Tag Archives: QRP Labs QCX-mini

QCX Mini 20 Meter Build

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Yesterday I posted about my latest QCX mini kit from QRP Labs arriving. I had intended to wait until the weekend do dive into the build, but…

I couldn’t wait.

As I mentioned before, QRP Labs publishes incredibly well done documentation in their build instructions. You can see the latest version as of this writing here.

I ordered about a week prior, and it arrived via FedEx delivery in good shape and with everything well packed.

The kit is not necessarily difficult if you’ve built similar radios before, but I do recommend reading the manual through one time before starting. Everything is straight forward, but after a couple of hours of huffing solder fumes, it is easy to miss something and having read it first keeps things in mind along the way.

After taking stock of all the parts, I simply followed the manual step-by-step.

This is not a “how-to” post, rather a pic heavy of the steps I took when assembling.

First up is the *dreaded* T1 winding.

For 20 meters, it is 3×3 turns, with 1×30 turns

Actually T1 is really straightforward and simple to wind – if you read the instructions! The main point of the way they instruct you to wind it is so that all windings are the same direction. I think there are two in particular that have to match, but it is easiest to match all of them at the same time.

Soldered, checked, and ready for the next steps

With so many leads coming off of the toroid, taking it slow is needed. But again, follow the well laid out instructions and it comes together nicely.

Next up is the IC socket. Simple stuff, just make sure the notch is in the right place.

Capacitors are multiplying!
Band Pass Filter windings starting to show up
Main board is starting to get crowded

The Main Board comes together pretty quickly – there really isn’t a lot of parts to this kit that are not SMD and already on the board.

Next – moving on to the Display Board and Controls

The display is secured into place prior to soldering

NOTE: Do not toss the clipped leads from the components you’ve already soldered. You will need them for soldering the display leads. Take some of the clippings and use them as connections for the display to the PCB.

Soldering all the makeshift leads is – in my mind – the most tedious part of the build

I failed.

I didn’t remember to take any photos prior to the final smoke test shot below, but it is just mounting connectors and doing final connection checks prior to putting in some power and seeing if we let the “magic smoke” out or not.

Success!!!

If all goes well, then upon first boot up you should see the above.

No magic smoke erupted, and it was time to get into calibration.

Calibration in progress
The whole QCX-mini “sandwich”. Very tight tolerances, but if you follow the manual it all fits the first time

Due to the tight tolerances of the kit and the optional case, I choose to line the case with electrical tape to avoid any potential of having any contacts cause any issues.

It is also recommended to take a moment to ensure that any soldered leads are closely trimmed prior to casing it up.

The kit in its new clothing – I highly recommend the optional case for this little radio as it is well made and fits like a glove

Conclusion

I cannot recommend this kit highly enough. They have created a well laid out kit, manual, and final product. The size of this thing is tiny – but having full-band CW coverage, with additional modes like WSPR puts it in a category all its own.

If they came out with a multi-band CW rig – even only 20/30/40 meters – they would absolutely kill the QRP POTA/SOTA market.

Even so, for the price and size, having 2-3 of these is not too much. This is my second purchase from them and I’m already contemplating a 3rd.

Go get yours at https://qrp-labs.com/

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This year I decided to learn CW (for the nth time).

I mean to finally learn CW and actually use it going forward. I also wanted to start operating from the field as much as possible.

As such, I started to acquire some mobile rigs – mostly QRP – to push me to make good on my investment and spend the time practicing CW and getting on the air. The good news is that I made my first CW contact on Memorial Day this year. My QTH introduces a lot of RFI so the QSO was quick and dirty, but we exchanged callsigns and actually did a follow up email or two.

I’m hooked.

However I looked around my home office and realized that I’ve got a few rigs now.

Quite a few.

So I’m putting together this comparison chart both for my own reference, but hopefully for yours as well.

Now, which radio to use next…..

RadioModesBandsWattsVoltageNotes
Elecraft KX3All160m-6m0.1-109-15VDCThe Cadillac of my QRP rigs
Xiegu x5105All160m-6m0.1-59-15VDCBuilt in 12v 3800mah battery
LnR Precision MTR4B v2CW40m, 30m 20m, 10m55.5-12VDCDo not use more than 13v supply
Ten-Tec R4020CW40m, 20m59-14VDCCan receive SSB
QRP Labs QCX-miniCWSingle Band (mine is 40m)57-14VDCKit – high quality components, great documentation
Many options, each with its own awesomeness

Random Thoughts

Largest to smallest, which almost corresponds to feature sets as well

Elecraft KX3

I do not know where to begin. I purchased mine used and upon first boot, was blown away by the receive capabilities, filtering, etc. It is a robust, feature-rich, and portable transceiver that checks all the boxes and does so in a first class manner

Xiegu x5105

This is the latest addition to my kit. Radioddity.com had a great 2021 Field Day sale on these that came with the CE-19 adapter and a custom backpack. I took this in the woods all last week in northeast Wisconsin. The built-in battery pack that can be charged while it is in use is amazing. The retracting feet put it at just the right viewing angle. There are some nits such as latent noise when on headphones, but being slightly smaller (and significantly cheaper – less fear of breakage) than the KX3 means that I’m looking to use it more often.

LnR Precision MTR4B v2 (Mountain Topper)

Wow. So on opening the package I was amazed at the build quality here. Sturdy case, compact size, and a lot of built in features make this little rig a favorite of mine. Part of the compactness means that you give up a couple of things that other rigs offer – no volume control (watch those strong signals), no ATU (use a resonant antenna – problem solved), and a lower voltage input before you start to max out the PA FETs. It has built in message memories, beacon mode, and more.

The voltage input is the biggest issue with me for this rig – I have a couple of 3s LiPo batteries that I use just for this radio – but that is a minor nit given the great receive and overall performance that comes with it. Given that you can run this thing off a standard 9v smoke alarm battery, I’m not complaining (too loudly 😉 )

By the way, Amazon has a great and inexpensive case that fits the MTR4B v2 and power cable with adapter for Powerpoles to XT-60. You can find it here.

TEN-TEC R4020

I picked this up the last time I thought I was going to learn CW. It has largely sat unused fora few years, but I do pull it out on occasion. Small, easy to use, and built in AA battery tray (bring a screwdriver to open/replace batteries). Not much to say here other than it is capable and when I bought mine on Ebay, was relatively cheap for the quality.

QRP Labs QCX-mini 40m

This is a kit build and I strongly recommend it as both a great build experience and a great little radio. It is half the size of the LnR Mountain Topper above, has a built in CW decoder, volume control, message memories, and more. With the exception of one toroid that is somewhat more complex to wind than most I’ve done, it goes together easily with some of the most comprehensive and easy to follow instructions that I’ve ever seen in a kit. If you want to dive into kit building, or just want another one to add to your shack, I cannot recommend this one highly enough. For the price (<$100USD with a solid metal case), it is top notch.