Tag Archives: QRP Labs QMX

Field Reports, Morse Code, News, Portable, QRP, Videos

Testing New POTA Gear: High-Band QMX, Explorer Carbon Fiber Mast, Pressure Paddle, and a Packed Nemo Resolve 25L

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Please note that this POTA (Parks On The Air) activation took place on September 19, 2024—eight days before Hurricane Helene devastated western North Carolina. This is one of a few field reports and activation videos I’ll be sharing that took place before Helene’s arrival.

As I mentioned in my last field report, I haven’t been back to the Vance State Historic Site since the storm, as it’s been closed. Located in the Reems Creek valley, the site likely experienced extensive flooding. I hope this park can recover and reopen soon.

I hope you enjoy this field report and activation video. I’ve thoroughly enjoyed reliving it while preparing this for you.

Thank you!
Thomas (K4SWL)

On Thursday, September 19, 2024, I made time for a POTA activation at the Zebulon Vance Birthplace (US-6856) and brought along a few new items to make it even more interesting.

New Pack

I packed my new gear along with extra equipment to fill out my new Nemo Resolve 25L backpack (check it out in gear links below). I wanted to see how well it could handle a full load and how comfortable it would be to carry.

Turns out, it’s very comfortable, and I could easily fit more in this pack than I’d likely ever need. It’s a keeper.

New QMX

First, I brought along a new QRP Labs QMX transceiver. If you’ve been a long-time reader, you’ll know I’ve had a QMX for about a year and think it’s a brilliant little radio. This one, however, is the “high band” version, meaning it covers 20-10 meters. My other QMX is the “low band” version, covering 80-20 meters.

As soon as the high band QMX was announced by QRP Labs, I grabbed one. I purchased an assembled version, knowing it could be a year (or much longer) before I’d have time to actually build one.

When I received this new QMX—I’m not sure, months ago?—I tucked it away in a drawer while reorganizing my shack, then promptly forgot about it (in my defense, I had a crazy year). I eventually rediscovered it, and here we are!

I’d been looking forward to taking it to the field.

New Carbon Fiber Mast

At Hamvention this year (2024), I ran into my good friend Mike Roberge (KE8PTX). He told me he was super excited about a new product that had been showcased—not a flagship radio or similar, but the Explorer POTA20Carbon Fiber Mast. 

Mike was one of the very few people who actually purchased one at Hamvention to take home. I believe Gigaparts only had two or three on hand—mainly for demo—so everyone else had to place an order and wait 6-8 weeks for the first shipment.

Meanwhile, Mike, being the clever fellow he is, designed a 3D-printed ground spike holder that fits a tent stake. This allows the user to unscrew the base cap of the Explorer mast, insert Mike’s ground spike, and support the mast without needing guy wires, etc.

If this sounds familiar, it’s because Mike made a video about how easy it is to deploy the Explorer mast with his ground spike.

I purchased my Explorer pole via Gigapart’s online store during or right after Hamvention. I didn’t receive my mast until sometime in August. This activation was the first time I tried it out in the field.

I deployed my 20M EFHW (built on a TennTennas transformer) by attaching one end to the tip of the Explorer pole, then sloping it down so the feedpoint was close to the edge of the picnic shelter at Vance.

K3ES’s Grippy Pressure Paddle

Another item I rediscovered in September was a VK3IL pressure paddle my good friend Brian (K3ES) gave me at Four Days in May during Hamvention. His version is a standard VK3IL pressure paddle, but with some padded material under the heat shrink, making it easier for big hands to grip.

Brian’s paddle paired nicely with the QMX!

With everything set up, it was time to hit the air.

Gear:

Note: All Amazon, CW Morse, ABR, Chelegance, eBay, and Radioddity links are affiliate links that support QRPer.com at no cost to you.

Radio

Antenna, Support & Cable Assembly

Packs & Cases

Speakers & Headphones

Logging Supplies

Key and Key Accessories

Battery

Camera/Audio Gear

On The Air

The QMX, of course, performed well during this activation.

I did encounter some difficulties at the beginning when the QMX produced significant audio pops in the CW sidetone audio whenever I keyed the radio. I spent a few minutes troubleshooting and even changed speakers, thinking it might have been an issue with the Soundcore Mini.

