Here I share my process of DIY Inverted V antenna and some insights.

Note, the following generally refers to the shortwave bands, namely radio waves with wavelengths from 80m to 6m. (For the 160m band, honestly use an inverted L or GP… or add inductance if necessary)

Introduction to the Inverted V Antenna

An Inverted V Antenna is a type of antenna similar to a horizontal dipole antenna, but its sides are bent downward, typically forming an angle of 120 degrees or 90 degrees between the dipole legs. Like a dipole antenna, this antenna has two elements connected to the insulated two poles of the signal source. Viewed from the side, this antenna looks like an inverted “V,” hence its name.

(Image source: VU2NSB, 73!)

The Inverted V antenna has several advantages:

  • Requires only one central high support point, making it easy to install, simple and reliable.
  • Being essentially a variant of a horizontal dipole antenna, it also holds advantages in transmission and reception performance.
  • The Inverted V antenna can easily expand bands, and usually, each set of band elements works independently, making internal harmonic interference and common mode currents almost negligible, offering relatively pure background noise and good transmission efficiency with interference resistance.

Despite some downsides, I think that compared to its advantages, they can be overlooked:

  • Since its elements aren’t completely horizontal, the Inverted V antenna doesn’t have a significantly directional radiation pattern… While a typical dipole’s pattern looks like a horizontally placed peanut, the Inverted V’s pattern resembles a horizontally placed egg. This could be a disadvantage in directional scenarios.

(Image source: VU2NSB, 73!)

  • The antenna’s element ends being close to the ground cause ground reflection effects, influencing efficiency. During transmission, poorly insulated element ends can cause electric shock. (Truly a tingling sensation)
  • It cannot achieve seamless and smooth wideband coverage like a log-periodic antenna. (Hey, isn’t that expectation a bit too high?!)

However, however, speaking again, the advantages of the Inverted V antenna are ones that many other antennas lack: simplicity, reliability, multiband capability, low setup requirements, and under such circumstances, it remains a balanced antenna with decent efficiency and reception performance, being relatively versatile, used as a ship or backup military communication antenna. Of course, most frequently used by the penny-pinching HAM community… (If money wasn’t an issue, who wouldn’t go for a Harder, Better, Faster, Stronger antenna 😭)

My Story with the Inverted V Antenna

From starting with a half-wave end-fed to now, I’ve DIYed three generations of Inverted V antennas, each summarizing lessons and optimizing designs aimed at creating: a cost-effective, easy-to-set-up, high-performance, portable Inverted V antenna… (Sounds like an advertisement) Currently, my Inverted V antenna, along with 10 meters of feeder cable, weighs only 1.5 KG, which seems quite heavy, but what if it’s an antenna that can be set up in 10 minutes, almost ignoring terrain, with about 90% transmission efficiency and supports 3 bands (expandable to 5 bands but heavier), with wind resistance over 150 KM/H?

Compared to a GP antenna, it doesn’t require the troublesome radials or difficult-to-secure ground anchors; compared to a portable V antenna, it has a stable triangular structure, eliminating concerns about costly elements breaking in wind and rain; compared to a Yagi antenna… what, you have a portable shortwave Yagi antenna??? Are you crazy? Why not go for a Spiderbeam then? Compared to a dipole, you don’t need to struggle finding a clearing as large as a wavelength or 3 equally high support points…

What more could you ask for?

Having played with amateur radio for just a few years, this antenna helped me achieve DXCC100, served as the World Amateur Radio Day operator, and for the All Asia contest, CQWW, Mulan Weichang DX, and ARRL… countless quiet nights, I sat by the radio, through this antenna, chatting with people thousands, even tens of thousands of kilometers away, listening to their stories, or the warm Morse code… (Why the sudden sentimentality)

After such extensive use and comparison, it turns out that the seniors’ selections weren’t wrong: the portable three giants: GP, Inverted V, end-fed; DX/contest three giants: stacked Yagi, parabolic, GP…

But for beginners, perhaps start with an end-fed… for an advanced step, try the Inverted V antenna.

Now, I will pass on my secret to you!! Now, the time must accelerate!

Design and Selection of the Inverted V Antenna

Theoretical design and practical engineering application differ. In designing the Inverted V antenna, we consider the factors that matter most in practical use, simply put, prioritize the main contradictions. For me, my core needs are: fast setup, stable and reliable, low cost, easy to manufacture. With this design philosophy, engineering design can involve some trade-offs, and of course, under the priority of meeting core needs, other performances should be as high as possible.

Consider the Following Factors

Factors affecting antenna performance:

  • Installation height: The higher, the better, mainly depending on the type of support pole you purchase.
  • Conductivity of the entire system: Alternating signals are sensitive to impedance/SWR.
  • Interference resistance: Common mode currents, parasitic inductance, harmonic interference.
  • Structural stability: Elements should be taut for optimal transmission without wobbling.

Factors impacting setup and portability:

  • Weight and structure: Need to find a balance between the two.
  • Installation method: Any antenna includes wires; distinguishing different band elements/connecting quickly/tensioning/storing without tangling is a skilled task.
  • Carrying and terrain adaptability: Ease of carrying, ability to set up on varied terrains, and the capability to set up under extreme weather or even in the dark!

Factors influencing design, manufacture and maintenance:

  • Manufacturing processes, low cost, structural stability.
  • Ability to quickly find replacement parts, or in critical moments, substituting with available parts.
  • Routine check and maintenance of key parts, easy replacements.

