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(For some reason Jack has a problem accessing this group) ======================== All: Al and I have just updated the 3rd edition T41 book. We moved the calibration info from Appendix C to its own chapter (20). The expanded instructions and new software make T41 calibration much easier. We have also updated the narrative in numerous places and have concentrated discussions on the V12.6 release where those changes are important. Some of you are asking yourself: Do I need to buy this update. Truthfully, if you already own the 3rd edition, we would say no. Most of the important changes are discussed on the web site and photos and schematics are available there, too. On the other hand, this is the last change we will be making to this book. Al and I have been at this for almost 7 years now and we're getting a little burned out. For that reason, we are turning this site over to Oliver King, KI3P, and Dr. Bill Schmidt, K9HZ. Al and I will continue to be active relative to the T41, but will leave the details to Oliver and Bill. If you do want the final version of the book, its new cover looks like this: The book is actually available now, but the Amazon ad will not reflect the new cover for about 10 more days. (If you order now, it will be the new version.) If you are attending the FDIM conference this May (coincides with Dayton Hamvention and the conference hotel is about 10 miles away), Al and I will be selling autographed copies on Thursday night (May 15th) at the conference hotel starting around 8PM. We have reduced the price of the autographed copies from $12,500 to $40...which is a deal and less than the Amazon price! If you have a previous copy of the book, bring it along and we will be happy to sign it. This has been a fun project and we want to thanks the hundreds of people have contributed to its improvement over time. We hope that continues long after Al and I are gone. 72, Jack Purdum, W8TEE Al Peter, AC8GY

On 4/04/25 I had a CW practice / rag chew session on 20 meters. I worked two stations and had long chats with them: Date / Time Call Bnd Frequency Mode Power Rec Snt Name SPC# Comments Off 4/4/2025 14:12 K0DCR 20 14.04 CW 100 578 569 Dennis CO K3 at 100 watts 100 ft sloper doublet 14:33 4/4/2025 13:12 WB5UTM 20 14.04 CW 100 599 579 Scot LA K3 at 100 watts 100 ft sloper doublet 14:01 Conditions were OK. SSN = 124, SFI = 178, A = 26, K = 4. My next CW practice session will be April 07 at 09:00 EDT / 13:00 UTC on 20 meters. Anyone and everyone is welcome. This practice is intended for operators who are new to CW or they need some practice. IT DOES NOT MATTER HOW POOR YOUR CW IS. Mistakes are OK. Poor fists are OK. Slow speed is OK. Really slow speed is OK. This practice is meant for you to improve your CW. I will do my best to adjust to your skill level. Operate at any power level. If several stations show up, I will operate as a round-table control station. I will do it as a round-table so everyone gets a chance to transmit. Please listen to my directions. Details: Date - April 07 2025 Time - 09:00 EDT 13:00 UTC Band - 20 Meters How to find me - I will find a clear frequency and call CQ. Go to the Reverse Beacon Network and search for my call sign AB8DF. That will tell you what frequency I am on. Tune your station to that frequency and if you hear me give me a call. If there is a QSO in progress, please wait for a break in the action. Then send your callsign. If I hear you, I will invite you to join the QSO and start a round-table QSO. Reply to this email if you have questions. IT DOES NOT MATTER HOW POOR CW IS Ed AB8DF_._,_._,_

Hi everyone, I built the QMX kit configured for 12V operation (the kit was ordered on 13/04/2024), and while everything appears to be functioning correctly, I'm only seeing about 2W of output power across all bands. Here are some data points and measurements I’ve taken: Input voltage to QMX: 11.2V (measured with a Fluke DMM), very stable with minimal drop during TX. Antenna/dummy load: SWR monitor seems to be functional and correspond to nanoVNA measurments. Power display: Only 1 bar (4–5 dots) shows on the PWR display while connected to QRPLabs' 20W dummy load. Measured voltage: The DMM reads ~11V across the dummy load during TX. QMX Console app: Shows 9.5V and between 1.8W to 2W output during TX across all bands. I’m not sure where to start troubleshooting this issue. What would be the best way to begin isolating the cause? For context, I have the following test equipment available: oscilloscope, multimeter, bench power supply and another working QRP radio for reference/testing. Please let me know if there’s any other information I can provide to help identify the problem. I’d be very grateful for any suggestions or guidance you can offer. Thanks in advance for your help! Best regards, Igor — W6ETA 73

My QMX+ seems to be working fine but I just did an SWR sweep and something looks bogus. The SWR is approximately correct for the chosen band but it is flat across all of the frequencies with only a little bit of wiggle. I know my 6BTV SWR is all over the map as you move out of the band limits but the SWR sweep does not show it. I have never noticed this before but I kinda don't want to go back one firmware level and lose my calibration. So, I was hoping some of you are running the SSB code and can tell me if your SWR sweeps look OK? Thanks, Tony AD0VC

