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Hi all SSB firmware was released into beta on 17-Mar-2025 after 9+ months of development. Many thanks to everyone who bravely helped test it and patiently provided their feedback and observations. There are now quite a few YouTube videos, forum reports and other social media mentions about on-air successes with QMX SSB. Now that it has been at least 6 weeks in beta and I believe most of the issues have been resolved, it's time to promote it to an official version. I have called this version 1_02_000 and published it on the QMX page http://qrp-labs.com/qmx where I have also published the updated operating manual, which grew from 111 pages to 134 pages. The main changes are: SSB (obviously!) including CESSB, TX Equalization, Mic AGC, VOX, Pre-distortion and and and... Addition of up to two more USB Virtual COM serial ports (up to three total). All of the hardware tests such as RF and SWR sweep, and Diagnostics, are now available on the LCD too. New CAT commands for LCD contents, S-meter, AGC-meter, Power meter, SWR meter, SSB source Complete list (relative to 1_00_027 the previous official version): SSB modes added (USB and LCB), with CESSB, TX Equalization, Mic AGC, VOX, Phase pre-distortion and more Rationalization of menus, grouped into CW, Digi and SSB submenus (now Keyer and Decoder are submenus of CW) Added up to two more USB Virtual COM serial ports (configurable) LCD versions of AF, RF, Image, LPF, Test ADC I/Q sweeps (miniature graph on LCD) New function PA mod. test to check operation of amplitude modulator Diagnostics screens are now available on the LCD interface too Now remembers previous menu location on ALL menus regardless of nesting level Add way of forcing factory reset, press Menu (left) button during power-up Change TX color in diagnostics screen from red to blue, to avoid confusion since red things are errors Added CAT LC command to retrieve LCD contents Added CAT commands SA (AGC meter), SM (S meter), PC (Power meter), SW (SWR meter) Added CAT command SS (get/set SSB input source) Bug fix: PTT P did not work properly Bug fix: Incorrect PA voltage display on the Diagnostics screen 73 Hans G0UPL http://qrp-labs.com https://www.buymeacoffee.com/g0upl
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I received my kit for a high-band QMX this Tuesday, and have been working off and on over the course of the week to assemble it. I've gotten to the point where it's fully assembled, and after several close inspections under magnifying glass and microscope, I can't find any significant defects that would lead to the problems I've been seeing, outlined below I'm powering the QMX from a 10V, 250mA current limiting DC power supply. The core issue is that the board (That I have never programmed) is drawing far more current than the assembly document suggests it should at this stage) The different cases I've run: Main board connected to power, no additional boards attached: 0mA drawn Main board connected to power, PS #2 board attached, all others detached: 0mA drawn Main board connected to power, PS #1 board attached, all others detached: Initially current limited to ~8-9V @ 250mA. After an inrush period, stabilizes to 10V @ ~100mA Fully assembled QMX: Current limited to ~6V @ 250mA. LCD screen turns on with solid black squares displayed. Appears as a usb device immediately upon plugging in to a computer, without pressing the potentiometer button. I've been focusing my troubleshooting efforts on the interaction points between the main board and PS #1, and haven't found any obvious shorts. Checking the pin header connection to PS #1 with the board attached, I didn't see any shorts to ground. I also double checked and ensured that there weren't shorts around the power amp transistors, and around X201 where I saw VCC being used. I've attached photos of the back side of the main board, and front side of PS #1 as installed under a magnifying glass below. If any other pictures are required let me know and I can provide. Note that there is some debris near the PA transistors in the second photo. I cleaned that and tried again, and the board still enters the current limited condition. Thanks and 73 de VA3KBY
