Category Archives: Kits

A Strong Case for the (tr)uSDX: Jamie’s Perspective

Readers, there’s a bit of a backstory to this guest post by my friend Jamie (AA4K). During the W4SOTA campout in October 2023, Jamie showed me his favorite field radio: the (tr)uSDX. I’ve used the (tr)uSDX for a couple of activations, but I’ll be honest—I haven’t exactly shown it a lot of love. I’ve even complained about its audio and receiver performance in the past. Jamie, on the other hand, really enjoys using his and makes a solid case for it as a field radio.

Jamie showing me his (tr)uSDX during the W4SOTA campout.

I asked if he’d be willing to write a guest post for QRPer, and he agreed (eventually!). When I saw him at Hamvention this year, he told me the article was ready—and in true form, he sent it to me via Winlink… using his (tr)uSDX.


A Case for the (tr)USDX

by Jamie (AA4K)

Introduction

There are many factors that must be considered when choosing a field radio. How big and heavy is the radio? How hard is it to repair or replace the radio if it becomes damaged or lost? How hard is the radio to operate? How power-efficient is the radio? Does the radio have the desired/required modes and features? Of course, the most fundamental question is, “Does the radio work?” I will try to answer these questions as I lay out… a case for the (tr)USDX as perhaps an almost perfect field radio.

The last two contacts on this page were with my friends Carlos (KB4CO, now AE2W) and Thomas (K4SWL).

How big and heavy is it?

The first question is an easy one. Aside from small home-brew radios such as K6ARK’s “Choking Hazard”, there isn’t a smaller or lighter commercially available radio out there that I am aware of. The (tr)USDX measures 112 x 61 x 50 mm (I trimmed the encoder post and used a lower profile knob), and weighs 5.3 oz, or 151 g. The next closest currently available commercial radio is perhaps the QRP Labs QMX. This radio is very comparable in size (110 x 64 x 38 mm) and cost, but it does weigh more at 7.3 oz, or 207 g. The more rugged metal case probably plays a big part in the weight difference.

(tr)USDX with a modified case I designed to use the radio as the antenna winder.

How hard is it to replace or repair it?

The (tr)USDX is often sold as a kit for about US$86 (+$20 for the case) [QRPer affiliate links]. Any repairs should simply involve desoldering affected components and replacing, or possibly just updating the firmware. I am a relative noob when it comes to kit building and this kit is honestly not very difficult to build… about one day. The instructions and support videos provided by the hardware developer, Manuel DL2MAN, are very thorough. I learned a lot about radios from building the kit. If you have no interest in kit building, the assembled radio can currently be purchased from Amazon for US$138, complete with a case. Whether purchased as a kit, or already built, the band pass filters on the radio board will need to be tweaked to get the most out of your radio.

How hard is it to operate?

The (tr)USDX only has 4 buttons including the rotary encoder: Menu, Encoder, Enter, and PTT. The Menu and Encoder cover the majority of the adjustments, and most of the time I don’t use the Enter and PTT buttons. The PTT functions only as a ptt or cw key depending on the mode (yes, if your key breaks mid activation, you have a built-in backup key). The single-layer menu system is simple to scroll through, and the most commonly used items are near the front of the menu.

The most challenging aspect of operation for some people is the tiny OLED screen which gets obliterated in bright light. Reading glasses do help, although when you become familiar with the menu are not as important. I would love to see a version with an e-ink display and, more importantly, a push-button wheel rotary encoder (to remove the protruding knob).

How power-efficient is it?

This radio sips power. I tested the radio I built using a LiFePO4 battery that supplied 13.56v. The current draw on receive is 66.1 mA, and 570 mA on CW keydown into a dummy load. A properly tuned (tr)USDX delivers about 5w on each of the five bands when fed ~12v. A set of three 18650s in series will provide the proper voltage and power the radio through many activations.

Does the radio have the desired/required modes and features?

The (tr)USDX is not for princesses. It is a minimalist’s radio. But if you start from the perspective of an ultralight backpacker who has to justify every gram in their kit, this radio checks all of the boxes. It is a five band radio (Low, Classic, and High band models available). It is capable of doing voice, cw and digital modes. Thanks to a beta update from the firmware developer, Guido PE1NNZ, this radio will interface with a computer without requiring a soundcard. One of my favorite features of the radio is the built-in SWR meter. With the SWR feature enabled in the menu, just put the radio in CW mode and press the PTT to find out if your radio is happy with the current antenna arrangement.

This photo was taken while sending the text of this article via Winlink to Thomas, K4SWL.

Does the radio work?

Although my total activation count is nowhere near as high as many of you, I have used the (tr)USDX for a majority of my successful POTA (156 as of this writing) and SOTA (72 as of this writing) activations. My confidence in this little radio was demonstrated when I used it on an ATNO activation of Admiralty Island National Monument (US-4537) in Alaska.

Conclusion

One reason why I like to participate in SOTA and POTA is that it gives me an opportunity to practice field radio deployment and operation with the goal of being ready to communicate anywhere and anytime. This level of readiness means that I have the necessary equipment with me all the time. For me, the (tr)USDX is my EDC (every day carry) radio. It can bounce around in my backpack (in its protective case, of course) and be ready to deploy if needed. If it were to get lost or broken, I can fix or replace it easily. And I find it to be easy enough to use with the understanding that it isn’t a luxury radio.