It turned out to be related to toggling the AGC function. I eventually managed to resolve the audio pops and used the Soundcore Mini. I’m not sure I could replicate the process exactly, but I got it working. (If you’ve had a similar experience, I’d love your input.)

Otherwise, the activation went very smoothly.

I worked my first ten stations in eight minutes—woot!

Activity slowed down a bit after the first ten, but I still managed to work 17 stations in under half an hour.

Many thanks to everyone who hunted me!

QSO Map

Here’s what this five-watt activation looked like when plotted out on a QSO Map:

Screenshot

Activation Video

Here’s my real-time, real-life video of the entire activation.  As with all of my videos, I don’t edit out any parts of the on-air activation time. In addition, I have monetization turned off on YouTube, although that doesn’t stop them from inserting ads before and after my videos.

Note that Patreon supporters can watch and even download this video 100% ad-free through Vimeo on my Patreon page:

Click here to view on YouTube.

Explorer Carbon Fiber Mast

I love that the Explorer mast fits easily in my Nemo backpack. I see myself using it a lot for SOTA and POTA activations where suspending an antenna in a tree isn’t possible.

It’s super lightweight and compact, and Mike’s ingenious tent stake spike mod makes this mast so easy to deploy.

I also enjoyed using Brian’s pressure paddle during this activation—thank you, OM! It’s comfortable to grip and use.

This high-band QMX will make a brilliant SOTA transceiver. I need to take advantage of these high bands while the ionosphere supports them this solar cycle!

Thank you

Thank you for joining me during this activation!
I hope you enjoyed the field report and my activation video as much as I enjoyed creating them!

Also, thank you for all of your recent support and kind messages following Hurricane Helene.

Of course, I’d also like to send a special thanks to those of you who have been supporting the site and channel through Patreon, and the Coffee Fund. While not a requirement, as my content will always be free, I really appreciate the support.

Thanks for spending part of your day with me!

Cheers & 72,
Thomas (K4SWL)

Digital Modes, Field Reports, FT4, FT8, Guest Posts, How To, News, Portable, POTA, QRP

Karl Heinz’s Pocket-Sized Digital HF Station

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Many thanks to Karl (K5KHK) for sharing this guest post, which originally appeared on his blog, Karl Heinz Kremer’s Ramblings:

A Digital Station in Your Pocket

by Karl Heinz (K5KHK)

How small can a complete station to work FT4/8 be? With the QRP-Labs QMX, we have a transceiver that certainly fits the bill for a small station. By itself it can only be used for CW, to use the digital modes, one has to combine it with a computer. Even the smallest laptop is too big the fit into the pockets of my cargo pants – we are trying a pocket sized station after all 😉

In this article, I will describe how to use a QMX transceiver and an iPhone to activate a POTA park with FT8.

The Components

My QMX is the original that was released at FDIM 2023, so it covers 80m to 20m. Mine is serial number #20.

My iPhone is small enough, but unlike Android based phones, the QMX cannot be connected directly to the phone. Apple sells a “camera adapter”, which plugs into the phones Lightning port on one side and provides a USB connection on the other end. $29 for the original Apple part was a bit hard to swallow, so I opted for something cheaper straight from China’s “we clone everything” factories: https://amzn.to/3WDSfUc

[Please note: All Amazon links are affiliate that support QRPer.com.]

 

The picture shows both a USB and a lightning port on the adapter. This should allow the phone to be powered/charged while the adapter is being used – more about that later.

Another limitation is the antenna: The QMX does not have a built-in antenna tuner, and even my QRP sized ZM-2 would have to live in a different pocket 🙂 My plan is to use a resonant antenna so that I would not need a tuner.

The easiest antenna with a good match is a dipole, but that is a bit more challenging to deploy in the field, so I opted for an end-fed halfway (or EFHW) antenna with a 49:1 transformer. I 3D printed a winder that allowed a BNC connector and the transformer to be mounted on the wire winder:

The design came from Thingiverse: https://www.thingiverse.com/thing:2871679

Because I am using a different toroid for the transformer, I had to remove the “bump” that is holding the toroid in place. Going forward, I may change the design a bit more to have so that I can fit more wire on the winder.

