Many thanks to Pete (WB9FLW) who shares the following article by Bob (KD8CGH) regarding the uSDX transceiver kit.
I reached out to Bob who has kindly given me permission to share his article on QRPer:
An Introduction to the uSDX
by Bob Benedict (KD8CGH)
There is a new open source, home brew multi band, multi mode QRP transceiver that grew out of the QRP Labs QCX. Through some serious wizardry it retains an efficient class E RF amplifier for SSB and digital modes. It crams impressive SDR capabilities into an Arduino.
This has an interesting international development process conducted on https://groups.io/g/ucx/topics with contributions by many, including the usual gang of suspects: Hans Summers G0UPL, Guido Ten Dolle PE1NN, Barbaros Asuroglu WB2CBA , Manuel Klaerig DL2MAN, Kees Talen K5BCQ, Allison Parent KB1GMX, Jean-Marie T’Jaeckx ON7EN, Ashhar Farhan VU2ESE, and Miguel Angelo Bartie PY2OHH. I apologize to the many others whose names I didn’t list. A summary is in the WIKI https://groups.io/g/ucx/wiki.
The basic work uSDX appears to have been accomplished by Guido Ten Dolle PE1NNZ. It uses pulse width modulation of the PA supply voltage to transmit modes other than CW while retaining class E efficiency and uses a direct conversion SDR receiver.
The basic idea behind Class E nonlinear amplifiers is that transistors have little loss when they are switched fully on or off. The losses occur when devices are limiting power flow in linear amplifiers. The idea behind a Class E amplifier is to use transistors in a switching mode to generate a square wave to drive a resonant circuit to generate RF power.
This method is used in the popular QCX QRP CW transceiver kit line developed by Hans Summers and sold through QRP Labs https://qrp-labs.com/. More than 10,000 of these great transceiver kits have been sold (I built one). There is a good discussion of the circuit and particularly of the class E amplifier in the excellent QCX documentation https://www.qrp-labs.com/images/qcx/assembly_A4-Rev-5e.pdf.
The QCX was the base for the QCX-SSB which starts with a QCX and modified the circuit and software to add SSB capabilities. The wizardry that Guido accomplished uses pulse width modulation of the PA supply voltage to control the amplifier in an Envelope Elimination and Restoration (EER) technique https://core.ac.uk/download/pdf/148657773.pdf. To generate SSB a DSP algorithm samples the audio input and performs a Hilbert transformation to determine the phase and amplitude of the complex signal. The phase changes are transformed into temporary frequency changes which are sent to the clock generator. This result in phase changes on the SSB carrier signal and delivers a SSB-signal with the opposite side-band components is attenuated.
On the receive side a direct conversion SDR receiver is used with the I and Q signal digitized and all further processing carrying out digitally. Attenuators are included to help not overload the ADC range. Documentation is at https://github.com/threeme3/QCX-SSB . In addition to a good description of the theory and hardware mod there is also a good description of the software command menu.
From there development took off in several directions. One is by Barbaros Asuroglu WB2CBA and Antrak that uses through hole components (mostly) and replaceable band boards that hold the low pass filter and band dependent class E amplifier components (an inductor and capacitor). Barb also includes boards designed to be a case top and bottom, battery pack and a PA.
I built the variant designed by Barbaros Asuroglu WB2CBA and I’m pleased with it’s performance. I ordered 10 main boards and 40 LP filter band boards PCBs from PCBWAY, but now you can also purchase single boards sets from https://shop.offline.systems/.
In an example of hams collaborating at its finest, Hans Summers announced on 9/11/2020 that his new QCX mini product, a QCX in a smaller package, will include a daughter board that can be used to give the QCX mini a uSDX like SSB capability. The QCX mini has the same circuit as the QCX but uses SMD components packaged it into a two board stack that is less than half the volume of the original QCX. The mod is unsupported by QRP-LABS but may be supported by the uSDX group.
The following article was originally posted on my other radio blog, the SWLing Post.
Earlier this year I published what I called an “initial” review of the CommRadio CTX-10 QRP transceiver, promising an eventual final review. The reason for this is that I sensed there were important CTX-10 updates on the horizon, and I wanted to re-evaluate the rig once the upgrades had been implemented through firmware.
I’ve been very pleased with the attention CommRadio has paid to their customer feedback on some of the most important requests.
