I waited 6 months for my factory assembled QRP Labs QMX to arrive – was it worth the wait? Really?

Was it worth the wait? Oh, yes! Let me say up front that I could have ordered the kit version and received it much faster, but my aging eyes just aren’t up to the job of all that delicate soldering work. But, eventually, it arrived and I couldn’t be more pleased. So how am I getting along with it?

Clicks and Thumps

While waiting for my order to slowly climb the waiting list I joined the discussion group at groups.io. Some of the posts were quite alarming. One particular issue seemed to generate a lot of comments – clicks and thumps while operating the QMX in CW mode. I was alarmed. It can be difficult enough to work through pile-ups, or copy weak signals without the distraction of extraneous noises. I asked Hans Summers, the owner of QRP Labs, for his comments. Hans responded that fixing this issue is his number one priority. My QMX has firmware version 17 installed. I understand that the fix is included in firmware version 18. I will, in due course, download and install version 18 but frankly, careful adjustment of the AGC settings renders the clicks and thumps quite manageable.

First QMX POTA Activation

Following a “getting to know you” series of “Backyard On The Air” QSOs I took my new “Tiny Turk” QMX out for its virgin POTA activation. Could such a teeny-weeny little radio deliver what it takes to get a successful Parks On The Air activation in the logbook?

Propagation conditions were not good but Tiny Turk got the job done even though I only managed to squeeze 11 QSOs out of the ionosphere. I chose a local conservation area, Colpoy’s Lookout, whose elevation is about 100 feet above the level of Georgian Bay – part of Lake Huron – but which favors east-west propagation. Most of my QSOs are with stations to the south. Unfortunately the Niagara Escarpment rises another 200 feet immediately to the south of this park. It was a good test for the QMX but Tiny Turk rose to the challenge.

What’s Not to Like About the QMX?

It is hard to criticize a radio for its shortcomings when it is still under development. The QMX is a work in progress. QRP Labs owner Hans Summers has stated that he decided to release the product as soon as the hardware was ready. New features, bug fixes and other changes and improvements come later in new firmware releases.

1. Size Does Matter

So what about the hardware? First, the very small package size is one of the QMX’s greatest strengths and biggest drawbacks. I bought the QMX to replace my aging Hendricks PFR3. The PFR3 is a small radio but it is bigger than the QMX. But, the PFR3 has an internal Z-match manual tuner and has room in the case for a set of AA-size batteries. I don’t own the very popular Elecraft KX2 but it also packs an internal tuner and battery inside its case. The QMX has to be powered by an external battery and must be used with a resonant antenna or with an external antenna tuner. The advantage of its tiny size is lost if bulky external components have to be added.

2. Whoa … not so loud!

The audio amplifier in my QMX seems to have too much gain. If the left rotary encoder is turned up enough the audio gets boosted – a lot. That may be great for weak signals, but the background noise also gets boosted to the point where a loud screeching noise is heard. I don’t know whether this is a bug in my unit or an issue with all QMX radios.

3. Low bands, high bands, medium bands – choose

The QMX is limited to 5 or 6 bands – not much of a limitation at all really considering the original QCX series of transceivers from QRP Labs were single band radios. But still, it forces buyers to choose between one of three options:

• 80m, 60m, 40m, 30m, 20m
• 60m, 40m, 30m, 20m, 17m, 15m
• 20m, 17m, 15m, 12m, 11m, 10m

I chose the low band version because that is where I spend most of my operating time. I don’t use 60m at all so effectively I have a 4-band radio. My ideal band combination would be 80m, 40m, 30m, 20m, 17m, 15m and 10m – yes 7 bands. If 6 bands is the limit then I could manage without 80m.

I am not an RF engineer, but isn’t the frequency generated digitally (i.e. in firmware)? So is the band selection simply limited by the Low Pass Filters? It would be nice if users could select their own choice of bands.

4. DC Voltage Supply

First, I don’t like barrel connectors. The QMX uses a 2.1mm barrel connector which fits nice and snug but a sharp tug will pull it out. How would the QMX respond to having its DC supply disconnected before it has a chance to go through its shutdown routine? I don’t know the answer to that question and I really don’t want to find out in the middle of a POTA activation. Why would this happen? Imagine balancing QMX and battery on a kneeboard while perched on a camping stool. Those pesky mosquitoes decide to eat you for lunch; you swat wildly at them and all your gear tumbles to the ground – yes, it has happened to me.

Like other small radios (my PFR3 included) the DC supply is recommended not to exceed 12 volts. Most batteries do exceed 12 volts – sometimes significantly so. Desktop radios will accept a wide range of DC voltages, so why not the QMX? Perhaps that is a consequence of very tight packaging. Again, I don’t know, but it does mean that external voltage control is needed. I use a pair of series diodes to bring the supply voltage down to around 11.7 volts. I wonder whether there is room inside the QMX for a couple of diodes? Maybe not.

What’s to Love About the QMX?

1. SWR Protection

I really like the way this feature is implemented. Most transceivers have a “fold-back” function which reduces the output power when a high SWR is encountered. As I understand it, the QMX will inhibit transmission if the SWR exceeds a threshold set by the user. I chose that limit to be 3:1.

2. SWR measurement

SWR can be displayed during operation as a bar graph at the top right of the display screen. For a more detailed measurement there is another tool available as shown in the image below. Since we know the radio is protected against high SWR, this diagnostic can be used with confidence to measure the SWR seen by the radio. Of course, it must be remembered that the SWR at the antenna feedpoint may be quite different. To further protect the transmitter finals, the SWR measurement tool allows the voltage to be reduced (and thereby the output power too) by a user selectable precentage.

So can I leave my trusty RigExpert antenna analyzer at home now? I think so, but maybe I’ll bring it along for the ride – just in case.

3. Message Memories

The QMX has 12 message memories. I love this feature but I currently only use two of them. Oftentimes, a POTA activation involves a lot of CQing to get a response. Instead of the tiring process of keying the same CQ message over and over, a simple button click will send a recorded message for you. And you can let the QMX repeat the message automatically after a user selectable interval. I set the interval to 5 seconds – enough time to listen for a response and stop the next repeat. A simple tap on the paddles will cancel the automatic message repeat. My pre-recorded messages are my CQ POTA and my callsign (which is useful when battling a pile-up as a POTA hunter).

4. The Price!

Most full-featured QRP transceivers cost an arm and a leg but the QMX is very moderately priced. If I didn’t have to wait so long I would probably order the other two band options too!

4 Thumbs Up but 4 Grumbles too? What Gives?

Think of it as a baseball game. The score at the end of the first inning doesn’t mean a heck of a lot. When it gets to the stretch we’ll get a better idea of where we’re headed. An all-star batter (Hans Summers) is at the plate and he has already hit the ball out of the park by producing this amazing little gem in the first place! And there’s still at least 8 innings to play.

And what new features would I most like to see?

• Anderson Powerpole DC connector instead of the barrel connector
• DC voltage regulator to allow common battery types like LiFePO4 to be directly connected to the QMX
• User selectable choice of bands
• All band coverage? Ah, that’s another beast entirely. It’s called the QSX and it will be a 10-band, 10 watt transceiver – but it’s still under development.

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