For those familiar with the transformers usually used for EFHW antennas, the picture shows two things that are different: As I’ve already mentioned, I am using a different toroid (the Fair-Rite 2661102002 core, which is a type 61), and a different winding pattern. More about that in a future post.

To power my station, I am using a TalentCell rechargeable 12V power bank:  https://amzn.to/3snTyr8

First Test

With everything in place, I tried to make a quick FT8 contact from home with this setup, but with my “big” EFHW antenna in my backyard. Because it was just a quick test, I did not even bother to hook up the charging cable for my phone (more on that later).

The software I am using is iFTx, which supports both FT4 and FT8.

I connected the phone to the adapter from above, connected the adapter via a USB cable to the QMX, and connected the QMX to a 12V power supply (unlike anywhere else in ham radio, 12V here means 12.0V and not the usual 13.8V), and hooked up the antenna to an antenna tuner and then to the EFHW in my back yard.

I answered an FT8 CQ call and successfully completed the FT8 exchange. The software does the automatic sequencing of the different messages, so it is very straight forward to use. With this first contact, I verified that the iPhone/adapter/QMX setup does work.

The Real Test

The next attempt was while camping at Hamlin Beach State Park (US-2068). I set up everything just like at home, but because I was planning on being on the air for a while. I also hooked up the cable to charge my phone while I was operating.

I was able to receive stations, but could not transmit. What made the troubleshooting more complex is that during setup, I created some sparks (that is why I do not like the barrel connector for power). I was pretty sure that the QMX was not involved, but not being able to transmit kind of suggested that I killed the finals. So I put everything away and used my KX2 instead.

Back home, I did some troubleshooting and hooked up a straight key to the QMX and it worked: I was able to finish a few CW QSOS without a problem, so the finals were definitely OK. I then set up the system again for FT8, and sure enough, I was able to make a contact. Because it was a quick test, I did not bother to use the power cable for the phone. By now, most of you probably know what the culprit was, but because I did not spell things out like this, I was still in the dark.

Success At Last

Fast forward a few more days… We went back to Hamlin Beach State Park – but this time to the picnic area – and I set up my station again. And sure enough, once everything was set up, the QMX did not transmit. This is when I took a step back and reviewed everything I had done so far, and slowly I came to the realization that when I provide power through the adapter to the phone, the QMX would not transmit.

I was able to finish my FT8 activation with my pocket sized digital station. I did run into one problem however: iFTx allows to automatically determine one’s grid square – which of course is important for FT8. When I enabled that, it correctly put me into FT13 at first, but a few QSOs later it switched me to JJ00aa – I reported this as a bug to the developer.

Using iFTx with the iPhone

The connection from the phone to the QMX is audio only. iOS does not allow an application to open a serial port connection (unlike Android). This means that the QMX will not receive any frequency information from the phone, and also no PTT signal. For this setup to work, the operator has to make sure that the QMX is tuned to the correct frequency that the correct band is selected in iFTx, and that the QMX is set to VOX mode (this is in the Digi Interface menu).

When configuring iFTx, it is possible to select a “Special Interest Activity” like POTA. This is then added to the CQ call as in “CQ POTA K5KHK FN13”.

As I’ve mentioned before, the application will automatically sequence the correct messages when a station answers the call.
Once the QSO is completed, it will be logged to the iFTx internal log, which can be exported via the usual “send to” methods available in iOS (e.g. email the log, save as a file, …).

When exporting the log, there is a choice of exporting everything, or only the new QSOs since the last export. This will create an ADIF file, which can be submitted to the POTA program, or imported into any other logging program.

At the end, I was successful in building a “pocket sized” digital station based on the QMX, I just need a fully charged phone and cannot depend on charging it while operating.

Click here to check out more articles from Karl on his blog!

Field Reports, Guest Posts, Morse Code, Portable, POTA, QRP, Travel

UK POTA Rain and Shine

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by Matt (W6CSN)

Bletchley Park

Most readers of this blog are probably familiar with Bletchley Park and the significance of this place in breaking the codes used by the axis military forces during the second world war.

The electromechanical systems developed and used here to aid the codebreakers in their daily work led directly to the electronic digital computers of the mid-twentieth century, and then to the modern world as we know it.

