Tag Archives: Pete (WB9FLW)

An Introduction to the uSDX transceiver kit

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.

Another development track by Manuel Klaerig DL2MAN uses SMT components in a stacked board layout and has a relay switched band pass board https://groups.io/g/ucx/message/1596  and  https://groups.io/g/ucx/files/DL2MAN uSDX-Sandwich Files. A new revision has been released that uses serial resonance class E amp design and easier to obtain relays, https://groups.io/g/ucx/files/DL2MAN uSDX-Sandwich Files with new Serial Resonance Class E Multiband Circuit .

Other development streams include one by Kees Talen K5BCQ https://groups.io/g/ucx/files/K5BCQ uSDX Board Schematics and Jean-Marie T’Jaeckx ON7EN https://groups.io/g/ucx/files/QCXV4.zip.

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/.

I also designed and 3D printed a case for the transceiver and a small box to carry band boards. Info at https://www.thingiverse.com/thing:4582865 and at https://www.thingiverse.com/thing:4587868 and also in the files section https://groups.io/g/ucx/files/3D printed case for Barb WB2CBA V1.02.

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.


More information at https://groups.io/g/ucx/topics and don’t forget the WIKI https://groups.io/g/ucx/wiki.


Bob,  KD8CGH

Many thanks again, Bob, for sharing this excellent uSDX introduction. Thanks again for the tip, Pete!

Pete also notes that there is a very active uSDX experimenters discussion group on Groups.io with over 100 members: https://groups.io/g/ucx

W9FKC’s suitcase portable

Many thanks to Pete (WB9FLW), who writes:

Found this link on the Soldersmoke Blog this morning.

Click to access W9FKC.pdf

Interesting to compare this 70 year old Rig with your KX2 or KX3!

We’ve come a long way since then.

Indeed we have, Pete! But, man oh man! What a gorgeous vintage portable–absolutely beautiful vintage example of form following function!

Click here to download the PDF.

Experimental Methods in RF Design (Classic Reprint Edition) $20 closeout price via the ARRL!

Many thanks to QRPer, Pete (WB9FLW), who writes:

Get it while you can (Classic Edition) includes CD-ROM PDF Files for Solid State Design and Introduction to RF Design.

Closeout Price $20!

Very sad to see this go,even if you own a copy buy a spare!

Click here to order your copy at the ARRL.

Thank you for the tip, Pete!

QRP Labs new QCX+ QRP CW/WSPR transceiver kit

Many thanks to Pete (WB9FLW) who writes:

Hi Thomas,

QRP Labs has just announced the QCX+ which as the name implies is an upgraded version of the very popular QCX line of transceivers

To date almost 10,000 kits have been sold, here’s a brief overview of the the differences and new features made to this popular Transceiver.

The QCX+ is the almost same circuit as the QCX, with two very minor changes. QCX+ runs the same firmware as QCX, and has identical operational and performance characteristics. QCX/QCX+ firmware will always be compatible with both the QCX and QCX+. The evolution of QCX to QCX+ provides several improved features in physical layout, as follows:

1) Physical layout of controls and connectors

2) Optional enclosure

3) Additional and changed connectors

4) More spacious PCB, more than double the board area, with less densely packed components, and more test/modification points

5) Improved heatsinking

6) Three minor circuit changes

7) No microswitch key

Price has gone up slightly to $55, still no other QRP Transceiver on the market today comes close to the features offered by the QCX+ at this price point.

More Info:


Thank you so much Pete! You’re an enabler! Since I’m not at Hamvention right now, those radio bucks are burning a hole in my pocket. The QCX+ looks like a fun transceiver to build! Thanks for the tip.

Icom IC-705 demo and pricing

Many thanks to QRPer, Pete (WB9FLW), who shares the following sneak peek video of the new IC-705 transceiver from Amateur Logic TV with guest Ray Novak from Icom America:

Pete also notes that Ham Radio Outlet’s price has been announced a the 2020 Orlando Hamcation. According to two members of the group, the pre-order price at Hamcation is $1,175 US–the price will increase $100 after Hamcation.

