The ATU 100 antenna tuner has become a favorite among hams for one simple reason: it delivers a lot of capability for not a lot of money. But out of the box, it’s still a budget tuner. With a handful of smart upgrades, you can turn this little board into a rugged, professional-looking ATU that feels right at home next to higher-end gear.
📌 TL;DR — ATU 100 Upgrades at a Glance
- Problem: Stock ATU 100s use a plastic case, SMA connectors, a tiny screen, and minimal grounding—fine for testing, but not ideal for a serious station.
- Core upgrades: Move everything into a metal enclosure, swap to SO239 connectors, add a 2.4" OLED display, install a metal momentary button, and improve grounding and bonding.
- What you gain: Better RF shielding, stronger and more reliable RF connections, dramatically improved readability, and a tuner that feels like commercial gear.
- Cost vs value: Expect roughly $30–$50 in parts to reach performance and usability similar to tuners in the $150–$200 range.
- Best part: You keep the proven ATU 100 design while adding durability, cleaner RF behavior, and a station centerpiece you can proudly say you modified yourself.
As a ham always tweaking and improving my station, I found that the ATU 100’s basic design was solid—but the case, connectors, and user interface were holding it back. Instead of replacing the tuner, I decided to rebuild it into something I’d be happy to use every day and display in the shack.
In this guide, we’ll walk through five targeted upgrades that dramatically improve performance, RF behavior, and day-to-day usability. Whether you’re a casual operator or chasing DX on multiple bands, these mods can help your ATU 100 feel less like a kit and more like a polished piece of station gear.
Why the Stock ATU 100 Needs Upgrading
The ATU 100 automatic antenna tuner is impressive for the price, but it clearly reflects its “bare-bones” origins. Several stock design choices limit its robustness and long-term reliability in a real-world station environment:
- Inadequate RF shielding - The original plastic case offers almost no RF isolation, so the tuner can both pick up and radiate unwanted RF, which may affect tuning accuracy and nearby equipment.
- Fragile SMA connectors - Lightweight SMA jacks are fine on a bench, but repeated connect/disconnect cycles and full-size coax can stress them to failure.
- Small display - The factory display shows useful information, but it’s hard to read at a glance—especially if the tuner is not right in front of you.
- Basic button quality - The tiny plastic pushbutton feels toy-like and doesn’t match the feel of typical HF radios or other station components.
- Limited durability - With minimal mechanical protection and grounding, the board is more vulnerable to handling damage, static, and RF-related quirks.
After using the ATU 100 regularly, these compromises become more noticeable. Rather than ditching a good design, the better approach is to shore up its weak points—keeping the solid RF core and adding the mechanical, shielding, and usability upgrades it deserves.
Upgrade #1: Enhanced Metal Enclosure for Superior RF Shielding
If you only do one mod, make it this one: moving the ATU 100 into a metal enclosure. A proper case doesn’t just make it look better—it fundamentally changes how the tuner behaves in an RF environment.
Key Benefits of a Metal Enclosure:
- Creates a Faraday cage effect that helps block incoming RF and reduce interference.
- Prevents the tuner and its wiring from acting like unintended radiators near other equipment.
- Adds solid mechanical protection against drops, cable strain, and everyday shack abuse.
- Improves thermal handling by giving heat from components a better path to dissipate.
- Provides a sturdy platform for upgraded connectors, displays, buttons, and grounding.
An aluminum “project box” works very well for this. On AliExpress and similar sites, search for an enclosure around 100mm × 100mm × 50mm to comfortably fit the ATU 100 board, SO239 jacks, and a larger display.
When transplanting the board, mount it using nylon standoffs or insulated hardware so no traces or solder joints can contact the case. That simple step prevents accidental shorts while still allowing you to bond the case solidly to RF ground where it matters.
Upgrade #2: SO239 Connectors for Reliable Connections
The original SMA connectors are one of the tuner’s biggest practical weaknesses. They’re fine for lab-style hookups but not ideal for full-size coax, frequent cable changes, or long-term strain from heavier feedlines. Upgrading to panel-mounted SO239 (UHF) connectors makes the tuner more “real world” friendly.
- Remove the original SMA connectors using a soldering iron and desoldering pump or wick. Take your time to avoid lifting pads or damaging nearby traces.
- Prepare the case by drilling clean, correctly sized holes for the SO239 connectors. A step drill bit works well for creating round, centered openings.
