uSDR+ QRP software defined radio review

I’m taking out this inexpensive kit radio for a spin, and it’s been exceeding my expectations so far

Published in

N2RAC | DU2XXR Amateur Radio and Communications

7 min readDec 25, 2023

For this Christmas, my ham son and daughters pitched in to get me a pre-owned uSDR+ radio, which cost PhP 4,000 or the equivalent of $72, and it’s been exceeding my expectations, so far. The Seller even included a free QRP guys endfed antenna un-un (which I believe is not the original one but a copy, but should work OK nonetheless). This still sells for around PhP 8,000 new or around $145. A quick search on Amazon got me this radio for $138. You may also find official sellers of the latest (tr)uSDX here.

I was quite sad to have to put up my mobile all-bander radio for sale, so this would be a good alternative for the occasional portable and even mobile HF operations.

Note that this is one of the derivatives/clones of the open-source USDX radio, and while the creators of the original project have expressed their disapproval of the numerous unofficial builds due to profiteering and differences in quality, I have decided to graciously accept this item and share my experiences with it with fellow hams.

Some details and observations:

HF bands 80, 40, 20, 15, 10 meter; power output and receiver capability will depend on the band and frequency used.
Can do up to 10 watts, usually 5 watts on battery power. User will need to make adjustments to the PA bias and maximum output to achieve the best SSB modulation.
Has an internal battery (not sure of the size and capacity, but will know for sure when I get to use it in mobile operations). The radio has a switch that lets you choose between operating on battery power or on external power. Separate connectors for battery charging and external power, too.
I have tried operating with different PA (power amplifier) max settings. Got 5 watts at 160 setting and 8–10 watts on the 240 setting (maximum of 255). Other reviewers have found that a PA minimum bias of 10 and max of 160 resulted in the best audio output with no distortion. I get 5 watts of output from a 160 PA maximum setting, which should be enough for QRP operations. Having access to 10 watts is a good option, for as long as it does not result in distorted audio.
CW, LSB and USB modes. Modes can easily be toggled with the MODE button.
Several filter options for receive: bandwidth, two different types of attenuation. I believe ATT1 is similar to RF gain, while ATT2 is mostly audio gain or attenuation on a different stage. I have yet to find more documentation on this. Double-pressing on the mode button adjusts bandwidth. Long-pressing on the mode button gives quick acces to RIT.
Receiver performance is acceptable for an inexpensive radio. In my experience, it’s similar to the Xiegu G90, with the exception that the filters are limited to bandwidth, attenuation, and incremental tuning, as well as some form of noise reduction. There are no filters for IF shift, notch filter, etc. With some playing around, you might be able to minimize the noise for reduced operator fatigue. But don’t expect much.
Receiver performance is siginificantly lower than my Yaesu FT991A, especially when working weak stations (the 991A in itself not such a great performer in that regard). But given its portability it is an acceptable compromise.
There’s an internal power meter and SWR meter. The power meter is not very accurate, although it gives some indication of the output power per band. On the 40 meter band, internal meter shows 5 Watts, but I’ve measured output to be at 8 to 10 Watts with PA setting of 240.
Has two(!) built in PTT buttons. Also has a built-in mic so you can operate it hand-held, which helps reduce gear you bring for portable operations. I found that the hand mic that was included in the package has been useless, delivering weak audio! I therefore prefer using the uSDR with its built-in mic.
It lacks a scope/waterfall and built-in antenna tuner like some newer SDRs, particularly those Chinese-designed Xiegu radios. But for its price, it’s a great value radio. This pre-owned unit costs just around 1/20 of a new Icom IC-705 or around a fifth of a new Xiegu G90 or the Xiegu X6100. I used to have a G90, which I bought and sold for PhP 25,000 (around $450), and while that had great value for a 20-watt radio with built in ATU, the cheaper USDR provides a lower point-of-entry for hams or at least a lower price point for those wanting to play around with portable SDRs.

Additional observations

Edit 2023–12–25 1300H: There is an adjustable audio drive level, which I believe is the compression level. I’ve set this to 4 with OK results. Reviewers have said that their audio starts to get distorted at 5 and up.
Edit 2023–12–25 1300H: At 13.8V, current draw at receive/standby is at 0.1A. Transmitting with a PA max setting at 240 (outputting 8 watts on 40 meter band), the current draw is at 1A.
Edit 2023–12–25 1800H: The radio does not have a voltage indicator, so if you’re using battery power, battery status is a guessing game. From reviews I’ve read, though, the radio has a long battery life. Some report having a 6Ah battery. With the current draw indicated above, you will probably get 60 hours of SWL time, or around 20 hours of 80% standby and 20% transmit.
The power and SWR meter are only displayed at CW transmit. This can also be selected as voltage meters, but I’m not sure exactly what voltage is being measured.
Edit 2023–12–28: As per QRZ reviews, older firmware versions basically made this transceiver useless. Version 4+ significantly improved the functionality and usability. The transceiver I have uses version 4.01. Firmware updating isn’t exactly easy, though.

The takeaway

Overall, it’s a good value radio for its price. I may have been lucky with receiving an assmbled unit that does not have issues like what others report. I was also able to measure 8–10 watts output (depending on band) even on internal battery power. I’ve mostly tested it on my home setup with my end-fed halfwave, but I shall be testing it in the field on portable ops soon.

The kit is available for order as a DIY project from https://dl2man.de/ . China manufacturers also have their own clones, so just a caveat for potential buyers. YMMV for these unofficial radios. You might also see different variations and form factors, with different screen and button placement. Some even don’t have built-in batteries. Some reviewers have complained of weak transmit audio, but you can play around with the PA max and PA bias settings, as well as drive settings to achieve your ideal modulation.

Am I recommending this radio? If it’s your first time getting on HF, you might find it lacking, and you might be disappointed with the user experience. But if you already have a rig and want some portable radio you can bring out in the field and not worry about the cost, then this one can be a good option. Agadin, YMMV with assembled kits that are not from official sources. The (tr)uSDX will most likely be a better radio than unofficial ones!

Update 2024–02–21: I was able to make my first DX contacts on this portable radio and antenna. I had QSOs with HL4CDA in Seo Gwi Po City, South Korea (~2,000Km) and YE8UI in Koto Gorontalo, Indonesia (~1,500Km) on the 40 meter band. It helps that propagation is good this particular evening.

Update 2024–02–27: Happy to report a new DX contact with the USDR+ with JJ0WON in Nagano, Japan around 3,000 Km away. He received me 3x5, while I received his 100 Watts signal at 5x7 on the 20-meter band.

QSO with HL4CDA in South Korea