Instead of reiterating what I wrote in the initial review, I’ll jump straight into the upgrades.
At time of posting my initial review, the CTX-10 didn’t have A/B VFOs. This was my primary gripe about the CTX-10, because without A/B VFOs, there was no way to operate split, which meant that you could not work DX stations that use split to manage large pileups. This is actually a really important feature for a QRP radio because during split operation, a pileup is pulled apart across a few kHz of bandwidth, thus giving a 10-watt signal a better chance of being heard through a collection of legal-limit signals.
On June 10, 2019, CommRadio released a firmware package that added A/B VFOs and the ability to operate split to the CTX-10.
Even though there are only a limited number of buttons on the front panel, it’s incredibly simple to enter into split mode:
Chose the frequency and mode;
Hold the STEP button for one second or more, then release. You’ll then see a split display indicating the TX and RX frequencies.
Use the left arrow key [<] to toggle between them.
I do like the clear TX and RX lines, which leave no doubt in the user’s mind what the frequency used for transmitting and receiving is. On some radios, this can be a bit confusing.
Split operation is simple and effective, thus I consider this issue fully resolved.
In my initial review, I noted that the CTX-10 ATU needed near-resonant antennas for the ATU to make a strong 1:1 match. Indeed, a number of times I actually used a near-resonant antenna in the field––the EFT Trail-Friendly, for example––and the ATU couldn’t get below a 3:1 match. For what it’s worth, CommRadio states that the CTX-10 can easily handle 3:1.
CommRadio has made modifications to the ATU function, improving the performance of the antenna-tuner algorithm, which had a significant impact on 80 and 60 meters. I’ve also had better luck with a number of field antennas I’ve tried on 40 and 20 meters. Is it as good as the Elecraft KX-series ATUs? No, but I consider those ATUs to be some of the most flexible on the market.
Having a built-in ATU on the CTX-10 is certainly a valuable feature in the field. When I need to match a challenging antenna with the CTX-10, I bring my Emtech ZM-2 manual tuner along for the ride. A perfect combo.
There still is no way to adjust the microphone gain control nor microphone compression on the CTX-10. Much like a military or commercial radio, the CTX-10 is optimized for just one style of mic: in its case, the modular MFJ-290MY or Yaesu MH-31A8J handheld mic.
The CTX-10 microphone input has a limiting pre-amplifier with built-in compressor and ambient noise gate–in short, the CTX-10 handles all microphone settings automatically.
Through firmware updates, a number of positive adjustments have been made to the microphone settings:
the microphone-decay timer has been tweaked so that audio clipping is less of a concern
audio clarity and gain have been improved
audio power has been improved resulting in .5 to .75 watts of additional peak power
microphone audio leveling has been improved
VOX attack and decay timing has been improved
These are all welcome adjustments.
I would note here, though, that if you plan to use a mic other than the MFJ-290MY or Yaesu MH-31A8J handheld mics, you will have a limited means of adjusting the mic parameters unless you have an external mic EQ. A number of readers, for example, have asked about using their Heil boom headset with the AD-1-YM cable adapter on the CTX-10. Boom headsets are a wonderful tool for field operation because they free your hands to log contacts. As for using boom headsets on the CTX-10, since I don’t have the appropriate adapter, I can’t speak to this. But since you can’t control mic gain, it might take time to learn how to position the boom mic and adjust your voice level for optimum performance.
As mentioned in our initial review, the CTX-10 does not support QSK/full break-in operation. Rather, the CTX-10 uses a traditional relay for switching between transmit and receive. During CW operations, you’ll hear a faint relay click when switching from TX to RX and back again.
This isn’t a problem for me, as I rarely set my CW rigs for full break-in, but the CW hang time delay on the CTX-10 is not currently adjustable. For high-speed CW ops that prefer a faster relay recovery, I suspect this could be an annoyance.
There have been recent CTX-10 firmware upgrades that have helped solve issues found with CW keyer timing in early units. I found the timing issues were mainly present while sending high-speed CW (25 WPM+). My buddy Vlado (N3CZ) put the CTX-10 through some high speed tests, and was pleased with the results overall.
I will reiterate here that the CTX-10 lacks other controls many CW operators appreciate. Currently, the CTX-10 lacks a sidetone control; as a result, you cannot change the sidetone volume/tone, nor can you turn it off. I continue to hope that CommRadio will fix this quirk via a future firmware upgrade.