Availability is still unknown: retailers and Icom have not committed to firm delivery date yet other than noting it will be sometime in 2020.

Thanks, again, Pete for the tip!

uBITX v6 QRP transceiver now available for $150/$199 US

Many thanks to QRPer, Pete (WB9FLW), who notes that Ashhar Farhan (VU2ESE) has recently announced the availability of the uBITX v 6.0–as Pete notes, “just in time for the Holidays!

Pete shared the following message from Farhan:

Here is what [the uBITx v 6.0] looks like :

And of course, you can buy it on hfsignals.com. The shipping will happen from Tuesday onwards. We have a limited supply of the first 200 boards. The rest is for after Christmas.

The most important thing about this revision is that the Radio circuitry is almost unchanged. We have incorporated the connectors on the PCBs. So, this kit needs none of the confusing soldering. You snap in the TFT Raduino onto the main board, plug the power and antenna from the back, snap on headphones, plug in the mic (supplied with the kit) and off you go!

It is offered in two kits now : The basic kit (150 USD) is without the box (like old times) but with a microphone and two acrylic templates for the front and back panels.

The Full kit (199 USD) has the box with speaker, mounting hardware etc. Both are described on the website.

Now, about the TFT display:

For those who are using the 16×2 display and you would like to upgrade, you will have to do three things:

Add a heatsink to the 7805 of the raduino

Buy [here] and hook it up as per [this article].

Grab the new Arduino sketch from https://github.com/afarhan/ubitxv6


I have been hacking away at adding a TFT display for the Arduino for sometime. Finally, I managed to do this with a really inexpensive 2.8 inch TFT display that uses a controller called the ILI9341. The display update is slow but, clever guy that I am, the display very usable. it uses the same pins that earlier connected to the 16×2 LCD display. This display is available everywhere for a few dollars.

Many thanks, Pete, for sharing this announcement. The price was simply too attractive to me, so I just purchased the full kit for $199 US. (Thanks for being the good enabler you are, Pete!)

I’ll post an update when I receive the transceiver and assemble it. I do hope this is a workable little radio–it would be pretty amazing for newcomers to the hobby to be able to get on the HF bands for a mere $200 US. I also love the fact that this is all based on open-source, hackable technologies.

QRPGuys new DSB Digital Transceiver kit

Many thanks to QRPer, Pete (WB9FLW), who writes:

QRPGuys has just introduced a new Multiband DSB Digital Transceiver for FT8.

At $40 it introduces a new price point for such Rigs as it includes band modules for 40/30/20 Meters! For those wanting to experiment with different Bands extra bare boards are available for sale.

The rig as it comes is crystal controlled for FT8 but fear not the main board includes connections for an external VFO. As an example one could use one of the very popular Si5351 VFO Kits and be able to QSY to operate the different modes available to the Amateur Community today.

Let the fun begin 🙂


Thanks so much for the tip, Pete! What a great little project!

Click here to check out the DSB Digital Transceiver at QRPguys.

The Hermes-Lite SDR: an open source QRP transceiver based on a broadband modem chip

Note: This is a cross-post from the SWLing Post.

Many thanks to Pete (WB9FLW), who shares the following:

Don’t know if you are familiar with this project, a full blown 5 watt HF SDR Transceiver for less than $300!

No sound cards, DUC/DDC architecture.

Here’s the project description by Steve Haynal via YouTube:

The Hermes-Lite is a low-cost direct down/up conversion software defined amateur radio HF transceiver based on a broadband modem chip and the Hermes SDR project. It is entirely open source and open hardware, including the tools used for design and fabrication files. Over 100 Hermes-Lite 2.0 units have been successfully built.

The FOSSi Foundation is proud to announce Latch-Up, a conference dedicated to free and open source silicon to be held over the weekend of May 4th and 5th in Portland, Oregon, USA. Latch-Up: a weekend of presentations and networking for the open source digital design community, much like its European sister conference ORConf. Produced by NDV.

Click here to view this presentation on YouTube.

Fascinating! Thank you for sharing, Pete!

