Tag Archives: (tr)uSDX Review

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.

Bob takes a look at the (tr)uSDX

Many thanks to Bob (K7ZB) for sharing the following guest post:


A CW Operator’s First Look at the (tr)uSDX by Malahit

by Bob Houf  (K7ZB)  

April 22, 2024 – Gilbert, AZ

I recently bought an assembled (tr)uSDX from Amazon.com [affiliate link] in April, 2024, the mainboard is version 1.2 and the RF board is version 1.0.

Due to antenna limitations – a 17-foot wire antenna with a 6-foot counterpoise hanging from a second-floor condo balcony, matched through a Tokyo Hi-Power antenna coupler for an SWR well below 2:1 – I’ve been operating exclusively on the 20-meter band.

A short coax run into the dining room has given me some great on-air time over the weekend, with good band conditions for 20-meter CW.

The radio powers up when 13VDC is applied and I quickly figured out the menu structure with the minimal documentation available from DL2MAN.

I’ve learned that the filter is best set to 500Hz and it is effective for the conditions, and as the band gets hot with all the various weekend contests, I drop in a little attenuation and soon the radio begins to sound good – actually, for the money, it sounds really good.

QSK set to ON allows my keyer in Iambic B to do a good job and I don’t miss any contacts which are forthcoming across the US from Oregon out to the East coast, on down to the Virgin Islands and then, quite a surprise, my Magnificent 7 Watts is heard for a choice contact with a VK2 down under.

I pound out contest QSO’s all up and down the band, adding in a few SOTA and POTA stations and very few have trouble copying me – I certainly had no problem copying weak signals from them.

I do notice that this is not a $1,500 transceiver, especially in the receiver performance, but for the price the satisfaction derived from effortlessly working CW makes up for any limitations.

During the MST contest, as I write this, stations were piled on top of each other. I found that tightening the filter down to 50Hz wasn’t ideal – 500Hz worked better for my ears. Signals filled the band from 14.030 to nearly 14.050, ranging from very weak to extremely strong. Thankfully, the well-behaved AGC prevented any ear-splitting surprises.

I also tested SSB mode briefly and it works and sounds good, though I’m unlikely to use it much myself.

Overall, this little gem is far from a toy. With its filters, AGC, attenuator, and fine-tuning, it should bring a smile to any CW operator’s face.

Video: Taking the new (tr)uSDX QRP transceiver on a CW POTA activation!

As I mentioned in a post published three days ago, I’m now the proud owner of a (tr)uSDX QRP transceiver.

The (tr)uSDX has been a much-anticipated QRP transceiver for those of us who love playing radio in the field.

What’s not to love? It sports:

  • Up to 5 watts output power
  • CW, SSB, FM, and AM modes
  • A built-in microphone
  • Five bands: 80, 60, 40, 30, and 20 meters
  • A super compact and lightweight form factor
  • An open-source hardware and software design
  • Super low current consumption in receive
  • A super low price of roughly $89 US in kit form and $143 US factory assembled (via AliExpress, but there are numerous other group buys and retailers)

Frankly speaking, this sort of feature set in such an affordable package is truly a game-changer. Back when I was first licensed in 1997, I could have never imagined a day when a general coverage QRP transceiver could be purchased for under $150 US. The price is almost unbelievable.

My initial impressions

On Wednesday, March 30, 2022, I took the (tr)uSDX to the field to attempt a Parks On The Air (POTA) activation. I had only taken delivery of the (tr)uSDX about 15 hours beforehand and had only had it powered up for a total of 30 minutes the previous day. Most of that time, in fact, was checking the power output at various voltage settings into a dummy load. I did make one totally random SSB POTA contact shortly after hooking the radio up to my QTH antenna.

I knew that taking the (tr)uSDX to the field and making an activation video might not be the best idea having had so little time to play with the radio and get to know it in advance, but then again, I was simply too eager to see how it might perform.  That and I always believe there’s value in sharing first experiences with a radio. Continue reading Video: Taking the new (tr)uSDX QRP transceiver on a CW POTA activation!

The (tr)uSDX QRP transceiver: My initial impressions after a CW POTA activation

I mentioned in a previous post that I placed an order for a (tr)uSDX kit with roWaves in February. My order was placed for a third production run kit and I assumed I would receive it sometime in March 2022.

Later that month, I discovered that DL2MAN announced AliExpress would sell both kits and fully-assembled versions of the (tr)uSDX. I used the link from DL2MAN’s website and ordered a fully-assembled unit.

My thinking was that I would receive the kit first, build it, then test the performance by comparing it with the factory-assembled unit. These units are so dang affordable I felt like I could splurge for both.

roWaves order on hold

I recently discovered that my (tr)uSDX kit had been placed on hold due to issues that popped up in the first and second kit group buys via roWaves.

Evidently–and someone can correct me if I’m wrong here–the first and second production runs kits had a component issue that equated to lower output power. In addition, Josh (KI6NAZ), reports that the early group orders had no boot loaded and the MCU was DOA.

I’ll patiently wait for roWaves to sort this out. I’m not in a huge hurry at this point because, frankly, my available time to build a kit has come and gone. The next few months, I’ve a lot of plans, travels, and projects to work through.

Fully-assembled (tr)uSDX

Much to my surprise, the assembled (tr)uSDX arrived Monday and I picked it up when I was at home on Tuesday of this week.

