Exploding power amplifier transistors! Hmm…that’s not a good start to any ham’s operating session. But it happened to Hans Summers G0UPL as he was doing development work on the firmware (version 1.03) designed to accompany his very popular QCX transceiver sold through his company, QRP-Labs. Hans, the recipient of the 2019 Homebrew Heroes Award, was doing some firmware enhancements for CAT control of the QCX (version 1.03) to drive an external amplifier when the amplifier’s power transistor …. well, see for yourself.
But what on earth caused the explosion? Here’s where a product donated to our Hero for 2019 came to the rescue. Siglent Technologies donated their SDS1202X-E oscilloscope to Hans as part of their sponsorship. He documents how he used the Siglent oscilloscope to diagnose the power spikes that led to the complete component failure in certain circumstances on his blog.
I had switched the QCX off and on again with the toggle switch on the my front panel, rather fast. There was a bright flash and a loud bang. My QCX is connected to a 0-30V 0-20A linear-regulated bench power supply, capable of supplying a lot of power. Investigation revealed that one of the IRF510 power transistors had blown up quite spectacularly. This photo shows the result. Note that the explosion did not blow the IRF510 pins off; my safe removal strategy for replacing components, is to CUT the component out then remove the pins one-by-one from the board by de-soldering them.Hans G0UPL
Hans explains his diagnostics further, “Investigation with my nice new Siglent SDS 1203X-E oscilloscope (thanks to kind donation by Siglent, sponsors of the Homebrew Heroes award 2019), revealed the following different power-up characteristic, depending on whether the QCX is switched on by turning on the power supply, which is what I normally do, or by switching it on at the toggle switch.
The Siglent SDS 1203X-E oscilloscope has storage features where the display can be frozen by pressing the Run/Stop button at top right. So it is possible to capture an event in “human scale time” with the horizontal timebase running at something like 100ms/div or 200ms/div; then with the display frozen you can scroll it left/right using the horizontal position control, then zoom in on the feature to be investigated, using the Horizontal Zoom knob. Once the display shows the section of waveform of interest, you can use the cursors to make precise measurements of time difference, voltage difference etc. This is very useful to examine and understand features which happen too fast to be seen or captured normally. Screenshots can be captured easily by plugging in a USB flash drive and pressing the “Print” button.”
Hans gives more technical details behind his diagnosis on his blog post but the “nasty” spikes were detected through bench testing and then diagnosing the issues producing it using his new Siglent SDS 1203X-E oscilloscope. This provides a cogent illustration of how our Hero for 2019 goes about his development and testing work for his product line. Like a fine wine, it takes time to ensure that the finished product, whether it’s hardware or a firmware update like in this instance, is working as the higher level block diagrams are intended for it to.
Hans states, “My theory is, that the first PTT signal, at power-up, when coincident with all those nasty spikes at switch on (via the toggle switch), and with the PA circuit not yet settled down (all its capacitors charged up, solid state Rx/Tx switching in stable state, etc), creates the right conditions for catastrophic positive feedback in the PA to set up a huge spurious oscillation which is sufficient to self-destruct, via the explosion of one of the transistors. This does NOT occur in my normal power-up sequence via the on/off button of the power supply. Neither does it occur if I switch off with the toggle switch, wait a second, then switch on again. It only occurred when I switched on and off quickly.” The hand diagram above illustrates his theory of the self-destructing PA transistor.
This does NOT occur in my normal power-up sequence via the on/off button of the power supply. Neither does it occur if I switch off with the toggle switch, wait a second, then switch on again. It only occurred when I switched on and off quickly.Hans G0UPL
The solution? He says it’s an easy fix. “This situation can be resolved very simply by adding a 10K resistor (value entirely uncritical) between the RX signal and +5V. When the processor pins are floating while the processor is starting up, the RX signal is therefore pulled to +5V, until the processor has started and is ready to take over the job. In this fragment of the schematic (below) the additional resistor is shown in the yellow box. I simply soldered it between IC3 pins 13 and 14 which is convenient and easy.” The diagram below illustrates the remedy shown in yellow.
Hans told me by e-mail that, “The QCX + 50W PA is now back in order and I had 9 nice QSOs this morning, with YL Elvira ZA1EM, then E74LZ, UR5MUY, IK7XJA, LZ1HDA, OM3CAZ, R7BW, EW8CP and RW3KE.” So a 10K resistor plus the workbench savvy with a new modern oscilloscope came to the rescue.