FT8 transceiver kit: CR Kits taking orders

The CR Kits DSB Transceiver prototype (Source: CR Kits)

Many thanks to Pete (WB9FLW) who writes:

Adam of CR Kits is now taking orders for his FT8 Transceiver Kit and the price is very reasonable.

From Adam at CR Kits:

FT8 transceiver kit

I start to take email order now. The introductory price is 39 USD for kit including shipping to worldwide. As in the introductory period, you will get audio cable options for free. The earliest possible shipment date is now improved to May 13.

You can directly PayPal to rongxh@gmail.com and let me know 40m or 20m (80m not ready yet). I will ship based on the sequence of receiving your payment. I may delay shipment for one week or two due to workload.

This is the spec so far:

Summary: Crystal controlled single frequency DSB transceiver for 20m (14.074MHz), 40m (7.074MHz) or 80m (3.573MHz), other frequencies could be added per requestPower supply: 10-14V DC regulated power supply or battery pack, 12V is recommended, center positive, reverse polarity protection availableCurrent consumption in RX: about 15mA at 12VCurrent consumption in TX: about 300mA at 12VRF output: about 1W for 40m band at 12V, and a bit less for 20m bandSpurious suppression: no worse than -50dBcAntenna connector: BNC connector, 50 ohmAudio in connector: 3.5mm mono, at least 600mV to activate VOX, connects to headphone connector at PC sound card, no dedicated PTT connector is requiredAudio out connector: 3.5mm mono, connects to microphone connector at PC sound cardAmber LED: TX statusGreen LED: RX statusFrequency accuracy: -600 Hz ~ + 200 HzFrequency stability: Okay for FT8 mode per test. If the optional heater resistor R20* is added, after warm up, long term frequency stability in 10 min will be improved at the cost of acceptable short term frequency stability sacrifice in 30 sec.
Thanks, Adam

Click here to check out the FT8 DSB Transceiver via CR Kits.

How To Convert QRP Labs QCX Transceiver to SSB

Many thanks to Pete (WB9FLW) who shares the following:

This is truly amazing, Guino PE1NNZ has converted the QRP Labs $49 CW Transceiver to SSB.

Not much to add, a ATMEGA328P plus some firmware and a few component value changes and you’ve got a $50 SSB Transceiver!

(Source: GitHub)

This is a simple and experimental modification that transforms a QCX into a (Class-E driven) SSB transceiver. It can be used to make QRP SSB contacts, or (in combination with a PC) used for the digital modes such as FT8. It can be fully-continuous tuned through bands 160m-10m in the LSB/USB-modes with a 2400Hz bandwidth has up to 5W PEP SSB output and features a software-based full Break-In VOX for fast RX/TX switching in voice and digital operations.

The SSB transmit-stage is implemented completely in a digital and software-based manner: at the heart the ATMEGA328P is sampling the input-audio and reconstructing a SSB-signal by controlling the SI5351 PLL phase (through tiny frequency changes over 800kbit/s I2C) and controlling the PA Power (through PWM on the key-shaping circuit). In this way a highly power-efficient class-E driven SSB-signal can be realized; a PWM driven class-E design keeps the SSB transceiver simple, tiny, cool, power-efficient and low-cost (ie. no need for power-inefficient and complex linear amplifier with bulky heat-sink as often is seen in SSB transceivers).

An Open Source Arduino sketch is used as the basis for the firmware, the hardware modification bypasses the QCX CW filter and adds a microphone input in-place of the DVM-circuit; the mod is easy to apply and consist of four wire and four component changes and after applying the transceiver remains compatible with the original QCX (CW) firmware.

This experiment is created to try out what can be done with minimal hardware; a simple ATMEGA processor, a QCX and a software-based SSB processing approach. It would be nice to add more features to the sketch, and try out if the QCX design can be further simplified e.g. by implementing parts of the receiver stage in software. Feel free to experiment with this sketch, let me know your thoughts or contribute here: https://github.com/threeme3/QCX-SSB There is a forum discussion on the topic here: QRPLabs Forum

Click here for full project details via GitHub.

73, Guido pe1nnz@amsat.org

Wow! What a brilliant modification, Pete! Thank you for sharing.