The CTX-10’s built-in CW keyer does not currently support iambic keying. Meaning, when both levers of a dual paddle are closed simultaneously (squeezed), it will not send a series of alternating dots and dashes. I imagine this could be addressed in a future firmware update.
Additionally, without re-wiring your paddle, you can’t change which side of your paddle sends ‘dits’ and which sends ‘dahs.’ A minor con, for sure–still, most modern QRP transceivers allow you this flexibility.
All in all, the CTX-10 will serve the CW operator much like a military set in field operations. True, I wish it had a few more adjustments, but it has all of the basics, and I’ve received several great reports regarding signal and tone.
Revisiting the basic feature set
Let’s be clear: as I stated at length in my initial review, the CommRadio CTX-10 was designed around simple operation, like one might expect from a military or commercial channelized radio. I know ham radio operators and preparedness enthusiasts who prefer this approach to gear design, and they will appreciate this CTX-10 design philosophy.
Still, the CTX-10 lacks many of the features and adjustments you’d typically find on a QRP transceiver in its price class. Instead, the CTX-10 was designed to handle many of these adjustments automatically.
The CTX-10 still has no separate RF gain control. The CTX-10’s RF gain is directly tied to the three AGC settings (slow, medium, and fast). While I believe it does a fine job of adjusting RF gain, I do ride an RF gain control a lot during noisy summer conditions, and miss this feature.
The CTX-10 still has no passband (PBT) control, notch filter, or noise blanker––all features I’d normally expect in a QRP radio at this price level.
There are no CW (os SSB) memory keyers. I wouldn’t expect these, as I believe only the Elecraft KX2 and KX3 sport this feature in this price class of QRP radios.
Please note: some of these features could potentially be added in future firmware upgrades. If one of these items is keeping you from purchasing the CTX-10, please contact CommRadio and inquire.
Is the CTX-10 for you?
With the most recent upgrades, CommRadio has solved the major issues that kept me from heartily recommending it in my initial review.
The addition of split operation was especially key for me, as I do operate split. The more nuanced adjustments to the CW keyer, an extra feature to prevent the radio from accidentally turning on while in transit, and the adjustments to the mic algorithm, all make this radio more pleasant to operate at home or (especially) in the field.
As I mentioned in the initial review, the CTX-10 owner is one who values a very simple, straightforward radio. Perhaps someone who began operating in a commercial, military, or aviation field, and/or who likes the “get on and get the job done” approach. Someone more interested in making contacts than in radio operations and refinements. Those who want a sturdy, lasting, no-frills, set-it-and-forget-it rig. If that’s you, take a closer look at the CTX-10: it may just suit your needs to a T.
If, however, you’re looking for a full-featured QRP radio with many of the features and nuanced adjustments you’d expect in the shack, check out the Yaesu FT-818, Elecraft KX2, or Elecraft KX3. All of these excellent rigs are time-tested and very flexible.
The two major advantages of the CTX-10 over competitors are:
the ability to charge the internal batteries from almost any voltage source, and
a higher TX duty cycle (without needing to add external heat sinks).
I believe the CTX-10 will have strong appeal for radio enthusiasts who value these characteristics:
All-in-one-box portability with no extra wired accessory components
Best-in-class internal battery life
Best-in-class intelligent battery charging
Digital modes like FT-8 and the ability to operate them in the field from internal batteries for extended periods of time
The equivalent of a simple portable military/commercial set
A well-balanced receiver with few manual adjustments
Broadcast listening, as the CTX-10 is also superb broadcast receiver
The CTX-10’s overall construction and components are, as I’ve said, near mil-spec. While the CTX-10 isn’t weatherized or waterproof––no more than any of its current competitors––the construction is top-shelf, for sure. It should run for decades without need of repair.
The CTX-10 is built like a tank, and has excellent receiver characteristics for field operation. It’s also designed and manufactured right here in the USA. All the better.
(Note: This is a cross-post from my other radio blog, the SWLing Post.)
So the ALT-512 QRP SDR transceiver has landed at SWLing Post HQ. This little rig is on loan from Aerial-51 and I’ll be spending the next month or so putting it through the paces.
