From Box to Band: Assembling the QRP Labs QMX in Bangladesh

The Genius of Hans Summers and QRP Labs

When you talk about homebrew amateur radio in the modern era, it is absolutely impossible not to mention Hans Summers (G0UPL). Hans has achieved legendary status in the ham radio community for a very specific reason: he designs kits that democratize high-performance radio. QRP Labs is not about slapping a few basic components together for a subpar, noisy experience; it is about elegant, cutting-edge RF engineering made accessible and affordable to the everyday operator.

The QMX (QRP Labs Multimode Transceiver) is a prime example of this design philosophy. It is a true SDR (Software Defined Radio) packed into a footprint barely larger than a deck of cards. Capable of CW, single sideband (SSB), and digital modes like FT8 right out of the box, it is nothing short of a technological marvel. I specifically opted for the Rev 4 High Band version, which covers 20M, 17M, 15M, 12M and 10M. This band spread perfectly complements the frequencies I designed my multiband Moxon antenna for. The idea of pairing a homebrew antenna with a homebrew radio was a dream I was determined to realize.

If you have been following my amateur radio journey here on the blog, you know that my fascination with high-frequency (HF) operation is driven by a profound desire to build, experiment, and push the boundaries of what is possible with limited resources. After the incredible and eye-opening experience of the S21DX IOTA DXpedition in 2024, my entire perspective on what makes a truly great station fundamentally changed. I came back to Dhaka with a burning desire to minimize my setup and focus on efficiency over brute force.

That drive led to the creation of my custom multiband Moxon antenna—a project made possible by the generous rooftop space of my good friend S21RED. But a great, highly directional antenna is only half of the equation. To truly embrace the spirit of portable and minimalist operating, I needed a transceiver that matched that ethos. I wanted something lightweight, highly capable, and most importantly, something I could build myself entirely.

The Arrival and First Impressions

The anticipation of waiting for specialized radio gear to clear customs is a universal ham radio experience, and receiving this kit here in Bangladesh was no different. Seeing the padded shipping envelope arrive, complete with its international routing stickers from its long journey, felt like the official starting gun for this project. Inside that unassuming package were all the components required to build a world-class transceiver.

Unpacking a QRP Labs kit is an exercise in extreme organization. The printed circuit board (PCB) is beautifully manufactured, and the bags of tiny components—resistors, capacitors, microcontrollers, and the infamous toroids—can look incredibly daunting to the uninitiated. But as I wrote in my recent guide on choosing your first HF antenna, amateur radio doesn't have to feel like rocket science. It just requires patience, a systematic approach to reading instructions, and a willingness to learn from your mistakes.

The Assembly Process: Soldering and Toroids

Building the QMX is not a quick weekend project you rush through in a single afternoon; it is a meticulous journey. The Rev 4 board is densely packed with surface-mount and through-hole components, demanding a fine-tipped soldering iron, good lighting, and a very steady hand.

The most infamous part of any QRP Labs build is, without a doubt, winding the toroids. For many first-time builders, these inductors are the most intimidating part of the process. You have to carefully count the exact number of turns of enameled copper wire, ensure they are tightly and evenly wound against the ferrite core, and properly scrape the tough enamel off the tips before attempting to solder them to the board.

You can see the RF deck really taking shape. The tightly clustered, golden-copper toroids dominate the upper half of the board, sitting alongside the relays and power components. Winding these perfectly is absolutely crucial for the radio's low-pass filters and the overall efficiency of the power amplifier. I took my time here. Every time I completed one and soldered it into place, I felt a deeper connection to the underlying physics of RF engineering.

Once the main board components were seated and soldered, the next critical phase involved marrying the user interface to the radio. Snipping the excess header pins and mounting the LCD screen requires absolute precision . You can see the bare display mounted to the front PCB, just before the final enclosure brings it all together.