Hi Tonight ZL4MDX and I made our first QMX+ to QMX SSB contact. Myles, ZL4MDX is about 200km away. Started on 80m and moved to 40m where signals were a bit stronger. We both agreed that the QRP Labs equipment is exceptional in its performance. Very well done Hans! Greg ZL4GW

Dear group Took me a long time but finally I have finished a build of a Qmx plus rev 2 (my 3rd kit) and when powering it up nothing happens. so I start debug the power supply with the following tests: initially power with 12v (500ma) and nothing no display no nothing power consumption arround 9ma when the button is pressed, I release the button and back to 0ma. so I have check if the 3v out where in ic101 with the button pressed and nothing there. Than the input and strangely nothing there even with the buton pressed. Next step I apply directly 7v on its input and I get 3v on the out put. Seams working consumption also increases to some hundreds of ma meaning the STM32 can be working. then I was checking q101 and q102 and I get when I press the button arround 5v on q101 out and 11.5 on q102 out with 12v input again. the problem is that on the ic101 I don’t see the 11.5 v. Seams that the line is broken. did some one experienced something like this? what should I do next? 73 Azgael

I'd like to know the firmware and hardware rev from anybody who has trouble with the QMX 3.3 and 5.0v power supplies. Mostly, I'd like to know how often these failures occur with the most recent firmware and hardware. If that gets noted here in the forum, the pressure increases to find a more robust solution. Symptoms might be a bad diode at D108 or D109, a fried processor, fails to work after jiggling the power connector, fails to work after accidentally shorting a power supply with a probe, fails to work after multiple short power button presses. As I previously reported, I have some linear regulators on a one inch square scrap of vector board that plugs into JP105, this seems to work well after some minor mods to the QMX. Specifically, need to lift the drain lead of Q106 and Q107 to disable the old SMPS's, need to add 200k in parallel with R112 and R113 so the firmware thinks it's seeing a bit more than 3.3v and 5v (it hangs if it sees a wee bit less) and short drain to source across Q111 so the 3.3v linear can drive ADC_3V3. I'd prefer that Hans change the firmware such that at power up it first checks if LIN_REG_EN is low, and if so skips all the SMPS start up and voltage checks. Then the only mod to the QMX would be to add a 10k resistor from LIN_REG_EN to ground. I don't encourage others to repeat my efforts at this time unless this is simply something you enjoy doing. Odds of blowing up your QMX are greater with my mods and hacks than they are with the old SMPS's. Success is not guaranteed. Reports of SMPS failures are no longer very frequent with Hans' latest firmware, especially given that there are thousands of QMX's in operation. As Hans has said, there are many different kinds of failures being reported in the forum. The majority are due to bad soldering, especially around attempts to burn the enamel off of the magnet wire. Fortunately, most failures are easy to repair. Unfortunately, an SMPS failure often blows the 100 pin STM32F446 processor. I feel that the primary issue with the old SMPS's is that the voltage gets checked by the processor only once every millisecond or so. That's fine if everything works as it normally does, but something unusual can upset things faster than the processor can react. For example, if the 5v rail is momentarily shorted to ground by a scope probe, the processor might increase current to maintain 5.0v but not react fast enough when the short goes away. Designing an SMPS from scratch (or in firmware) is a difficult exercise in control system theory. https://ludens.cl/Electron/loops/loops.html I just received my Kicad PCB fab for a one inch square board to replace my linear regulator vector board. This design has a couple SOT23-6 SMPS IC's. There's a huge number of different parts from different venders to choose from. Max current varies from 500ma to 2A. They operate at frequencies varying from 0.5 MHz to 2.2 Mhz. Cost can be as little at $0.10. Provision is made to allow the board to be fully shielded using cheap copper foil, held up by L shaped header pins. I am designing for the cheapest SMPS IC's which operate at an internally determined frequency, more expensive part (still under $1) can be driven by an external clock source such as a processor PWM pin to eliminate any birdies. The board can be separately built and fully checked out, including how it behaves with an intermittent or varying Vin, momentarily shorted outputs, momentary low current demand, and changes in temperature. It could be temporarily plugged into header pins at JP105 of the QMX, or permanently soldered in place to those header pins. If plugged in, I would recommend adding a soldered wire connection for ground, since if that flakes out momentarily it could be disastrous for the QMX. If it's successful, perhaps we of the forum can make it available as a kit. Or perhaps Hans would like to add it to his shop for purchase. Jerry, KE7ER I started this thread in response to this post /g/QRPLabs/message/139515 Re: QMX+ shutdown problem On Sat, Feb 22, 2025 at 04:10 AM, Kevin (KQ4DTX) wrote: Je