After boarding the London Northwestern Railway at Euston station, the hour long train journey took us from central London, through the suburbs, then the pastoral English countryside to the station at Bletchley, just south of Milton Keynes.

Bletchley Park is a five minute walk from the train station at Bletchley, the town of the same name. In keeping with the formerly clandestine nature of the work at Bletchley Park, there are no loud signs to welcome you, just the Union Jack flying over the nondescript visitor center in Block C.

Exiting the visitor center, any ham will quickly spot the three-element SteppIR Yagi perched atop a roof-mounted tower. Also from the tower, a folded dipole extends over the the Block B building which houses the Alan Turing museum exhibits. The other end of this antenna farm is plugged into GB3RS, the amateur radio station for the National Radio Centre of the RSGB.

The friendly and helpful staff of amateurs at the NRC played a crucial role in my hoped-for plan of activating Bletchley Park for Parks On The Air.

Surprisingly, the POTA page for GB-0507 showed only a handful of activations of this iconic location. Seeing as this is a heritage site, I sent an email to the NRC about week before my visit asking for advice on how to be a welcome guest POTA operator.

Note, the NRC is colocated on the grounds of the museum but they are not a part of Bletchley Park. The NRC is a separate organization.

Martyn G0GMB, the Director of the NRC, kindly responded to my enquiry and informed me that individual amateur radio activity is not generally permitted on the grounds of Bletchley Park due to the number of visitors they receive and concerns about RF safety. This could explain the low number of activations.

The sharp eyed will spot the GB3RS beam across the pond.

Martyn suggested I could set up in the overflow car park few minutes walk down the road from the visitor center. While not on the grounds of Bletchley Park proper, the parking lot operation would still be in the spirit of POTA and would reasonably count as a valid activation location.

When I arrived at Bletchley Park on Friday afternoon, I was met by Mervyn G4KLE who was expecting me thanks to a note left by OM G0GMB. Mervyn asked where all my equipment was and I motioned to the pack on my back.

Because my radio and antenna was a low impact, minimal footprint QRP setup, I was told that I could make use of the picnic table just out the side door of the GB3RS shack, with my antenna setup just beside it. This dead-end spot was not on any of the paths frequented by park visitors and my antenna would not be easily visible.

The antenna is low profile

This was a much better arrangement than trying to activate from a car park without a car! I quickly deployed a GRA-GNT micro tripod with center spike pushed easily into the soft ground. The GRA-7350T loaded vertical and a set of short radials provided an SWR of 1.05 to 1.

I chose the QMX as a travel radio while in Britain because with it, the overall kit is very lightweight and compact. With the exception of the tripod the whole kit fits in my carry-on. The GRA-GNT antenna mounting kit has to fly in checked baggage due to several aggressive looking spikes that would certainly be flagged by airport security. Continue reading UK POTA Rain and Shine →

Accessories, Articles, Guest Posts, Morse Code, News, Portable, POTA, QRP, QRPers, Skills, SOTA

Guest Post: Preparing radio and trail gear for a once-in-a-lifetime, epic through-hike

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We’re excited to welcome Bryce Bookwalter (KD9YEY) as a guest contributor on QRPer.com!

I had the pleasure of meeting Bryce at the 2024 Hamvention, where he shared his plans for an ambitious hiking adventure next year. Knowing he wanted to incorporate radio into his journey, I asked if he’d be willing to bring us along by sharing updates on his preparations and experiences on the trail.

To help fund his adventure, Bryce has started a GoFundMe campaign, which you can learn more about at the end of this post. Additionally, please note that some of the gear links below are affiliate links that help support QRPer.com at no extra cost to you.

Bryce, take it away…

Backpacking Booky: A Quest to Hike the Appalachian Trail

by Bryce (KD9YEY)

The dream is formed, and it always seems so attainable. It’s as easy as the desire to walk in the woods and explore the beauty of nature. To find community with the world around you and discover your reflection is no different than the hills and streams that stand steadfast against time. I feel like anyone who wishes to pursue a long hike starts with these feelings and lofty ideas of what the trail will be like and the experience they will have…and then you realize you’re going to have to poop out there.