The 50W Power Amplifier is a new product that QRP Labs has in very late development. No, it’s actually almost ready to announce with this final change. Hans wrote me today, “Yes, This 50W PA is a new product…This 50W amp is designed as a low cost single-band amplifier for the QCX (which is my flagship 5W CW transceiver http://qrp-labs.com/qcx ).”
The description of the new 50W amplifier was sent to me earlier today and should approximate what will be on the QRP Labs website (always subject to last minute changes, of course). Hans says he is finalizing the manual now and expects an official announcement in a week or so from today. So watch his website for the official announcement. The description is in Hans’ words to me by e-mail earlier today.
This 50W Amplifier includes the Low Pass Filter. It can be built for any of 40, 30 or 20m using the supplied components in the kit and therefore covers 95% of QCX owners. Any other bands would be possible too if suitable inductors and capacitors were substituted in the Low Pass Filter.
The amp kit also includes two substantial heatsinks, which are the same design of custom-made heatsink I use in my 10W Linear kit http://qrp-labs.com/linear. Each heatsink is black anodized aluminium and sized 130 x 28mm, with 25mm fins. ALL the connectors are also included in the kit.
A key feature of the amplifier kit is that it has solid state PIN diode Transmit/Receive switching, which is fast, reliable, low cost and silky smooth quiet… it enables full break-in operation (QSK) which is very important for many CW operators (hearing the band during the tiny gaps between your own dits and dahs). Perfecting the transmit/receive switching took 80% of the development time of the kit.
I have used the prototype for over 500 QSOs over the summer on 40m, working from US to New Zealand, Japan, Northern Europe to Middle East. With band conditions in the doldrums they are, or if people wish to have a sked with a friend at a particular time and location, that little extra power can be very useful! QRP has its place, QRO does too.
The custom-manufactured enclosure kit is extruded black anodized aluminium, size 130 x 63 x 25mm and the heatsinks bolt on the top. On the rear are BNC in and out connectors, DC power connector, and a jack for the PTT signal from the QCX. It is designed to match the QCX but could easily be used for other QRP CW rigs too; it may even work well in Linear operation (with the bias adjusted correctly) but this remains to be seen and tested.
This is the type of bench work that great designers go through, largely unbeknownst to amateur radio operators who purchase their products. Of course, there are issues that get by even the most careful workbench. But here’s a case of precisely why the corporate donors to the Homebrew Heroes Award program have chosen to participate: to give our recipient tools to help that person to do their best work on what they do in the homebrew maker space. To see more of Hans’ illustration of this episode in homebrew development, see his website for a forthcoming video.
Here’s to you, Siglent! And, to Jason Chonko who believed in the HHA program immediately and signed his company on as a sponsor. To see this 200 mhz oscilloscope in action, go to this link.
If you’d like your company’s equipment on the workbench of our next Homebrew Heroe, contact us through the HHA website. We are accepting sponsors for the 2020 HHA now and will announce a new one soon.
The opportunity for the St. Louis & Suburban Radio Club Winterfest event to work with the W9DVY Radio Symposium is a fantastic chance for us to help promote vintage radio and the history of the Amateur Radio hobby. We are looking forward to this relationship between the two groups to bring Amateur Radio operators together. We hope to have a strong attendance and we are looking forward to hosting the great Symposium forums. Rebecca Carroll, KC9CIJ – Winterfest 2020 ChairThe Winterfest is located in The Gateway Center, in the shadow of the St. Louis Arch on January 24-25, 2020. No winter weather worries inside the Center! Lots of hotels at various price points nearby. And there are many other activities, such as Contest College with 10+ hours of forums, presentations, Q&A and contesting discussion, as well as the DX & ARRL Banquet and…the ARRL Midwest Conference with CEO Howard Michel and other staffers from Newington. Ward Silver NØAX is the Banquet speaker along with Craig Thompson K9CT on the Pitcairn VP6R DXpedition. Flex Radio Systems will be there as a vendor with their newest SDR technology, among other popular vendors. See the Winterfest website for more details. There is a lot going on, competing with most any regional ham fest in the U.S. So there’s an additional day-long set of forums at a hamfest. What’s big about that? OK, fair question. Do you use phone when you transmit? If so, you likely use Single Side Band (SSB) most of the time, especially on HF. The Symposium is named for Wes Schum W9DYV (in Chicago, as Bob Heil says he always signed). Wes W9DYV was instrumental in getting SSB adopted in the amateur radio community. Some say he’s the Father of Single Sideband (see Ham Nation, Episode 86). Now that’s a big deal, no? A little bit of history, provided by Nick Tusa K5EF. “The Symposium was formed to honor one of amateur radio’s key advocates of the then-new technology, Single Sideband, and his company’s ground-breaking ideas that culminated in the Central Electronics 100V Transmitter. Wes Schum (W9DYV) introduced single sideband to amateur radio in a very big way, beginning in 1951 with is Model 10A sideband exciter and continuing though his company’s eventual ownership by Zenith Radio, Inc.”