You’ll find, in designing and manufacturing this antenna, it’s much like mimicking the design of a Kalashnikov 47, focusing on adaptability to varied environments and rapid deployment instead of the fixed, stable, and secure location for setting a high-performance antenna. For fixed installations, you could draw from the refined HK-416 rifle’s design philosophy…

And this antenna’s design standards can fully meet the requirements of emergency communication and wartime backup antennas…

Basic Size Design

No antenna can avoid design theories and the equation of speed of light equaling wavelength times frequency… However, starting from basic theories would make this article likely exceed thirty thousand words. Here’s a ready-made antenna design tool: K7MEM/Inverted-V (thanks to K7MEM), where you input the relevant band, height, angle, reduction factor, etc., and it will automatically calculate the parameters for you, allowing a length estimate when purchasing materials.

Note the issue here: the default element angle is 90 degrees, which should be adjusted for the best impedance and SWR, usually from 80 to 120 degrees during actual use. Therefore, during the design phase, something like trailing out the element like a fishhook and then looping back with two cable ties will allow for ease of length adjustment and anchoring.

Material Selection and Manufacture

  • Antenna elements: Best to use single-conductor copper wire, as multi-conductor may produce harmonics. Not too thick, 0.5 mm diameter is enough, ideally 1 mm for added strength. Copper wire should be covered, preferably black anti-oxidation flame-retardant materials, insulated and corrosion-resistant, not prone to aging under strong sunlight. Avoid enameled wire, as it’s prone to short circuits. Alternatively, fine steel wire can be used, although performance may suffer. Always buy extra, for instance, 10m of wire is theoretically needed for a 20m band, but at least 12m should be purchased to allow for trimming and adjustment.

  • Balun (Balance-Unbalance): Used for balanced-unbalanced conversion, impedance matching or eliminating common-mode interference. Some might wonder: if the Inverted V antenna is a balanced antenna, why use a balun? Precisely because: our radios are unbalanced (when not grounded), using a balun can eliminate common-mode interference or force-match the antenna’s impedance to 50 ohms, thus matching the 50-ohm radio impedance. The use of a specific balun type will further determine this… Discussion on baluns is complex, with endless HAM debates, but undoubtedly: with correct design, baluns provide significant efficacy. For my design, a 1:1 current balun was employed primarily to eliminate common mode interference and ensure balance-unbalance conversion. I used a nickel-zinc ferrite NXO-100, which costs about 10 yuan each on Taobao, with magnetic permeability of 100 and temperature coefficient of 400, suitable for shortwaves. The best in class is FT-240-43, but it’s pricey – an option for the affluent. Below are the design schematics of my balun box for reference:

  • Support pole: Borrow the cost-effective gear from fishing enthusiasts, searching for “landing net pole” – either 5-7 meters stainless steel for 30-50 yuan, which is slightly heavy, or carbon fiber for over a hundred yuan, which is light and effective. Real tests show no significant effect on transmission and reception by metal materials. Remember to buy a standard threaded hanger to screw into the pole end for securing the balun at the top. You may also 3D print a dedicated balun casing with fixed clamps for more stable installation.

  • Feeder cable: Simply purchase a standard 50-ohm coaxial cable, specifically 50-3, 50-5, or 50-7, depending on length; the higher the number, the lower the attenuation factor. Generally, 10-15 meters should suffice.

  • Other Fixings: Many details herein: prefer plastic stakes resembling vertical symbols for anchors; metallic ones sometimes lack friction and are heavy. Typically, parachute cord suits as ropes, with Teflon as a posh alternative. For connecting antenna elements with guy ropes, quickdraws (which can serve as insulators) can be bought inexpensively, making setups easy without knots. Also, always buy surplus rope.

  • Electrical Connectors: Considering element replacement and strength, OT open-end copper noses are used for element ends, folding and soldering copper wire into the nose for phenomenal robustness. On the balun side, hex copper screws/nuts and standard UHF coaxial connectors are deployed. Real testing confirms copper’s corrosion resistance in high-salinty and moist environments and its unmatched electrical performance.

  • Other Connective Devices: My balun box is 3D-printed in PLA as I dislike the scent of ABS; Nylon could be used too. On Taobao, buy a waterproof case with pre-drilled holes, or have them do the drilling. My custom casing, with various external suspension points and specific holes/clamps, makes installation easier (and showcases the power of snap-in/snap-out design!). Real tests reveal the PLA’s strength is entirely sufficient. A subtledetail: to achieve a perfect signal-to-noise ratio, my balun box and cover screws are non-metallic nylon, although equally priced, offering a more ~pure~ transmission without metals.

  • A Few More Ideas: I adhered different colored and patterned tapes to band elements for rapid distinction, enabling normal setup even in the dark! Elements, guy ropes, and feeders don’t require dedicated reel devices, as I employ a “zig-zag” winding method, holding a portion of the wire in each hand, retrieving like a cat’s cradle or hand-pulled noodles. Note, it’s zig-zag, not unidirectional winding. This pattern prevents tangling during storage and facilitates rapid deployment next time with a quick shake.

Field Test and Other Insights

Originally, this setup was placed in a simple box, but I later found these components easily fit in a small pouch, ready to grab and go. Now, the ultimate form is a small pouch containing: elements, feeder, balun, support pole, guy ropes, and anchors. That’s all.

Regarding balun winding, despite various techniques, the focus remains on careful and close wrapping, achieving neatness, thus optimizing balun performance like this (although my own wound isn’t perfect), simpler with air-core current baluns for aesthetics. Note, this is only one type of 1:1 current balun!

This balun with 1mm copper elements can stably handle 200W of power continuously.

In actual setups, ideally, elements should be separated by over 30 degrees; if elements are excessive, exceeding 5 sets, parallel element configuration with over 30cm separation may be employed.

Below is an actual setup and test photo, with sustained winds exceeding 150 KM/H that day, gusts over 200 KM/H, and tested truly stable – elements gaining more stability as numbers increase!

I may supplement more insights as they arise…

…73!