Hello, my name is Bryce Bookwalter and in 2025 I am attempting a thru-hike of the Appalachian Trail. This has been a goal of mine since I was in my freshman year of high school in 2005 and first learned about the trail.

I was in Front Royal Virginia at the time and one weekend we went hiking and our trail passed by the A.T. I remember hearing that this same trail traveled all the way from Georgia to Maine and it blew my mind.

I wanted to hike it right then, and I still want to hike it today. Life happens of course, and I had to let the dream go for some time. I have found myself in a unique time of my life recently where I will be between schooling and a new job and I realized that if I don’t hike the trail now, I may never get the opportunity again. My education has been off and on throughout the last decade and 5 years ago I ran out of my GI Bill that I received from the Army. With only 2 semesters remaining until I received my degree, I started doing construction to save money to return to school. 5 years later I have returned to Indiana University, and I am now 1 semester away from finally receiving my degree in Community Health. With this milestone accomplished, I have decided that before I start another job I need to try and complete my long-time goal of hiking the A.T.

It is an interesting turn of events that brought me back to the love of backpacking. It would seem an illogical path to say that Ham Radio is responsible for my rekindled passion for the outdoors, but this is in fact the case. Two years ago, my stepdad Joe (W9NVY) got into Ham Radio, and I decided to at least get my Technician License so that we can communicate through the local repeaters. Later that year we both participated in the GOTA team for a local Field Day club out of Indianapolis. After working to set up the antennas and operate for 24 hours, I was hooked on HF!

Since then, I have received my General License and am currently working on my extra. I learned about Parks on the Air and discovered that there is a whole side to this hobby that involves preparing gear, packing it, and carrying it into the wild to set up and operate remotely. This speaks to me in so many ways. Not only do I get to play radio, which I love, but I also get to add hiking and backpacking to the mix.

I am a gear junkie! I will admit it openly. I love researching gear and seeing what works for others and obtaining gear and putting it to the test in the field. This harkens back to some of my favorite aspects of the military and Civil Air Patrol before that.

Civil Air Patrol days.

So, let’s talk gear! When preparing for a thru-hike, there is a lot to consider. You’re not just planning for a weekend outing but for a 4–6 month long adventure. It’s hard to know what to take…and even harder to know what NOT to take. There is a saying that I agree with that says, “Backpacking is the art of knowing what NOT to take.” This is so true.

There are different levels of backpackers, from conventional to ultralight.

Conventional backpackers can find their packs weighing 30-40 lbs. or more. Ultralight typically have their base weight (weight without food and water) down to under 10 lbs. I find myself somewhere in the middle. I lean towards lightweight, but I certainly do not consider myself an ultralight backpacker. Especially considering I will be carrying radio equipment with me along the trail.

The journey of finding the right gear is a constant process, though I believe I have narrowed the list down considerably. So, I will break my gear down into two sections: Backpacking Gear and Radio Gear. Continue reading Guest Post: Preparing radio and trail gear for a once-in-a-lifetime, epic through-hike →

Field Reports, News, Portable, POTA, QRP

Change Is Good

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by Matt (W6CSN)

Recently, OM Witherspoon (K4SWL) wrote a blog here and shared a POTA activation video in which he described the benefit of changing up your operating location within a large park to keep things fresh or simply to be able to activate within a given schedule.

Activation zone looking over the Pacific

That got me to thinking about my own “home” park, Presidio of San Francisco US-7889, a large park which is also part of an even larger reference, Golden Gate National Recreation Area (GGNRA) US-0647. Recently my XYL, who is very patient, has been subjected to my complaining about being bored by doing the same activation over and over.

Classic vistas from the Presidio of SF

My typical POTA outing is after work, I drive ten minutes down to the East Beach parking area, set up a base-loaded vertical on the roof of my car and plug in the trusty FT-818. Mind you, this is not a bad setup. The location combined with repeatable antenna installation reliably produces contacts and I usually have a complete activation in about 30 minutes.

GRA-7350T antenna deployed

The XYL’s suggestion was, “hey, why not play radio somewhere else?” and K4SWL’s blog and video were an inspiration as well. So I left the FT-818 in the shack, packed up a QMX kit, and headed for the high bluffs in the Presidio that overlook the Pacific Ocean to the west. I setup on an out of the way granite bench that was part of a World War II memorial to servicemen who perished in the coastal waters of the Pacific.