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Hi, I¡¯ve had my QMX+ for a number of months and had tested the then beta now regular SSB firmware with good results except pretty low output power in SSB. As I had never gotten around to fine tune the LPFs when building it I decided this was the logical next thing. So I fiddled with spreading and compressing turns on the toroids and managed to get all bands to between 4 and 5w output for CW except 160m that was already at 6w. Running 12.0v input and build for 12v Being happy with results I then first tested resetting to factory defaults, and then tested SSB output power. Still max 2-2.5w according to the Bird. I then decided to run the SSB calibration again. Worked fine til perhaps 12m or 10m phase. I then heard some terrible noise from the speaker and saw the QMX crashing with all blocks in the display and turning itself off. I tried powering on again, but won¡¯t start now. Just blank display and current protection on PSU kicks in due to over current. I suspect maybe finals are fried with internal short as result? Jonas 7 maj 2025 kl. 23:12 skrev Stan Dye via groups.io <standye@...>: ? On Wed, May 7, 2025 at 01:38 PM, Wiggle Pig wrote: It¡¯s D503 and D504 These are placeholders for diodes that could be placed across the BS170 outputs, as was commonly done with QDX. Hans included them in the design, but has not encouraged installing the diodes, which he believes are unnecessary for QMX. They may suppress spikes, but they also add additional capacitance to the PA, which may affect it adversely in other ways. There were many posts on this list regarding this topic a year or so ago. Stan KC7XE
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QMX+ lucky streak ended
8
Everything has gone textbook right for my QMX+ (kit built) for a few weeks now, but I knew it couldn't last. I was receiving with the USB connected to a Raspberry Pi 4 running WSJT-x and it seemed to be working fine. Then I looked back and the display was dark. Pushing the startup knob drops the regulated voltage to 11v and current limit of 600+mA, which goes back to zero mA when the push knob is released. No idea what happened, but it's down to the basement "bench" to take a look. Film at 11..... -- Brent DeWitt, AB1LF Milford, MA
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QMX Receiving FT8 but No Change When Antenna Disconnected
5
Hi all, I¡¯ve completed assembly of my 60¨C15m QMX. It powers on and passes the RF and SWR sweep tests. Test ADC I/Q shows sine waves, particularly on 60m. I can hear what sounds like FT8 on 7.074 MHz in DIGI mode, and the tones appear to cycle every 15 seconds as expected. However, I¡¯ve noticed that disconnecting the antenna makes little or no audible difference ¡ª there¡¯s no significant drop in the noise floor or change in the signal. Additional observations: The BNC center pin shows ~0 ¦¸ to ground (I understand this is expected due to the SWR bridge). BNC center has continuity to one side of C510 and C526. Test ADC I/Q and scope work as expected. Reflowed L506, L508, L510, L511, L512, and L513 for better LPF continuity. I¡¯ve confirmed IC402 pin 13 is not grounded, but I don¡¯t have continuity from the BNC center to pin 13. At this point, I¡¯m hearing what I believe is live FT8, but the lack of change when removing the antenna is making me question whether the antenna signal is actually routed through the intended receive path. Would appreciate any guidance or suggestions for what else to check. Thanks! -Tanner
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Hello. I'm assembling a 50 watt power amplifier for use with a QCX+ that I assembled last month, for the 80 metre band. I have very high harmonics at the output of T3 - as a result, I get only about 9.3 watts out when running at 13.8 V. Output from the LPF looks OK on the 'scope. I found the excellent videos by NA5Y which shows the output of T3 should be much closer to a sinusoid than what I get. I also found the discussion with KO1KR in August of 2020, but unfortunately I can't see his scope photos so I don't know if he had the same problem. I've since skimmed through the many discussions on this forum but haven't found the same issue exactly, though I did check out some of the suggestions given here. I found the amplifier took 67 mA with R5 fully CCW - I adjusted R5 till the amplifier drew about 70 mA with the QCX+ key-down in practice mode. Here are my scope traces: 0092 is the gate drive, yellow is Q1 gate, purple is Q2 gate - all is well here. 0090 is the drain voltage, Q1 in yellow and Q2 in purple - these look like there is oscillation ? 