I was only home one night, but managed to do some quick testing.

I soldered Anderson Powerpole connectors on the supplied power cable pigtails. Next, I hooked the (tr)uSDX up to my variable power supply and a dummy load.

A quick test showed that I was getting about 3 watts of output power with about 13-13.2 volts, 3.25 watts at 13.8 volts, and 2 watts of power with 9-10 volts. This is lower than the expected 5 watts of output power @ 13.8 volts. The current consumption in receive however was about 60 mA even at 9 volts. That’s slightly below the published specs.

I honestly had no time that evening to play radio, but I took a moment to hook up the (tr)uSDX to my skyloop antenna just to check the audio quality in SSB.

As luck would have it, the first station I heard on 40 meters was a POTA activator in Ohio. He was calling CQ, so I couldn’t help but reply. I pressed the PTT button on the (tr)uSDX, spoke into the internal mic,  and he came back immediately with a 5×8 report. My meter was showing a max of 2 watts output power–the heavy lifting, of course, was done by the antenna.

This gave me a very good initial impression!

(tr)uSDX POTA Activation

The following morning, after running a few errands and carting my kids to some appointments, I left the QTH for a couple nights of travel.

I just couldn’t help but pack the (tr)uSDX and attempt a park activation en route. My goal was to see if it had enough positive receiver characteristics to be a proper POTA/SOTA portable rig–the feature set is comprehensive for a $135 radio.

I stopped by South Mountains State Park and paired the (tr)uSDX to an EFHW my buddy Steve (MW0SAW) kindly built and sent me. [Steve–I’m loving this antenna! Thanks again, OM!]

I made a video of the entire activation and will soon post the field report. I’ll push this video to the front of the line, but with my internet bandwidth, it might still be a few days before I can post it. Because of this, I thought I’d go ahead and share some of my experience with the (tr)uSDX in case you’ve been thinking of purchasing one.

(tr)uSDX pros

This little radio design has a lot going for it.

The chassis is very compact–perhaps the size of two Altoids tins stacked on top of each other. The encoder does protrude–in fact, it’s nearly as deep as the radio chassis. It’s not that the encoder is particularly tall, it’s just that the (tr)uSDX is so wee.

The radio has all of the CW adjustments you’d typically find in a compact field transceiver and even sports QSK (there’s also a semi QSK setting) with no relay noise. I assume it uses PIN diode switching.

(tr)uSDX Cons

Unfortunately, I did find a few negatives. The reviewer in me automatically gives the (tr)uSDX wide berth and a lot of forgiveness: we’re talking about a $135 transceiver here. I don’t think anyone is under the impression this would be a stellar performer.

In my opinion, the biggest negative is the (tr)uSDX audio. This little rig has a very high noise floor–perhaps S5 or S6.

The internal speaker is very modest and mine is incapable of producing audio at a level that is workable in the field where there are ambient noises like wind, water, conversations, birds, etc. The audio sounds decent when working a strong station, but weak stations are extremely hard to hear. If you turn up the volume on my unit beyond level 14, the audio simply squeals. I need to tinker with the volume control more.

Since the audio was so weak, I hooked up my Sony digital audio recorder to the (tr)uSDX headphone jack and made a separate audio recording for the upcoming activation video.

The headphone audio is louder, but there’s also a lot of noise in the audio amplification chain–again placing the (tr)uSDX noise floor around S5 or S6.

I was fully expecting the (tr)uSDX receiver to overload and it does. The variable filter helps and narrowing it makes the audio sound more pleasant in CW, but it doesn’t stop adjacent signals from bleeding through. Honestly, though? I could live with this and just use the filter between my ears if the audio was simply cleaner.

I also discovered that my unit needs alignment: the frequency display is off by 1.6 kHz in CW mode on 40 meters. I’ve put this on my to-do list–after all, this is a project radio meant for hands-on tweaking. I’m good with that.

One final point and minor quibble: the OLED display is very difficult to read outdoors. It’s superb indoors, but outside any sunlight or reflection simply wipes it out. To read the display I had to cover it with my hand.

The activation was a success: I worked 11 stations in 20 minutes or less, but I’m sure there were weaker signals out there I missed because they were simply buried in the (tr)uSDX’s noise floor.

I liked the (tr)uSDX keying, and I love the form factor, but I’m not sure I’ll ever use this radio again–configured as it is now–during an activation. For casual contacts, it could still be fun.

A little (tr)uSDX grace

I mean…$135 right?!?

The (tr)uSDX is an open source project and truly pushes the boundaries of what one can achieve for $135–again, even much less for the kit version. Frankly, I’m in absolute awe that any transceiver can be made below the $150 price point; especially a multiband, multimode transceiver.

The (tr)uSDX is an experimenter’s radio and I plan to dig into this little unit and see if there’s anything I can do to lower that noise floor. My hope is that the CPU or display may simply need better grounding or isolation. My time is limited at the moment, but I will open into this radio in the next few weeks.

In fact, eventually completing the kit build will give me an opportunity to explore the components and connections in much better detail.

I do know that my unit also seems to have the power output issue that some of the roWaves kits have. I can’t achieve anything better than 3.25 or 3.5 watts output at 13.8 volts. It should be about 5 watts at 13.8 V.

I would welcome your suggestions especially if you’ve built the (tr)uSDX kit or if you’ve put your assembled (tr)uSDX on the air and found that it had much better audio characteristics.