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.

In fact, I’ve had so many questions about this little radio, that I took the unusual step of pushing this field report and video to the front of the line. (I’m currently a good 3-4 weeks behind posting my field reports.)

I also published a report of my initial impressions of the (tr)uSDX on Friday while waiting for the video to upload.

If you’re considering the (tr)uSDX, I’d encourage you to read my previous post as I won’t repeat many of the points I made in the previous article.

South Mountains State Park (K-2753)

Since I was very limited in terms of time, I chose South Mountains State Park as my POTA site. The Clear Creek access is only a 20 minute detour during my weekly travels and it has all of the ingredients for an easy POTA activation: a picnic table, huge tree, and it’s usually very calm there with much less foot traffic than other parts of the park.

I packed the (tr)uSDX in my Spec-Ops SOTA pack where I actually had quite a bit of extra gear. I hadn’t had a chance yet to put together a dedicated field kit for the (tr)uSDX, so having extras along for the ride was a good idea.



Setup was simple. First thing I did was deploy an end-fed half-wave that Steve (MW0SAW) sent me. (Thank you, Steve!) This is an antenna he built at home and sent to me as a gift–it’s not commercially available. It’s a great design and I love the winder! I’ve now used this antenna on a number of activations.

Being a 40 meter EFHW, I planned to activate using both the 40 and 20 meter bands.

Next, I set up the (tr)uSDX.

I connected the (tr)uSDX to my EFHW via a 20′ long RG-316 BNC to BNC feedline. For power, I connected the rig to my 3Ah 12V LiFePo4 Bioenno battery.

The built-in speaker simply isn’t loud enough for my action camera to pick up the audio, so I connected my Sony digital recorder to the headphone jack.

The audio, I should mention, is possibly the biggest con with my particular (tr)uSDX unit. It’s harsh and difficult to control.

The volume level is controlled on a scale from 1 to 16. I need to keep it set as high as 11 or 12 to hear signals. If I go below 11, the signals disappear and, oddly, the noise floor increases. If I move above volume level 13, the audio can produce a constant squeal. I demo this at the end of the video.

I will tinker with the audio settings over the coming days and also look inside to see if there’s some way to lower the noise floor even a tad. Perhaps a little extra grounding can help?

In my activation video below, I lowered the volume in post-production to make it more tolerable. I added notes in the video to indicate when I lowered the audio level.

On the air

Because I tested the radio in advance, I knew I would achieve about 3 watts of output power with my 13.2 volt battery. This is lower than the advertised 5 watts, but I already know how to fix this, I believe.

I started calling CQ POTA on the 40 meter band.

WB1LLY was my first contact and his signal was incredibly strong!

Next, I worked K8RAT and nine more contacts all within a span of about 15 minutes for a total of 11 contacts logged.

Next, I tried moving to the SSB portion of the band to work some P2P stations. Unfortunately, none of them worked out. Turns out, band conditions were also in the dumps that day.

Here’s my full log sheet:


Here’s how this 40 meter, three watt activation looks on a map:

Activation video

Of course, here’s my real-time, real-life video of the entire activation. As always, there are no ads, no sponsorships, or anything else; just a real video, blemishes and all.

This video is slightly different than the average. As I mentioned above, the audio is definitely less refined than it would typically be. I had to work with the limited audio gain I had on the (tr)uSDX. Also, I do speak at length about the (tr)uSDX before and after the activation–feel free to skip over that if you like (I include chapters to make that easy).

Click here to view on YouTube.

A work in progress!

While this initial experience with the (tr)uSDX wasn’t stellar, that little sub $150 radio did bag me an activation in pretty short order.

Since publishing my initial impressions, I’ve gotten a lot of advice about calibrating the frequency display, increasing the power output, and even mitigating a bit of the noise through the DNR functionality.

I will certainly see if any mod can be done that shed some of that internally-generated noise. As I said, I feel like grounding in the right place could really help.

Thank you!

Thanks for joining me on this activation!

As always, I’d like to send a special thanks to those of you who have been supporting the site and channel through Patreon and the Coffee Fund. While certainly not a requirement as my content will always be free, I really appreciate the support. It makes videos and reports like this one possible.

If you have a (tr)uSDX and have any advice for me, I very much welcome it. As I said numerous times in this video: this is a project and experimenter’s radio. I never expected it to perform like an IC-705 or KX3! I do, however, believe there are things I can do to enhance its performance and I look forward to playing with it on the workbench!

Have a wonderful week everyone–I hope you’re able to make some time for a little radio!

72 de Thomas (K4SWL)

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

  1. Hi Thomas
    If you use an external activ speaker you’ll be surprised how different this little setup sounds. You still have to play with the loudness settings of the truSDX. I think, there is no other way to improve the sound quality besides just using headphones, at least I have not found one.
    73 and good luck with your new toy
    Gerald – HB9CEY

    1. Thanks, Gerald,

      I will give this a go. I have an excellent Sony speaker that might even help mitigate some of the higher frequency hiss in the audio amplification chain.


  2. Really enjoyed this write up and the video.

    I did a little more testing with my own (tr)uSDX and after the previous test when I found that higher impedance headphones sounded nicer & cut a lot of the noise from the audio circuitry, I tried out a cheap little in-line 3.5mm patch lead with a volume potentiometer and a normal set of earphones.

    To my ears, it’s a huge improvement, volume on the radio can be set somewhere comfortable (say between 9-11) while you can dial the potentiometer back, such that it cuts the worst of the audio noise, while allowing a pretty nice radio signal through. So I’d suggest people try it out – the little patch leads are very cheap and are useful with the likes of the MTR3B too.

    Regarding the speaker audio, I believe the speaker was added late in development as a simple backup, in case a person forgot/lost/broke their headphones/external speaker – and for that it works, it’s brilliant to have in a pinch and could save a POTA/SOTA activation, but it will never deliver an ideal audio experience.

  3. I built this radio this week. I am very happy with it. I got over 5 watts on all 5 bands. All bands are with spec for output. I only had to tweek the 80 meter coil to get over 80% efficiency. For the size of the radio the feature set is great. I made over a dozen SSB contacts and all the audio reports were fantastic. It has a few quirks, it does not save the freq you were last on when you change bands. The NR setting is not saved and must be set every time. The filters are fantastic. I did have to adjust the frequency a bit, but there is a menu item for that, you just need a freq counter or you can use WWV.

    I would buy this radio again, and not think twice about it. In fact I am probably going to buy another and build it for 10,20,30,40,80.

    73 KB9JJA

  4. Evening Thomas
    My (tr)uSDX transceiver arrived from China today — from the ‘approved’ supplier.
    I must say I’m impressed — a bit more so than you are with yours.
    It has a full 5+ watts out on all the bands I’ve tested so far, the CW RX filtering is really good — as it the built in decoder.
    The filter bandwidths for SSB and CW are good and all in all I think its amazing — for £129 delivered to my door!

    I’ll do a full review once I’ve got to grips with the little beast.

    An assessment you made I will agree with is the audio through the internal speaker is a bit naff and I think causes mechanical acoustic feedback when you turn it up ‘beyond 11’

    I’ll try some QSOs tomorrow.

  5. I just finished the do it yourself version(had to wind 13 coils) and couldn’t wait to tune. My first contact was england. I got only about 70% efficiency but 5+ watts on 80, 40, 20. Had to tweek coils to get the second harmonic down, but so much fun. I use regular head phones instead of speaker, but the maker of this suggests using the small speaker. My only complaint is that sometimes it hard to get it out of a particular mode back to frequency. Thanks for turning me on to this radio!

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