Fitting the finished boards into the sleek black aluminum case transforms it from a messy workbench project into a professional-grade piece of equipment. The iconic green backlight of the QMX display shines brightly through the customized front panel, flanked by the tactile menu buttons and rotary encoders. Securing the final metallic knobs onto the VFO and tuning shafts was a deeply satisfying moment. At last, the radio was physically complete.

Regulatory Compliance: Informing the BTRC

Before taking the newly minted radio on the air, there was one vital administrative step that could not be skipped. Operating responsibly is a core pillar of amateur radio, especially here in Bangladesh where our community is growing. Because the QMX is a kit built from individual components rather than a standard, type-accepted commercial off-the-shelf (COTS) radio from a major manufacturer like Icom or Yaesu, it falls into a slightly unique category.

To ensure full transparency and strict compliance with our local licensing frameworks, I formally informed the Bangladesh Telecommunication Regulatory Commission (BTRC) about this homebrew build. I provided them with the detailed technical specifications of the Rev 4 High Band QMX, clearly detailing its QRP power output, operating frequencies, and emission types. Keeping the regulators in the loop is essential for homebrewers. It not only ensures that your specific station is fully legal to operate, but it also helps maintain the strong, positive, and cooperative relationship the amateur radio community has with the telecommunications authorities in Bangladesh. It demonstrates that as operators, we are technically competent and strictly adhere to both international and local radio regulations.

Taking It Outside: The Field Test and Wild Ambitions

A radio this small and efficient is practically begging to be taken outdoors. While my Moxon antenna at S21RED's QTH is fantastic for fixed operations, I wanted to test the true portable capabilities of the QMX out in the open air.

I packed up the transceiver, a compact lithium battery pack, a portable blue Bluetooth speaker (wired via auxiliary for audio output), and my heavy-duty green CW paddle. I set up on a concrete ledge outside, surrounded by nature—a far cry from the electrically noisy, interference-heavy environment of a typical Dhaka apartment building.

The complete portable setup is a beautiful testament to minimalist operation. The entire station fits effortlessly into a small backpack. I connected a simple wire antenna, plugged in the battery power, and held my breath as I flipped the switch.

The moment the screen booted up, displaying the VFO at exactly 14.200 MHz , a massive wave of relief and pride washed over me. It worked perfectly. The green display was crisp, and more importantly, the receiver was completely alive. In the accompanying video clip, you can hear the sharp, distinct tones of CW signals cutting right through the background noise, pouring out of the external speaker.

To sit next to the QMX, hand resting on the green paddle, and realize that the very signals you are hearing are passing through filters, mixers, and amplifiers that you wound and soldered yourself is an indescribable feeling.

The Journey Continues: Riversides and Radio Waves

Building the QRP Labs QMX has been one of the most rewarding technical projects I have undertaken since earning my S21FIA callsign. It taught me patience, vastly improved my soldering skills, and gave me a profound appreciation for the brilliant circuit design of Hans Summers.

But this bench test is just the beginning. My ultimate desire is to pack this tiny rig, a small portable battery, and a super lightweight wire antenna into a daypack and head out into the wild. I picture sitting quietly by a remote riverbank here in Bangladesh, far away from the city's electrical noise, with nothing but the sound of the flowing water and the rhythmic tone of Morse code in my ears. Casting a line out—not for fish, but for HF signals bouncing across the ionosphere—and playing with radio waves in the middle of nature is exactly what this hobby is all about.

If you have ever considered building your own transceiver, I cannot recommend the QRP Labs kits highly enough. Don't let the toroids or the dense circuit boards intimidate you. Take your time, enjoy the careful process, and before you know it, you will be making contacts around the world on a radio born on your own workbench.

As always, this blog is not just a personal logbook—it is a collaborative place for us to exchange ideas. Have you built a QRP kit recently? What is your favorite portable antenna to pair with a lightweight rig like the QMX? Drop a comment below, or send me an email.

Together, let's keep experimenting, keep learning, and keep the airwaves alive with our voices and signals.

73 de S21FIA!

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