- A High Performance SDR Receiver for the Ham-Bob Nichols W9RAN
- HF Receiver Performance-Rob Sherwood NC0B
- Understanding of Human Speech Articulation-Dr. Bob Heil K9EID
- The Collins S-2 Line History and Evolution-Dave Beckler N0SAP
- Wes Schum (W9DYV) and Central Electronics-Nick Tusa K5EF
- Drake T4XC: Low Power Output and Why-David Assaf W5XU
- ARRL, AM and the story of the Gates BC-1T-Bob Allison WB1GCM
- Another “major homebrewer” presentation is pending
Planning a successful, and growing, hamfest takes vision and the willingness to engage “over the transom” opportunities. You might be surprised at the reticence of some well-known hamfest Chairs and Committees to see beyond last year’s program. Frank Howell K4FMHPlanning a successful, and growing, hamfest takes vision and the willingness to engage “over the transom” opportunities. You might be surprised at the reticence of some well-known hamfest Chairs to see beyond last year’s program. Online sales are eroding the ROI that major manufacturers, their resellers, and the small ham radio business companies get by committing thousands of dollars just to get to a hamfest. Individual sales through boneyards can yield surprise inexpensive purchases but, on the average, hamfests face a similar battle with eBay sales, too. It is programs—the continuing education of hams who spend money to attend a hamfest—that bring’em in, repeatedly over the years. And the Winterfest 2020 team is doing that in spades.
How often have you seen into the thinking process of the development engineering team for an amateur radio manufacturer? Or an industrial test and measurements manufacturer of devices used frequently by amateur operators? In the latter case, the HP Journal was (and still is for vintage equipment) a key source for their line of equipment and often had an in-depth article from the engineers who designed one of their popular test devices. Less so but often with the Tek Journal, too. I always see if there’s a “design article” for any HP or Tek vintage equipment before I make a purchase. While MFJ Enterprises frequently gives factory tours, even for a single visitor, Martin Jue rarely gives public disclosures of the thought process of a device. At least, not until it’s well into production and sales.
But Hans Summers G0UPL, recent winner of the Homebrew Heroes Award for 2019, has done just that! In the October issue of QRP Quarterly (Vol 60, Number 4: 24-38), Hans weaves his thinking and design choices for the SSB QSX multiband, multimode 10-watt QRP transceiver. He’s been publicly discussing the concept since 2017 but rarely do we get this level of detail and insight for a major transceiver release. Oh wait. It’s not a product of one of the major manufacturers so what makes it a major product?
Review the QRP-Labs website on the QSX for the interim specifications and feature set. And pay attention to the projected price. Now, let’s revisit the reticence at calling it a major product release. Block diagrams, schematics, mock-up designs, and the pricing-performance choices going into Hans’ decision matrix for each element of the forthcoming rig are there. Even the case and the choice of no hardware volume control! And the choice of a soft switch for power on and off. The inclusion of several test equipment circuits built directly into the transceiver package ramps up what other manufacturers have included. And did I mention that the target price is $150 USD?
Ashar Farhan made a real splash in the QRP homebrew space when he released the Bitx40 ($59USD) and uBitx ($130USD). There is a small army of builders, modders, and third-party add-ons and case makers surrounding Farhan’s products. But reading the target specifications for “just a little bit more” at $150USD on the QSX QRP transceiver (including a nice case), it will set a new bar for the value proposition in the QRP market place!
And who knew how much the inclusion of a “simple” potentiometer for power on/off and volume control could impact the overall design and cost for a multiband transceiver? If you read this article, you’ll be somewhat shocked and amazed at how the designer’s careful analysis of his product target goals factored into the decision to just not include one. But that’s only one of the interesting twists and turns in this intriguing article on the design of the QSX transceiver.