0091 is the voltage at the output of T3. This has a lot of third harmonic and doesn't look like the waveform NA5Y showed at this point. (QCX+ was set for 3.520 MHZ , amplifier connected to a dummy load.) I thought that perhaps my bench power supply is doing something odd when the amp is drawing power, but I probed the 12 volt line right at the barrel connector and the 'scope showed almost no disturbance of the +12 v supply. In frustration, I observed the output of T3 with the 'scope set for a long capture - it almost looks as if the distortion grows with time, for the first few tens of microsceconds the scope showed a small but sine-ish waveform, which over the span of a few hundred microseconds got wigglier and wigglier till it developed into the mess seen in my scope capture 0091. I've checked DC continuity to the windings of all the transformers and coils. I did find a bad joint on the primary of T1 but I cleaned it up and can now get power out of the amplifier. I haven't yet checked bias on all the 1N4007 diodes but the input looks quite sinusoidal at R3 closest to the input. The few watts the amplifier does produce look OK at its output. The QCX+ makes about 4.3 wats into a dummy load (43 V peak to peak) at 13.8 V DC. I'm assembling these units for a friend, and I had really hoped to have them ready for Field Day this year. The instructions are excellent and I have followed them closely. What can I look at next? Bill VE4STW
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Blown Q504 - heat dissipation was not ok
2
My QMX+ stopped working after a few FT8 calls. One of the BS170 transistors had blown and there was a short circuit to GND via Q507. While I was replacing the transistors, I realized the possible reason for this: The BS170 housings are not necessarily exactly the same height, one of the transistors was loose under the washer and slipped out. I only noticed this because I hadn't soldered them yet. If I had soldered the transistors first and then put the washer on later and tightened it, I wouldn't have noticed this. And I think that was also the problem that led to my burnt-out Q504 in the first place. The heat dissipation to the circuit board didn't work properly because the transistor wasn't pressed onto the circuit board properly. I took another look at the assembly manual. It does not explain exactly how to install the transistors and in what order. I think a comment on this possible problem would be good. gl tu es 73 de J?rg DJ4WD
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QCX+ adjustement and alignment
4
Checking my newly built 20M band QCX+ I found the following facts: On a 50 Ohm dummy load - with a 13.5V DC supply I only get around 3 Watt output; - 8.7 Peak BPF looks OK; - 8.8 I-Q Bal 8.9 Phase Lo and 8.10 Phase Hi show high minimum values; After connecting my AlexLoop magnetic antenna I get only noise where I should ear some CW and around 14,074 some FT8 noise. I went to 15,000 MHz to ear the hour signal but nothing except a continuous signal on 15,005MHz. Para 7.3 page 130 of the manual writes: "Your results may vary depending on your Low Pass Filter inductor construction! If the cut-off frequency becomes too low, then you start to get attenuation at the operating frequency. In this case you can remove one turn or two from each toroid." As the LPF work both in Rx and TX I understand that if their cut-off frequency is too low I loose Rx sensitivity and TX output power. Do you think I should actually start by removing one turn on L1, L2 and L3? I guess it would just raise a little the cut-off frequency without increasing the 2nd and 3rd harmonics? 73 - Pierre - FK8IH
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QMX + won¡¯t show up as thumbdrive
3
I have been trying several times to update my QMX plus to the newest firmware without success. The computer does not recognize the QMX plus. Just for giggles I updated both my QMX¡¯s Without any issue. I plugged them in like normal and they showed up as the thumb drive. What am I doing wrong? I¡¯ve searched this topic and cannot find anything. Appreciate all the help. -- Trevor (N0YMA)
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RF Amp using the now cheap GaN-FET's
13
Starting a new thread. Scouring the web, here's mention by KG7AGO of using a GaN-FET similar to the INN650D240A getting 300 W on 20 meters with a 60v supply. https://www.qrz.com/db/KJ7AGO https://amfone.net/Amforum/index.php?topic=47457.0 (search for KG7AGO) The amp would be more efficient at a higher supply voltage, but to keep heat down we'd need a higher turns ratio on the output transformer. Not only does the higher voltage reduce resistive losses due to the internal Rds, it drastically reduces internal capacitances. These parts are rated for a Vds_max of 650v A power out from a 100% efficient current mode class D power amp is given by this paper https://repositorio.inesctec.pt/server/api/core/bitstreams/4b52de91-5d27-41cc-acc2-70feeca9a7c7/content His equation for power