I can already tell that the ALT-512 has some strong points:
It’s incredibly portable and easy to take to the field, providing you have a battery and resonant antenna (or external ATU).
The color backlit display is quite readable at any angle despite being rather information-dense.
I really like the waterfall display. It’s large enough to be quite useful.
The ALT-512 can connect directly to your computer for digital modes like FT-8. No external sound card needed.
The menu system contains a wide array of features and options for granular tweaks and modifications.
The ALT-512 includes the European 4 meter band.
Although I prefer using headphones with small radios, the ALT-512’s small internal speaker does a fine job.
Rob Sherwood tested the ALT-512 (indeed, this very unit) recently and added it to his receiver test data. It performed quite well especially considering the price.
Any negatives so far? Nothing major:
No internal ATU or battery options. At this price point (799 EUR), I wouldn’t expect either of these.
The ALT-512 is not general coverage. This is a negative for those of us who like SWLing, but a positive for ham radio use as the ALT-512 sports band-specific bandpass filters to reject out-of-band strong stations. You can tune to some stations above the 40M band and also the full mediumwave band and below (down to 100 kHz), although I wouldn’t expect stellar performance in those regions.
So far, I’m very pleased with the ALT-512’s performance.
Next, I’ll be taking it to the field and see how easily I can activate a few POTA (Parks On The Air) sites! Stay tuned!
For someone, like me, who loves playing radio in the field (Parks On The Air and Summits On The Air) this looks like an ideal rig. It’s one of the only ham radio transceivers I’ve seen that is weatherized to some degree (how much, we don’t know yet).
I don’t see a speaker on the TX-500, so I’m guessing it might require a mic/speaker combo or an external speaker of some sort? I also don’t see a built-in ATU, but at $700, I certainly wouldn’t expect one.
With a power consumption of 110 milliamps at 13.8 VDC, this little transceiver should run for ages on a modest battery pack.
This is certainly a fascinating prototype QRP transceiver. If the Discovery TX-500 transceiver can be produced and marketed at $700 with all of the features mentioned so far, it should certainly fly off the shelves. They can certainly take my money!
Of course, I will plan to grab one of these for review. I’m also eager to see how this little SDR transceiver might perform on the broadcast bands.
We will post post TX-500 updates and details as they become available. Bookmark the tag Discovery TX-500 and stay tuned!
At first glance, you’ll see a similarity between the ALT-512 and the LnR Precision LD-11/Aerial-51 SKY-SDR. The LD-11 and SKY-SDR, are very similar, save the LD-11 is marketed to North America (via LnR) and the SKY-SDR to Europe. The SKY-SDR had several iterative upgrades, most importantly the dual-threaded software used in the firmware, which cut CPU latency in half. Both the LD-11, SKY-SDR and now the ALT-512 are made in Europe.
Many thanks to Pete (WB9FLW) who shares the following information regarding HobbyPCB’s much-anticipated portable transceiver which is now shipping. The price is a competitive $529.00.
The following information comes from the HobbyPCB website:
The IQ32 is 5W output, 80-10M Amateur Radio transceiver with powerful 32 bit processing providing high-end features at an entry level price. The IQ32’s 3.2″ color LCD touch-screen display and dual control knobs provide an enjoyable operating experience in a robust package.
Available for immediate delivery!
Introducing the HobbyPCB IQ32 HF transceiver, based on the high performance RS-HFIQ RF system, the receiver in the IQ32 consists of 5 band-pass filters to reject out-of-band signals, an LNA with frequency dependent gain and a conventional quadrature down-converter. The transmitter features a Class A, 5W power amplifier with individual low-pass filters for each band to exceed FCC requirements for spectral purity.
The IQ32 features a large, color, touch-screen display providing an enhanced user interface and informative spectrum and waterfall displays found on radios costing much more. With a powerful STM-32 DSP processor, the IQ32 transceiver has variable filtering, multi-mode AGC, memory functions, built-in PSK encode/decode with keyboard support.
5W not enough power? Add a HARDROCK-50 to your station to boost up to 50W. The IQ32 and HARDROCK-50 seamlessly integrate together for a powerful mobile/base station!
Simple upgradeable firmware, no connection to a computer required, no drivers, no cables. Simply insert a thumb-drive with the appropriate file and the IQ32 updates its own firmware.
