeCAD 1.0.
LargeRadiusWinder.FCStd (7.5 MB)
SO239PrintAssembly.FCStd (130.5 KB)
BNCPrintAssembly.FCStd (130.1 KB)
What is documented above is a wire dipole, except that it has links so it can work on multiple bands instead of being single-band. But if you don’t add any links, then it’s just a easily portable dipole. If all you work is 20m, then just make a 20m dipole and don’t add any links.
What the article calls a “trapped dipole” is, sadly, using the wrong words. What they describe is a loaded dipole. A 
You would probably want to modify this to align with carefully-spaced links to feed it with ladder line to make a G5RV. It’s not well-designed as-is for a G5RV. But if someone wants to take this as inspiration for a portable G5RV winder, be my guest and report back how it works.