Read the article and see if you agree with my assessment. QRP Quarterly is edited by Mike Malone KD5KXF. It is the publication of the QRP Amateur Radio Club International with an annual subscription price at $25 USD for domestic subscribers and $28 USD for international subscribers. The QRP-ARCI sponsors the Four Days in May Symposium held in conjunction with Hamvention in Xenia, OH. Hans G0UPL is also a member of the QRP Hall of Fame.
The market shall see what the final version, performance, and exact price will be. Reviewers will leave no stone unturned in putting the QSX through it’s paces when it’s available for retail purchase. But very rarely will buyers know as much about a transceiver’s design and why it was so as with the QSX. The snarky reviews that we almost always see of why didn’t “they” do this or that in a rig will almost all have been answered well in advance of the official release of the QSX. While “they” usually represent an engineering design team, QRP-Labs is staffed by one, Hans G0UPL, Hero 2019.
RIDGELAND, MS. September 4, 2019. “The hits just keep on coming,” announced Colin Butler M6BOY of the Homebrew Heroes Award Program Steering Committee. “We are delighted to include Heil Sound as our newest corporate prize donor to our pending 2019 Hero recipient.”
Bob Heil K9EID said, “Heil Sound is very honored to be a part of the Homebrew Heroes Award. Designing and building Amateur Radio projects has been the basis of my career and I am always promoting ‘home brewing’ so let’s warm up those soldering irons and build something! Thank you guys for making this happen.” The CEO of Heil Sound, now celebrating it’s 50th year, is an avid builder and recent winner of the January 2018 QST Cover Award for his famous Pine Board Project. He launched the Ham Nation podcast on May 24, 2011, some 411 episodes ago. The video podcast is published weekly and includes Gordon West WB6NOA and other well known co-hosts. Bob K9EID continues to elmer a wide audience of amateur radio operators through his popular hamfest forum talks and other demonstrations. He also frequently gives presentations to amateur clubs via Skype.
Martin Butler M1MRB of the Steering Committee added, “I met Bob Heil this year at Hamvention in Xenia. A busy man, he kindly took the time to show this bloke from across the pond his new Parametric Receive Audio System. After 30 minutes or so, I left feeling as if I’d known Bob for a lifetime. He really, really knows the design and building of amateur radio devices!” Committee member Frank Howell K4FMH concurred, “Bob was kind enough to have me on as a guest on Ham Nation on the TWiT.tv network, to discuss the Homebrew Heroes Award concept and what we were trying to build. He followed up quickly with telling me of his desire to have Heil Sound as part of the sponsoring donors. That’s Bob. He’s going to help if he believes in something.”
Heil Sound will provide these items to the winner: Heil Wire, XT-1 Matching Transformer, Heil Stealth connectors, Heil XLR broadcast connectors, Heil 5.1 dynamic microphone element, and
Pro 3 Headphones. All will no doubt be used in the recipient’s subsequent build projects.
RIDGELAND, MS September 2, 2019. A very popular podcast about the ham radio workbench scene has joined the donor list for the Homebrew Heroes Award Program. George Zafiropoulos KJ6VU, co-host of the Ham Radio Workbench show, said, “While we were aware of the Homebrew Heroes Awards Program being organized shortly after Hamvention this year, we were not sure how we could help, other than to promote it on our own podcast. But when Digilent Inc. led the corporate donor list by committing to donate their very popular Analogue Discovery 2 test gear to the recipient, it became very clear. Our new Benchduino kit, which connects directly to the AD2 for design development, is a perfect addition for the 2019 recipient!”
Martin Butler M1MRB, HHA Steering Committee Member, said, “I’ve used the Digilent device, the AD2, and this donation by these innovative chaps just hits the spot for the prize package. The many test and measurement tools in the AD2 when it’s connected to the Benchduino platform just help the homebrewer get things done properly and in short order.” Frank Howell K4FMH, also of the Steering Committee, said, “This addition to our prize donor roster is most appreciated. It exemplifies the spirit of the Award that we are offering: helping others by example, including the fruits of one’s labor at his or her own workbench.” Colin Butler, M6BOY, the third member of the HHA Steering Committee emphasized, “The lads on the Hamradio Workbench show are demonstrating what this Award is about. There addition just underscores the reception of it by the homebrew space in amateur radio.”