World War Two commemorative wall

My plan was to get on 15 meters in the hope of catching some early JA’s or other Pacific rim DX. The vertical antenna deployed easily and though the location was substantially protected from the strong wind gusts, I did stake the tripod down with a pair of tent pegs.

Tent pegs keep the tripod secure

With an SWR of below 2:1 on 21 MHz I set to calling CQ and posted a spot on pota.app advertising that I was in US-0647 GGNRA, even though I was also still in US-7889. Turns out 15 meters was dead, for me at least. Not a single nibble after 15 minutes of calling.

Good SWR on 15 meters

After a QSY to 20 meters, another half hour brought in only four QSOs! This location and radio combo was certainly a nice break from the usual and even though the QSO pace was glacial, it was quite satisfying and refreshing to do something different.

The QMX station ready for action

Since the clock read just after 00 UTC there was plenty of opportunity to gather the needed contacts for a complete activation. If necessary I could even come out the next day before 23:59 UTC. But since I had no particular time constraint for the evening, I decamped for East Beach where I was pretty sure I could wrap up the activation in short order.

Sunset over SF Bay

Even though I was back at my “usual” spot, starting the activation somewhere else was the change I needed to break the routine. Six more QSOs validated the activation in a matter of minutes. I swear being down close to the waters of San Francisco Bay adds at least 3db to my signal. There is a reason I frequent this particular spot.

Sun going down behind the Golden Gate

I feel fortunate to have so many locations within US-0647 and US-7889 that are quite close to home. I plan to take advantage of this diversity of operating spots, knowing that the “East Beach Amplifier” is always available if my QRP is not cutting it.

72 de W6CSN Matt

P.S. I did, in fact, log this activation as a two’fer.

Field Reports, Morse Code, News, Portable, POTA, QRP, QRP Radios, Videos

Woo hoo! Finally taking my QRP Labs QMX on a POTA activation!

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Those of you who purchased a fully-assembled and tested version of the QRP Labs QMX are, no doubt, patient people.

While you can order a kit version of the QMX and receive it fairly quickly (still, I believe), the assembled versions take more time as the QRP Labs crew is small and they build and test these by hand.

I ordered mine on June 5, 2023, and it shipped on December 27, 2023.

Truth is, I’ve had a QMX kit since Hans Summers announced it at Four Days In May (FDIM) prior to the 2023 Hamvention. I’ve been meaning to build it but, as many of you know, my life has been a tad crazy these past months and I never got around to it.

I purchased an assembled version of the QMX because I will be reviewing this one and wanted a factory-tested unit. I would have never guessed I’d receive the assembled unit before building it!

Familiar Form-Factor

The QMX looks so much like my QCX-Minis, I’ve gotten them mixed up in the shack! The menu system is very similar to the QCX, but there are some changes to accommodate band changes, modes, etc., as the QCX-Minin series is mono-band CW only.

The QMX, on the other hand, is a five-band, five-watt, multi-mode (CW, Digital, and likely SSB in the future) transceiver. It’s hard to believe you can purchase the QMX for as little as $90 (bare-bones) kit or $165 (fully-assembled and tested).

I initially thought I had an issue with my QMX because it kept shutting down the transmit function. Turns out, that was all user-error. I mentioned the issue on an episode of the Ham Radio Workbench podcast, and a couple of listeners wrote to tell me what I was doing wrong: I was feeding it too much voltage. The QMX doesn’t want more than 12V or so. If the radio detects even a temporary mismatch, it shuts down the TX to protect the finals, etc.

I was unintentionally triggering the QMX’s self-protection functionality!

Once I figured that out, I decided to simply pair my QMX with my Bioenno 3Ah 9V LiFePO4 battery. That would yield about 3 watts of output power and be a comfortable voltage for the QMX.

Vance Historic Birthplace (US-6856)

On Thursday, March 7, 2024, I finally took the QMX outdoors where it belongs! I had a one-hour window of time to complete a full activation. I decided to pair the QMX with my Chelegance MC-750 vertical.

My QMX is a “low-band” version that covers 80, 60, 40, 30, and 20 meters. I thought the top end of its band coverage would serve me best mid-day, so I planned my activation around 20 meters.