Frequency Range: 3-30MHz (performance guaranteed on 80/60/40/30/20/17/15/12/10M ham bands)
Sensitivity: MDS < -128 dBm on 80M dropping to < -135 on 10M
I may see about grabbing an IQ-32 to evaluate. I’m very curious how its receiver might stack up to the Elecraft KX2, the CommRadio CTX-10 and the LnR Precision LD-11. (Please note that these links lead to my other radio site, the SWLing Post.)
It doesn’t appear that the IQ-32 has an AM mode, but I would still like to see how it might handle broadcast listening on the shortwave meter bands using ECSS.
Check out WA2EUJ’s IQ-32 presentation at the 2018 Hamvention on YouTube:
Many thanks to Pete Eaton (WB9FLW) who shares the following post:
Last March Ashhar Farhan VU2ESE the designer of the very popular BITX20 and BITX40 series of mono-band HF Transceivers announced a new low cost Rig called the uBITX (micro BITX) a full blown 80-10m 10 Watt SSB/CW Transceiver. Now comes word that after many months of very hard development work by Ashhar this much anticipated Rig will soon be available.
For those not familiar with the Project this is *not* a kit, rather like its sibling (the BITX40) it consists of two assembled and tested Circuit Boards. The RF board measures 5.5 x 6 inches and a second small plug in daughter card that takes care of the digital portion of the design including the 2X16 LCD, Arduino Nano, and Si5351 which are used in the VFO. Add a Cabinet, Knobs, and Connectors and you have a full blown HF Rig. An added plus is that except for the Gerber PCB files everything else (including the firmware) is Open Sourced!
When I heard from friends that Ten-Tec had announced two new QRP transceivers at FDiM, I almost fell out of my seat. I’ve heard very little in the way of QRP coming out of Sevierville since the sad news of them dropping the popular/legendary Argonaut series.
Then, this week, when they announced the news on their (new) website, I got even more excited–these transceivers are field portable and small! They very much resemble my Elecraft KX-1.
The new rigs come in two flavors:
The R4030 covers the 40 and 30 Meter ham bands
The R4020 covers the 40 and 20 Meter ham bands
The news, which started with a gasp, though ended with a sigh as many noted that these rigs closely resembled the HB-1A (Made In China) QRP Radio. Could this be? It was a little hard for me to imagine. Being a serious Ten-Tec fan, I hang my hat on the fact that my TT radios are designed and made locally–within a 2 hour drive of my QTH! I didn’t want to hear any more rumors, I needed to know from the horse’s mouth, so I emailed TT sales–they responded:
Yes, the R4020 and R4030 is based off the HB-1A transceiver with some minor modifications. We are the exclusive dealer for the R4020/4030 and will warranty and sell this item from our office in Sevierville, TN. We will offer a 1 year full replacement warranty.
So, it was true–I was not shocked. Why? The price of the R4020/R4030 is only $249. That’s an incredibly low price for a Ten-Tec item. Too low.
I’m not sure what the “minor” modifications are that Ten-Tec made, but I imagine they had to bring it up to FCC compliance and perhaps tweak the receiver a bit. We’ll soon see.
I realized, this morning, that I simply need to forgive Ten-Tec for doing this. I love their equipment and hold their company and employees in the highest regard. I can’t blame them for outsourcing a radio–why?
This is a tough economy. I’ve been worried about our domestic manufacturers like Ten-Tec and Elecraft (though, surprisingly, Elecraft actually upgraded and moved their production to a larger facility). I’m surprised that they’re able to hang on. I suspect Ten-Tec has had to lean on their other markets (government, enclosures, etc.) to support the amateur radio side of their business.
Ten-Tec could probably not put 2009/2010 resources into developing a radio on their own when they had low-hanging fruit, like the HB-1A, just waiting to be brought to the USA (officially). R&D is not cheap–even if it’s in-house.
They are servicing this radio in Sevierville, TN. That makes me feel a lot better about about buying one of these transceivers. Ten-Tec service is top-shelf!
They really needed to bring QRP back into their non-kit product line.
Bottom line? I’ll probably get one of these and try it (well, after I invest in a nice vintage boat-anchor set up). I’m in no hurry as I have an Elecraft KX1 and it is my favorite QRP radio.
I will post reviews of the new TT radios as they become available (contact me if you have one). In the meantime, I’ve included some useful resource links below.