Jeremy Kolonay KF7IJZ, co-host of HRW, added, “This just works out perfectly. Our show focuses on what the Homebrew Heroes concept is about: helping the homebrewer and maker audience in amateur radio learn more about the science and craft of designing and building new things.” The podcast has committed to donate multiple Benchduino sets so as to cover the various development platforms the Homebrew Heroes Award 2019 recipient might use.
Our new Benchduino kit, which connects directly to the AD2 for design development, is a perfect addition for the 2019 recipient!George KJ6VU, co-host of the Hamradio Workbench Podcast
The Benchduino is a new project developed and offered for sale by the two co-hosts of the Ham Radio Workbench podcast. An active community of homebrewers have joined the support group at Google.io. The technical specifications are as follows, taken from the HRB website:
The BenchDuino is a development platform for building projects based on the Arduino, Raspberry Pi and PIC microcontrollers. The platform defines a common foot print for processor and expansion boards to make it easy to expand the functionality of the system. The BenchDuino motherboard includes many commonly used peripherals which can be connected to the CPU pins with jumper wires or plug in shunts. The BenchDuino is an open platform and we encourage the development of plug-in CPU and expansion boards.
CPU Boards Available: Arduino Mega, using a RobotDyn Embedded 2560 high end 8 bit MCU; Raspberry Pi Zero; PIC – 40 pin 18F series processor such as the 18F4620; and Adafruit Feather common foot print.
Built-in Peripherals include: (Jumper selectable 5v or 3.3v operation), 4 push button switches, 3 slide switches, 4 LEDs, 2×16 Character I2C or parallel LCD display, 1.3″ I2C OLED bitmap display, 1 Potentiometer, 1 Rotary encoder, Xbee data radio socket, Digilent Analog Discovery II test equipment jack, and various jumper blocks.
The Homebrew Hero Award details can be read at it’s website, homebrewheroes.org. Questions or interesting in joining the corporate prize donor list can be submitted through the website. The promotional partner for the HHA is the ICQPodcast. Martin M1MRB, Colin M6BOY and Frank K4FMH are Presenters on the podcast, now in it’s 12th year with over 300 episodes. The podcast home is at ICQPodcast.com.
RIDGELAND, MS – August 23, 2019 – The list of corporate prize donors is growing for the Homebrew Heroes Awards program. MFJ Enterprises of Starkville MS has agreed to donate a key prize for the workbench of the Hero in 2019. “We owe our corporate success to the practice of homebrew electronics in amateur radio,” said MFJ Founder and President Martin F. Jue. “MFJ is delighted to support this annual award. We sell a high volume of parts to the homebrew and maker community. It’s in our business interests to encourage and support hams and other enthusiasts to design and build things that contribute to this space in the hobby. And, it’s just good business to encourage it, too!” Martin added.
MFJ has identified the popular HF/VHF Two-Port Graphic Antenna Analyzer sold as product number MFJ-225. The 225 uses free downloadable software to access the vector analyzer through a PC. Richard Stubbs, Customer Services Manager at MFJ says that “It has all the basic analyzer functions plus a host of advanced features like a built-in LCD graphics screen, two-port VNA measurement, PC-Interface using IG-miniVNA freeware, precise DDS frequency control, and is self-calibrating.” Mike Enis, Manager at MFJ, says that the MFJ-225 should enhance most every workbench that uses RF circuits, especially through the S-parameters that the device measures, all without a lot of computations required without a two-port vector device.
We owe our corporate success to the practice of homebrew electronics in amateur radio.MFJ Founder and President Martin F. Jue
Homebrew Heroes Award Steering Committee member, Frank Howell K4FMH said that “MFJ’s joining our corporate donor list with this test gear shows leadership in the amateur radio maker space. We are delighted that this corporate list is growing in support of our annual award winner.” Details on the new awards program can be found at its website.
MFJ Enterprises, Inc., was founded in 1972 by Martin F. Jue. The company began operations in a small rented hotel room in the old Stark Hotel in downtown Starkville, Mississippi. The company began marketing its products in October of 1972. The first product was a high selectivity filter that would enable a receiver to separate one Morse code signal from scores of other signals that were being transmitted over the radio airwaves and was offered as a kit to homebrew builders in amateur radio.