- Mount the SO239 connectors firmly using the supplied nuts and lock washers so they can handle repeated cable connections without shifting.
- Connect to the circuit board with short lengths of 16–18 AWG solid copper wire, keeping leads as short and direct as possible to maintain good RF behavior.
- Establish a solid ground connection between each connector’s metal body and the tuner’s ground plane or case. This bonding is crucial for proper RF return paths.
Once this is done, you can plug standard PL-259 cables directly into the tuner with no fragile adapters in the chain. The mechanical feel alone is a massive upgrade, and you reduce loss points and strain at the same time.
Upgrade #3: 2.4-inch OLED Display for Enhanced Readability
The stock display gets the job done, but it’s not exactly “at a glance” friendly—especially when the tuner is off to the side or you’re operating in a dim room. A larger OLED panel makes SWR and tuning status much easier to read from across the desk.
A popular choice is the HiLetgo 2.42" I2C OLED module. It offers high contrast, wide viewing angles, and a white-on-black layout that remains readable in both bright and low-light conditions. Because it uses I2C, wiring is simple and only requires four connections.
To install the new display:
- Measure and mark the display cutout on the front panel of your new enclosure, allowing for the active area plus any bezel or frame.
- Use a Dremel or similar rotary tool with a cutting wheel to carefully open the window.
- File and smooth the edges, then test-fit the display to ensure it sits straight and centered.
- Wire the display to the ATU 100’s I2C pins (SDA, SCL, VCC, and GND) according to the board’s pinout.
- Secure the display using small screws, brackets, or adhesive standoffs so it doesn’t move when you press nearby controls.
For an even more polished finish, add a thin acrylic window or 3D-printed bezel. This protects the OLED surface from scratches and gives the tuner a “factory-built” look.
Upgrade #4: Premium Aluminum Tuning Button
The tuning button is the one control you interact with the most—yet on many ATU 100 builds, it’s just a tiny plastic switch poking through the case. Swapping it for a high-quality metal momentary button both improves durability and makes the tuner feel more like serious gear.
Look for a small, panel-mount momentary pushbutton with an aluminum or stainless-steel body. The ideal switch has a positive, tactile click without being overly stiff. Choose a finish (brushed, black, or silver) that complements your enclosure and other station gear.
This upgrade might seem cosmetic, but in use it makes a big difference. A solid, confident button press is easier to feel, reduces accidental activation, and contributes a lot to the overall “fit and finish” of the tuner.
Upgrade #5: Improved Grounding for Enhanced Performance
Good grounding is essential for any RF device, and your rebuilt ATU 100 is no exception. Once everything is in a metal case with robust connectors, you have a perfect opportunity to improve RF grounding and bonding throughout the tuner.
- Create a direct, low-impedance connection between the SO239 flanges and the metal enclosure so return currents stay on the case and connectors.
- Add short copper braid or wire straps between the tuner board’s ground plane and the case at multiple points.
- Ensure mounting screws make electrical contact with bare metal by removing paint or anodizing under washers where needed.
- Add a dedicated external ground lug or binding post on the back panel tied to the case so you can easily connect to your station ground system.
Done properly, this reduces RF on the outside of coax, minimizes RF feedback into audio gear, and generally makes tuning behavior more stable—especially at higher power or on lower bands where currents are larger.
The Transformed ATU 100: More Than the Sum of Its Parts
With these five upgrades, the humble ATU 100 stops feeling like a bare circuit board in a plastic shell and starts behaving like a serious, station-worthy antenna tuner. You keep the original’s core strengths—automatic tuning, compact size, and low cost—while dramatically improving shielding, mechanical strength, and usability.
Depending on where you source parts and how fancy you go with enclosures and hardware, you’ll typically spend around $30–$50 on these modifications. Compared to commercial tuners in the $150–$200 range that offer similar cases, connectors, and displays, that’s a very attractive value.
Just as important, you gain the satisfaction of using a piece of gear you’ve personally upgraded. That spirit of homebrewing and experimentation is at the heart of amateur radio—and every time you hit the tune button and watch that OLED display drop the SWR, you’ll know exactly what’s happening inside the box you rebuilt.
Ready to Build Your Own ATU 100 Tuner?
Take your radio setup to the next level with the ATU 100 Tuner—a DIY project that’s perfect for tuning your antenna like a pro. Affordable, customizable, and loved by hams everywhere, it’s time to get your hands on one and start building!
Shop ATU 100 Tuner Now