out resolves to this python script: def pout(Vdd, R): return(3.1416**2 * Vdd**2 / (2 * R)) Also, the peak voltage for a current mode class D amp is pi times the DC supply voltage when properly loaded. I have figured out where that math comes from, would be happy to explain if anyone is curious. Trying that formula out for 50 Volts DC into 50 Ohms (a 1:1 turns ratio) we get: pout(50, 50) # 246.7 Watts We get the same 246.7 Watts with 100v into 200 ohms (a 2:1 turns ratio, peak Vds of 314v) 150v into 450 ohms (a 3:1 turns ratio, peak Vds of 471v) 200v into 800 ohms (a 4:1 turns ratio, peak Vds of 628v) Power out is proportional to the square of the DC supply voltage, for a given turns ratio we can reduce heat by reducing the DC supply voltage: 100v into 800 ohms gives 61.7 Watts, or 1/4 the power at 200v From the datasheet for that $0.04 GaN-FET (on JCLPCB website) https://www.innoscience.com/uploads/61af2c81/INN650D240A_Datasheet_V1.0.pdf it claims to be able to dissipate 75 Watts into a 25C heatsink. As Allison notes, the package is not easy to attach to a heatsink. I think we could have JCLPCB solder it down to a small multilayer board with lots of thick copper planes and lots of vias, then bolting that board to a heatsink. Should dissipate maybe 20 Watts, good enough for a 100W amp. Make those boards available for $5 or less. If the Gan-FET's fail, replace the board. Jerry, KE7ER ######################################################### I hijacked this other thread with talk of GAN FET's for an RF amp /g/QRPLabs/topic/113293149#msg146121 On Sun, May 25, 2025 at 04:44 PM, ajparent1/kb1gmx wrote: I've worked with GAN mosFets and that was 10 years ago. The ones I used easily ran at 15mhz very high speed 20W switcher. The TI driver chip was the real limiter. The GAN devices were froom EPC. And yes they can make very efficient amplifiers. They are optimized for switching and with very low RDSon and fast switching speeds they don't get very warm. Never tried them in a linear class A or B format. Cooling a beamlead chip 120x40x 60 mils would be a mounting challenge for most. One would hope for a flavor of a flange package. On Sun, May 25, 2025 at 03:51 PM, Jerry Gaffke wrote: Anyways, I was hoping you might ask some questions about that $0.04 GanFET in the other thread. Near as I can tell, two of those should make a dandy legal limit amp. Probably fine at 4mhz, but cooling those suckers at 30mhz might be an issue. /g/QRPLabs/message/146094 It all started with this post in yet another thread: /g/QRPLabs/message/146094 On Sun, May 25, 2025 at 09:09 AM, Jerry Gaffke wrote: Moderately high power RF parts for linear amps don't have much of a market, they come and go. The MRF101 and MRF300 seem to be the primary choices these days, who knows how long they will be available. For decades the low end amateur gear has been using the IRF510 to achieve moderately high power, occasionally with a half dozen of them in parallel. But the IRF510 is not designed to be linear and also requires a fair bit of gate drive, making a linear RF amp a difficult challenge. Polar modulation should ease this situation. I've been looking at some of the GanFET's. These can be high powered devices with very low internal capacitances. The
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QMX+ Power Output
11
I just finished my QMX+ and thought I would share my RF power out readings. I did my best to wind all the torroids evenly though not perfect. Measurements are made with an Oak Hills QRP meter into 50 ohms, and with a LiPo supply voltage of 13.4 volts through a single diode. Voltage at the rig when keyed is just below 12 volts. 73, Gary W8PU 160 m - 5.9 w 80 m - 5 w 60 m - 3.9 w 40 m - 3.9 w 30 m - 3.7 w 20 m - 3 w 17 m - 2.3 w 15 m - 4 w 12 m - 2 w 10 m - 3 w 6 m - 2 w
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New Chat: Serial Number Recovery w/o Order Number
#chat-notice
A new chat has been created: Not sure where to ask this, so will try here: My wife purchased a 40m QCX-Mini kit in the fall/winter of 2023 as a Christmas Gift. She ordered as a guest and got rid of emails related to the purchase, so I don't think I have a way to get the order number. Is it possible to lookup the order/serial number based on an email address and/or a delivery address? I have an itch to laser engrave my enclosure with the S/N, band, and options (TCXO and AGC). This is the main reason I'm interested in recovering the S/N. Thanks! Ben (KF0KXW) By: balexander87@... View/Join This Chat Do not reply to this message to post to the chat. You can participate in chats only through the group's website.