Setup was easy and simple. You can see the full set-up process in my activation video below.

Gear:

Note: All Amazon, CW Morse, ABR, Chelegance, eBay, and Radioddity links are affiliate links that support QRPer.com at no cost to you.

On The Air

I hopped on the air and started calling CQ POTA after sorting out my QMX settings–I needed to adjust the sidetone and I had to take it out of split mode! Continue reading Woo hoo! Finally taking my QRP Labs QMX on a POTA activation! →

Articles, Field Reports, Guest Posts, How To, Kits, News, Portable, POTA, QRP, QRP Radios, Reviews

QMX – From Kit to Field!

16 Comments

by Matt (W6CSN)

The Radio

The QMX by QRP Labs is a five band, multi-mode radio introduced by Hans Summers G0UPL at FDIM in 2023. The QMX is the next logical step in the radio development journey at QRP Labs, bringing together the innovative approach to FSK modes like FT8 from the QDX and the CW performance of the QCX series. This is all done in same enclosure as the QCX-Mini which is not much larger than a deck of playing cards.

Size of the QMX compared to standard deck of playing cards.
The QMX is about the size of a deck of cards.

The keen observer will notice that the QMX also sports a built-in microphone which, along with associated circuitry, supports future introduction of voice modes by way of firmware update. Other notable features include SWR metering with protection as well as solid-state “PIN” diode T/R switching, plus the option for “high band” coverage of 20 through 10 meters in addition to the original 80m-20m version.

Most hams have, at one point or other, forgotten to throw the antenna switch, adjust the tuner, or even connect an antenna before transmitting. The SWR meter and protection really sets the QMX apart from earlier QRP Labs radios. There are plenty of sad tales on the QRP-Labs forums from QCX or QDX users that “smoked” the BS170 mosfet finals in a moment of operating into a badly mismatched load. It’s remarkably easy to do, ask me how I know!

The Build

Based on experience with the QCX-Mini and having put together several QDX’s, I admit to being hesitant to starting assembly of this radio. The level of integration in the QMX as a multi-band, multi-mode unit is probably the highest yet to come out of QRP Labs. The components that were merely small in earlier radios are absolutely tiny in the QMX, specifically the LPF toroidal cores. The main board, internal switching power supplies, display, and controls board are all sandwiched together in a tight fit for the custom enclosure.

photo showing a partially completed circuit board
Most of the electronic components installed on the main board.

The build started with a slow and methodical approach of doing a little bit each day and working in the morning when my mind was fresh and there was good light on my workbench, a.k.a. the dining room table.

The first “disaster” happened when performing the factory recommended modification to Revision 2 boards shipped in 2023. The mod calls for a protection diode to be installed across a SMD mosfet. Several leaded 1N4148 diodes were available in my “junque” box so I attempted to carefully fit one of these in the right position on the board. While soldering the diode in place I managed to lift C508, a microscopic .1uF SMD capacitor, clean off the board!

photo of circuit board with modifications
The suggested modification adding a protection diode.

Given the tools at my disposal, there was no way I was going to be able to get that capacitor back into place. Therefore, I grabbed a standard through hole .1uF cap and painstakingly got it connected in the right place, verified by lots of continuity testing.

Once finished with all the electronic components on the main board, I was feeling pretty cocky and also the completion of the project was more clearly in view. The cautious and methodical approach gave way to a faster build pace, which directly lead to the second “disaster.” While installing the headers that connect the main board to the display board, I failed to CAREFULLY READ THE ASSEMBLY MANUAL and soldered the male pin headers where I should have installed the female sockets!

This misstep might have ended the project right then and there if I had not at some point in the last year bought a proper desoldering tool. This is not an expensive automatic vacuum pump powered solder re-work stations, but rather a heating tip and manually actuated solder sucker built into one tool. Twenty-two unsoldered connections later, we were back on track. Continue reading QMX – From Kit to Field! →

Field Reports, Guest Posts, News, Portable, POTA, QRP, Travel

POTA Field Report: Andrea Activates Two Iconic Cold War Sites

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Many thanks to Andrea (IW0HK) who shares the following field report:

Cold War POTA in Berlin

by Andrea (IW0HK)

In the last week of October, I found myself in Berlin for a work commitment.

