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.
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.
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.
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.
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.
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.
I laughed when I read “…I trimmed the encoder post and used a lower profile knob…” Now that is a serious SOTA operator!
Great article (and pictures), thanks for writing it.
I love the line winder built into the radio case – brilliant!
Great article and very inspiring! I’m think I’m going to have to build a QCX-mini this year.
It is great to see this radio get some attention. The audio is harsh, but it’s easier to build than a QMX by a long shot, and the operating is system is -less complicated to remember-important for old guys (like me) that carry it as a back up.
Would love to see you modify that innovative case a bit to provide a whip mount on one side ala KH1 – or maybe design an adapter that fits on the case as designed – that could be tons of fun! Great job on the review.
There’s also a mod to fix the harshness of the audio a bit. Later revisions have that fix built-in, and they do sound quite a bit better.
Where can I find the mod to fix the harshness of the audio?
What do you mean by audio correction? If you are referring to the audio quality of the ssb, firmware 2.i is the best for my point of view.
It is the top post in the Troubleshooting forum. The forum itself is extremely useful.
https://forum.dl2man.de/viewtopic.php?t=864
Note that if you have a new board (Revision 1.1 or above), it already has this fix applied. Maybe not the tantalum caps.
Jamie:
While this rig does not fit my style of operating, I appreciate your article. I enjoy seeing how others operate and the choices they make. The details you share and your line of reasoning is extremely helpful in educating someone like myself who has no experience with this radio. I echo what other commentors said – Great job!
72,
Teri KO4WFP
The POTA Babe
Excellent article about the (tr)uSDX, I enjoyed reading it, thank you. I also own and love this radio, it’s perfect for my needs and is amazing for it’s size. My first attempt to test it was at my home QTH on an EFHD antenna and I immediately made a voice QSO with Flagstaff, AZ from NY using it’s internal PTT button and microphone. It’s the only radio that I will take in my backpack. I agree with your opinion about this radio, it’s not for everyone, especially those who expect too much from a simple QRP rig.
Jamie, you rock OM. Fun is determined by the user and you and I enjoy su per light radio kits. Your kit is an ultimate tiny station. It is always great to log you and see where you are traveling.
Although I have a few boutique radios to satisfy my addiction, I consider myself a non-princess operator and get my greatest pleasure from minimalist stations. Good to hear your perspective my friend. 72
K7ULM Dick
I got this radio a while back. Other lightweights I have are pixies, crickets and rockmites. They’re rockbound and way less power so the trusdx felt like a luxury item by comparison. It’s not something I’ve used daily. I bought it assembled. This isnt a rig I’m going to understand how it works so I didn’t think I would gain much from putting it together. Initial setup was easy. But not that long ago I tried to update the firmware and despite trying different chords and computers, it just wasn’t happening…but I decided there really wasn’t that much to upgrade anyway. That will be a problem to solve at another time. You need to use headphones or external speaker…it has a speaker but it’s not really usable. The CW filters are decent, some of them are maybe too narrow to be useful for me.
I haven’t ever activated a pota or sota. Occasionally I’ve hooked this thing up in the yard or taken it with me when out of town. But I’ve had a lot of fun with this little thing. I have an antenna I got off amazon that hasn’t really gotten very good reviews…called the goozeezoo shortwave loop antenna. There have been some not so great youtube reviews for it as well but some of the testing methods weren’t exactly as thorough as I think they thought they were being. I didn’t understand it when I got it but it’s not a mag loop like you’d think it would be, it’s an army loop. It’s on the small side. It’s not a bad quick SWL antenna either. And if you’re going to transmit through it on HF, you are going to have to replace the choke and keep in mind the radiating element is actually on the shield of the loop, and I would definitely use a choke. I don’t know what the choke was, it was tiny, I could feel the RF, so I took it out and wound one on a FT140-43 that fit inside the choke box it came with….after all that…it’s not so bad. You can’t tune it by ear (though you probably can doing SWL), at least I can’t, you have to use a nanovna or antenna analyzer and do so visually, the tuning is that touchy, and the output from the trusdx is about the max of what I’d put through it. Anyway, I’ve had a lot of fun with the trusdx and that antenna, it’s quite a challenge but you can sniff out some cw contacts fairly easily…through the walls of your house even. Its easy to use for digital modes too, in tandem with that limited antenna, you can have a single room setup and it actually makes modes like FT8 somewhat fun again. If you hook it up to a more legit antenna you’ll find it’s a little susceptible to interference but it gets out as well as anything else with 5W does. There’s pricier small hf antennas out there, I know. I made a EFRW to pair with it but rarely deploy it.
But make no mistake, this is a fun, multipurpose radio.
I own all the tabs (lo, high and classic) and agree with Jamie on the pros and cons. The trusdx does its job and quite well too. I use it only in ssb and there it is its weak point. Even the various updates Firmware failed. In my opinion the best is version 2.0i. The most difficult board to build is the rfboard But only for calibration. My favorite card is the classic. Undoubtedly the qmx competitor now that he has added to his ways also the ssb It will be the new object of desire. Also I go ordered a kit, which will definitely be harder to build than the trusdx. I almost forgot…. If you use the trusdx in ssb then the retevis hk008 microphone is a must. 73 IW2EPE
I’m with Jamie.
I LOVE my (tr)uSDX. It was absolutely the only way I could get into HF for less than $200 AND get portability and easy digital connection. Yes, I want an Elecraft, and I want an FT891, but neither of those are available in my budget at this time.
GREAT radio. More hams should have one. Doesn’t have to be their primary radio (tho it IS mine, because I have a ton of bills to pay that are more important than a radio hobby…) but it’s absolutely worth every cent.
I agree with all of the comments – the (tr)uSDX is a fun little rig. I particularly like it with the 3D printed rails that include a spot for a 9V battery: https://www.thingiverse.com/thing:5394158
I appreciate all of the kind remarks and validation
.
Very inspirational, Jamie! Thanks for taking the time to write this post. -Cliff (N4CCB)
Great article, Jamie! Glad to see you writing on QRPer.com. I’d love to build this little radio sometime soon. Your article makes a good argument for committing the time to it.
Hope to hunt or chase you soon.
Best to you & 73,
Robert (W1RMW)
P.S. – Thanks again for the K6ARK mini paddle key… still works like a charm and I use it nearly everyday!