The author at ~11,000’ in Uncompahgre National Forest.

Video

Click here to view on YouTube.

(tr)uSDX Winder Case:

Click here to download the print file for Jamie’s the modified (tr)uSDX case.

The New KM4CFT KX2 and KX3 Iambic Paddle Kit

My friend Jonathan (KM4CFT) recently sent me a neat little prototype paddle he designed for the Elecraft KX2 and KX3 field transceivers.

He wanted my feedback, so he generously sent me a set to evaluate at no charge.

Lately, I’ve been tied up with the final stages of debris cleanup here at the QTH, leaving little time for field activations. While I haven’t had the chance to take these paddles out into the field yet (stay tuned!) I’ve thoroughly tested them on both my Elecraft KX3 and KX2. In the meantime, Jonathan has made the kits available for purchase on the HamGadgets website.

The price? $49.97 — a solid deal for a simple, functional paddle designed to plug directly into the front of the KX2 and KX3.

Assembly is quick and straightforward, taking around 15-20 minutes. There aren’t many parts, and the mechanics are refreshingly simple. If you’re curious, you can check out the kit assembly manual here (PDF).

My Impressions

I think it’s an excellent little key for the price. The paddle action is light — the 3D printed material keeps them featherweight, making keying effortless.

For field use, they should perform brilliantly. The light touch required keeps things stable on a table, with the KX2 or KX3 providing more than enough weight to prevent the paddles from shifting as you operate.

The operating angle works well for me too. I know Jonathan put a lot of time into getting this right during the design process — and it shows.

Any Downsides?

The biggest drawback, in my opinion, is that the two thumbscrews securing the paddles to the front of the radio aren’t captive.

This means they can be easily lost during transport. I recommend storing the paddles in a thick poly bag to keep everything together in your pack.

Additionally, because the screws aren’t captive, you need to be a little careful when installing the paddle. I’ve found it easiest to place the radio on its back, so you’re screwing the thumbscrews downward.

I lightly plug in the paddle, then start threading both screws before fully tightening either one. This gives me better control and helps avoid dropping the screws — something that could be a real headache in the field, especially if they hit the ground.

Lastly, these paddles don’t have the “precision key” feel of more expensive options. But to be fair, they’re designed as an affordable alternative to Elecraft’s KXPD2 paddles, which retail for $169.95. Even the KXPD2 — while smaller and sturdier — doesn’t feel particularly “precision” in use. The KX3 paddles come closer to that, but they also cost $239.95.

At $49.95, it’s hard to complain — these paddles do exactly what they’re supposed to do without breaking the bank!

If you’ve held off buying front-mounted paddles for your KX2 or KX3 because of the cost, I’d highly recommend giving these KM4CFT paddles a try.

Click here to check out the KM4CFT KX2/KX3 paddles on HamGadgets.

The Design Philosophy of the CFT1: From concept to product

Many thanks to Jonathan KM4CFT who shares this article with us.  If you have an article in your head and want to have it posted here, let’s keep this community going while our friend Thomas continues to help his neighbours. Draft up your story in an email with reference points to the pictures you want embedded and their captions, attach photos to the note and send it my way to vincedeon at gmail dot com and note QRPer in the subject line to get my attention.

By: Jonathan Kayne, KM4CFT

About 10 months ago, I took the plunge to design my own Morse Code transceiver. It was a crazy idea, and this was certainly a massive undertaking, but somehow, I managed to pull off this monumental task. The result of the project was the CFT1, a 5 Band CW Field Transceiver specifically tailored for POTA and SOTA operations. Doing this project was a great learning experience and despite the monumental effort and work I put into it, I really enjoyed getting to design a new product. There is something special when you see something you love and put effort into appear in the hands of others and seeing them enjoy using said product.

The purpose of this article is to outline some of the thoughts I put into when I designed the CFT1. It is not meant to go into the meat and potatoes of RF design work as there are plenty of resources out there that go over that stuff. I have yet to see much discussed on design philosophy of a transceiver so I thought it prudent to document these things. That is; what I took into consideration when putting together the radio. And as I learned in this project, when pulled off correctly, can result in a great product.

Continue reading The Design Philosophy of the CFT1: From concept to product

Video: Alan (W2AEW) Builds the CFT1 5-Band CW Field Transceiver

Our friend Alan (W2AEW) has just posted a video showing the process of building, adjusting, and aligning the CFT1 5-band CW portable transceiver. If you’ve been thinking about building a CFT1 kit, this video will help guide you [update: see note from Alan below]:

Click here to view on YouTube.

Thank you for making this tutorial, Alan!

In Stock: The Ham Radio Workbench Podcast DC Distribution Panel Kit

Many thanks to Mike (KG4MTN) who notes:

Hi Thomas,
Just a note to let you know that digikey has a supply of Ham Radio Workbench DC Power Strips in stock, 43 at the time I reviewed. Product number is HRWB101.