Taking advantage of two half-days off, I wanted to combine two of my great passions: radio and the history of the Cold War. I chose to visit two historical sites that also serve as a reference point for the POTA (Parks on the Air) ham radio program, allowing me to transmit with my radio in these unique locations.

The first location is a park located about a kilometer away from where I worked for a week, the headquarters of RBB, the public radio and television of Berlin and Brandenburg. This park is Teufelsberg, which literally means the Devil’s Mountain. It is an artificial hill in Berlin, created using the rubble from World War II, located within the Grunewald forest (POTA reference DA-0218).

On this hill, the Teufelsberg listening station of the American NSA in Berlin was situated, which was used to intercept radio signals from East Germany during the Cold War.

Today, you can still see the remains of the antenna covers of the listening base. I activated the Pota park that has been established around the abandoned base, and I was delighted to transmit my signals in Morse code (CW) in QRP mode in this historically significant place.


I used the small QMX transceiver from QRP Labs, a gem for operating in FT8/CW modes on the 80/60/40/30/20 meter bands.

For an antenna, I used a 20-meter wire connected to an EFHW 49:1 balun, hung above a tree. Amid families flying kites, I made 15 CW QSOs, which allowed me to validate the park activation. The program requires a minimum of 10 QSOs for activation to be valid.

The second activation took place in another symbol of the Cold War: the runway of the former Tempelhof airport. I activated this as a POTA site and transmitted CW QRP with the small QMX transceiver from QRP Labs in the fog and cold.

The Berlin-Tempelhof Airport was an airport located in the southern part of the central Tempelhof-Schöneberg district and was operational from 1923 to 2008.

It is famous for hosting the Berlin Airlift base (1948-1949), which was an incredible operation undertaken during the Cold War by the United States and their Western European allies to transport food and other essential supplies to West Berlin, surrounded by the Soviets.

Today, the airport is closed, and its runway has become a massive park (POTA reference DA-0169) used by Berliners for various outdoor activities. I activated it early in the morning on a gray and cold day, setting up my EFHW antenna practically on the runway.

Again, I used only CW, and in no time, I reached the number of 11 QSOs. The cold made me stop the activity earlier than planned, but the activation is still valid. After concluding the transmissions, I walked through the enormous park, imagining its past use and appreciating how often my amateur radio passion leads me to incredible places.

This was the first test of this “minimal” POTA kit with the QMX transceiver, the 20-meter EfHw antenna, and the XTPower XT-16000QC3 12v power bank.

I must say that the test was successful. This is an excellent little radio that I want to use and take with me on every work trip. The POTA program continually takes me to incredible places, both in terms of nature and history, as it did in this case in Berlin

Field Radio Kits, Grab And Go, News, Portable, QRP

Field Kit Gallery: KM4CFT’s QRP Labs QMX/QCX-Mini Go Kit

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Many thanks to Jonathan (KM4CFT) who shares the following article about his portable field radio kit which will be featured on our Field Kit Gallery page. If you would like to share your field kit with the QRPer community, check out this post. Jonathan writes:

Hi Tom,

I thought I would share the two go kits I have. I tend to customize my equipment and supplies before I go on a POTA or SOTA outing but I keep these for the rare occasion when I want to grab a radio real quick. [The first on is my] QRPlabs go kit:

The kit is for my QRP Labs QMX/20 meter QCX mini. It contains everything I need to operate 20 meters CW.

The case is a regular Lowepro case that I got with my KX2 when I purchased it from another ham. I did not realize it came with it so I accidentally ordered an extra from Elecraft which I now use with the KX2 kit [featured in a future Field Kit Gallery post].

The kit uses many components from K6ARK, including the 20 meter EFHW antenna and the retractable paddle.

The battery is a TalentCell from Amazon. I use it because it supplies 12v instead of 13.8v. One of the downsides of the QMX is that it cannot handle 13.8v, so I have to stick with 12.

I keep a cheap pair of earbuds with me just in case but I try to bring a nicer pair of headphones whenever possible.

Hopefully this information is useful to you and your readers!
-Jonathan KM4CFT

Readers: Check out Jonathan’s YouTube channel by clicking here.