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(Silly) soldering question
9
#help
#kit
#QMXplus
#solder
#tip
I've successfully have built many kits, but I always wondered.... I push the thru-the-the board component leads from the top of the board thru to the bottom of the board. I've always wondered, for thru-the-board components, should I solder the component thru lead and pad on the bottom of the board, or should I solder both sides of the component lead (top and bottom of the board)? And if I only solder the component thru lead and pad, should I see solder flow on the top side of the board/lead? Thanks, Roy de K2RMA
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Elecraft T-1 tuner usage
11
Could someone please explain to me a simple, quick, non-fiddly way to send a signal that my T-1 tuner can use to tune itself? I tried searching the forums but didn't find anything. Thanks all.
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QMX Plus PC Board
4
Anybody know what those two shiny blobs between R205 and R208 and Q204 and R210 are for? They show up on page 2 of the schematics as JP202 and JP204. Thanks.
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QMX+ receive current; what's typical?
4
My QMX+, a factory 12v build, draws 160ma at 9.28v, the voltage at which I operate for tx/rx. for all modes. Transmit current is consistent with my readings. The various PDF manuals I have searched, speak of ~80ma for rx. I am interested to know if mine is a typical, and how it compares to other build and operating voltages between 9v and 12v TIA, Pete/wa4hei
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Hi everyone. With the release of the SSB firmware out of beta, I thought I would make my offer to source K6ARKs wonderful little microphones, which can be found here: https://www.printables.com/model/320559-mini-microphone-for-qmx-trusdx-usdx-kx2-and-kx3, one more time. Adam (K6ARK) made a super fantastic little miniature mic case, and they work with the QMX quite nicely. I print the cases in PLA, and have the following colors available: Black, White, Grey, Navy Blue, Orange, Light Green, Red, Gold, Purple, Sand Stone, Light Blue Stone, Turquoise stone, and Marble Stone (The stone colors look like marble or granite - little flecks of darker color in them - The marble one winds up looking like bleached bone). The kit includes: 3D Printed case in PLA 3.5mm jack Electret Mic Element Microswitch for PTT For each mic, $10 for kit, $15 fully assembled and tested. This price includes shipping in the US. I am happy to make you more than one, some people want one for home and one for the go bag, that's great. You will need to provide your own AUX cable (3.5mm male to male) to go between the mic and the radio. I have had several ask what cord I am using, So I have included this link to one I am using and that I test all my assembled mics with; it seems to work quite well: https://a.co/d/36GDDXf (This is a shortened, non-affiliated link to Amazon.com page for the cable I use) If you are interested, send me a private email, and I will send you payment details. My email address is good on QRZ.
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#qmx #troubleshooting
16
#troubleshooting
#qmx
Hello everyone. My name is Jesus. I recently purchased a QMX multi-band multi-mode transceiver with the 80/60/40/30/20 version. I assembled the radio and made sure to perform checks to ensure there was no shorts to ground. I proceeded to power up the radio and the radio did not power up. There was no power consumption. A quick inspection showed the D103 on one of the SMPS boards was sheared off possibly during shipping, maybe on assembly? Regardless I ordered 2 sets just to be safe. I installed the new set of SMPS and attempted to power the QMX on again. The transceiver still does not show signs of life. No power consumption showed on the meter. I did some checks with my limited knowledge. Power seems to be getting to the SMPS. Ground is in tact. There is no 3v or 5v output from the SMPS. The board does not power on or register as a device via my PC. I wanted to reach out for some guidance on any additional checks I can perform? I double checked all the solder joints with a microscope and can¡¯t see any bridging that could short anything out. So I¡¯m suspecting there¡¯s an open somewhere I¡¯m not seeing.
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QCX Challenge
4
13:00 session only Jorma OH8TX remembered the date without announcement. Lets hope others will have time for 19:00 Martin DK3UW
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QMX+ onboard microphone
8
#QMXplus
What's the short story on why the onboard QMX+ microphone doesn't work (yet). Is there an upcoming solution? Just curious, Roy de K2RMA
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