Thought you might want to let your audience know. These are neat little kits, I really like mine!
72,
Mike Serio
KG4MTN

Thanks for the tip, Mike! These will likely sell out quickly.

I may be biased, but I love mine! Such a handy accessory and easy kit build.

Click here to purchase one via DigiKey!

KM4CFT Teases a New CW Field Radio!

My buddy, Jonathan (KM4CFT), is close to releasing a new CW Field Transceiver kit he designed for POTA, SOTA, and pretty much any other field radio activity.

Today, he shared the following photo, which is a bit of a teaser:

Those of you who attended Four Days in May this year may have already gotten a proper sneak peek and even operated a prototype of this radio.

Jonathan tells me that he’ll be releasing details in the near future and you’ll soon be able to order the kits via Radio Dan’s eBay store [eBay partnership link] or via his website.

Of course, I’ll also post details here on QRPer.com when the new radio kit is live and ready to order! Stay tuned!

Sam’s Thunderbird Mk 1 Takes Flight: A Homebrew Radio Field Report from the American Southwest

Many thanks to Sam (WN5C) for sharing the following guest post:


Homebrew in the Field

by Sam (WN5C)

What a week it’s been!

I have the opportunity to spend a month traveling through and camping in the American Southwest (specifically, New Mexico, Arizona, and Colorado) doing archaeological work. And of course, that means the prospect to operate portable at weird times and in lots of places.

I’ve been planning for this trip for a couple of months, about the same length of time that I’ve been trying to achieve my amateur radio dream: to build a complete transceiver. So why not try to do both things at once?

This is just a quick note of my experiences in the first quarter of my trip of taking a homebrew rig into the field.

First off, I have absolutely no background in RF engineering, or electronics at all. But the literature is good and Elmers are priceless (thanks Kenn KA5KXW!). I started small, with kit projects, and then very basic transmitters.

I’ve always appreciated how much satisfaction my father gets by building things by hand, and finally I have a similar hobby. I called the radio I designed the Thunderbird Mk 1 based off the fact that I cut my CW and POTA teeth at Lake Thunderbird State Park in Oklahoma and will probably continue to work there the most. It’s a 6-band (40, 30, 20, 17, 15, 10) CW QRP transceiver with SSB receive.

The receiver is direct conversion and is an amalgamation of VU2ESE’s DC40, KK7B’s Classic 40, and W7EL’s Optimized QRP Transceiver. The VFO is an Arduino/si5351 combo based on the schematics and code written by VK3HN (who has helped me from afar, thanks Paul!). It’s crude, but I use a 6-position rotary switch to manually switch between the band-pass filters.

The transmitter is based on W7ZOI’s Updated Universal QRP Transmitter, married with VK3HN’s Arduino code that acts as the oscillator, keyer, and side tone generator. I get about 3 watts output for 40, 30, 20, a little less for 17 and 15, and about a watt on 10 meters. Like the receiver, I manually switch the low-pass filters.

Here’s a picture of the digital parts (ignore the second Arduino Nano, I thought I would need it but did not), the power board, and the filters. It’s on the bottom:

On top is the main board with the receiver, the transmitter, and T/R switching. Also, you’ll notice the green PCB. I *really* wanted to build NM0S’s Hi-Per-Mite from scratch but I couldn’t get the circuit to run right before my trip so I opted to install one that I built from a kit. It’s a fantastic CW audio filter that I can switch in and out (everyone should have at least one!).

I can switch in a little speaker and added a straight key jack. I printed the box on a 3D printer at the local library. It works great for the shack. In the sun, it’s starting to warp in the heat, so I’ll have to address this, but things still work!

Getting out the door on time with a finished radio was tough! I had finished right before I left on my trip (end of May 2024) and had no time to field test. The best I got was taking the rig to the table in the back yard and firing it up during the WPX contest.

I made amazing DX contacts on all the contest bands I had and called it good. But working superstations isn’t real life, and over the next week I’ve had to MacGyver the radio (rigging a car jump pack, an inverter, and a soldering station together at a picnic table to replace a bad transistor, for example). I think I’ve finally shaken out (literally) all of the loose solder joints and bad grounding. Continue reading Sam’s Thunderbird Mk 1 Takes Flight: A Homebrew Radio Field Report from the American Southwest

Build Your Own VK3IL Pressure Paddle: Alan’s (W2AEW) Step-by-Step Video Tutorial

Our good friend Alan (W2AEW) has just posted a video on his excellent YouTube channel showing how to build the VK3IL pressure paddle. He also explains how the key works using the schematic and gives tips for working with the surface mount components.

This paddle is an exceptional key and quite inexpensive to build!

Click here to watch on Alan’s YouTube channel.

KM4CFT’s Iambic Paddle Kit for the Elecraft KH1

Many thanks to Jonathan (KM4CFT) who notified me that his new KH1 iambic paddle kit is now available to order.

I know Jonathan has been working on this little key for a while and I’m pleased to see it come to fruition.

Click here to check it out on eBay via Dan (W7RF).

Note that this is an eBay partner link that also supports QRPer.com at no cost to you!

QMX – From Kit to Field!

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!