Re: QMX CW issue, omits dits
Thanks for the ideas so far.
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As I am used to Iambic A I also choose this option on the QMX.
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Incoming RF obviously is not the problem as this issue also occurs in practice mode. To be shure I tried a dummy and got the same result.
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Could it be that the processor is not fast enough by handling the paddle input? I found that the QMX occasionally even does not send single dits as for an 'e' letter. In one case after sending some text with medium speed (20) the QMX hang by sending a continuous tone so I had to switch off power.
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None of my QCX showed this behaviour at any time.
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I am puzzled...
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73 de Michael DF9TZ
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Really liking my QMX+ too. There are still a few things I don't know how to do yet, but overall it is just what I wanted for my bedside station that I use before going to sleep. Worked Slovenia from Ohio a couple days ago. Awesome.?
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Re: Help with partially fried QMX
Sorry for OT.
Hello Stan, thanks for your praise. But for me it's dangerous to believe in it. You only don't know when I was wrong :-).
73 Ludwig
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I’ve had my QCX+ up and running for a couple of weeks now at home, and have made many QRP qso’s on it and a OCFD. ?I find the hobby so rewarding using a new language I learned recently, and using a rig that I built! ?Thanks goes out to QRP Labs for great kits! ?Anyone can build these kits with patience and a hot iron…if I can, you can! ?Can’t wait to get outside here in Northern Minnesota with the QMX, Spring is just springing up here.?
Thanks Hans!?
72/73
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Trevor (N0YMA)
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Re: First attempt at WSJT-X failed
Just a quick comment: If You use Icom ATU such as AH-4, the tuner has a buildt-in attenuator that attenuates the RF signal something like 15 dB while?tuning. Hence?showing approx 50 Ohm impedance even while tuning.? The tuner is specified to have a 5-15w input signal, but in my experience it works also from 2-3w.?
A simple interface for starting the tune process with Icom ATUs can be buildt like this:? 
This is likely due to your use of the antenna tuner while transmitting at full power.? When that ATU switches its relays to find a match, it presents momentary 'high SWR' to the QMX, causing it to go into SWR protect.? [Depending on your ATU, this may also happen even if it doesn't 'tune', when it switches to its tune memory settings for the current frequency.]
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What I recommend doing is disabling the 'auto' on your ATU during normal operation, and when you change bands/frequencies and need to tune again, turn back on the 'auto', and use the QMX Hardware tests -> Tune SWR feature to give a reduced-power signal to activate the tuner auto-tune.? The SWR protect is automatically disabled in this mode, and the reduced power will remove risk of blowing your finals due to high SWR.? The default setting is 50% (voltage), 1/4 power.?? If this is too low for your tuner, turn it higher, maybe up to 75% (Protection menu -> Tune %).? This is how the QMX was designed to adjust tuning.
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Some others don't like to do that, so they disable SWR protection, or set its threshold very high, so it won't trip when the ATU switches.? But do this at your own risk: it will likely work fine for a good while - but the momentary high SWR events may eventually wear down your finals and blow them.? There have been a few posts in this forum in the past about blown finals due to ATU switching.
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Or just use an antenna that already has an SWR of about 1.7 or less - and don't use a tuner.? There is almost no functional difference in tuning an SWR of 1.7 down to 1.0 vs. not using a tuner.? The small loss in the tuner inductors is about the same penalty as a bit higher SWR.
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Re: QMX repair and diagnosis by W1NC
Yeah I made a few mistakes on mine. ?So thankful Jeff was able to bail me out.
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Re: Available Hand Mics for QMX SSB ?
Certainly!??
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For anyone who wants to print their own:
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If anyone wants a printed version with the threaded insert already in and the screw, DM me.? I have a few colors other than the one I used for the picture.
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73
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Re: QMX pre-build 97775 has arrived
You're absolutely right Mark; Hans designed marvelous little transceivers. Mine are working great.
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On a cautionary note, you might open the Operations Manual and fast scroll (hold PageDown button), stopping wherever you see RED text. Hans did a fine job of offering warnings in the manual.
Other parts of the manual I found most helpful were about the CW Filters and AGC.
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72 de N4REE, Bob Easton - QRP CW forever
https://bob-easton.com/n4ree
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QMX - Constant 700Hz Tone on 40M, 17M, and 15M Bands
Hey everyone,
I recently bought a ready-assembled QMX after my DIY attempt didn’t quite work out (let’s call it a “successful failure” ?). Funny enough, I had no issues building the QMX+, QDX, or even the QCX Mini before.
With the assembled QMX, I’m getting a continuous tone every 700Hz on the 40M, 17M, and 15M bands. All the other bands are working fine.
Here’s what I’ve tried so far:
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Factory reset
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Upgraded to the latest beta firmware
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Tested with different batteries and power supplies
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Swapped USB cables
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Connected to both a laptop and an iPad running iFTX
One key observation: these unwanted tones only appear when an antenna or dummy load is connected. Without any load, the issue disappears. That makes me lean toward a hardware issue—maybe something in the PA section or related to RF feedback.
I’m attaching some test results in case anyone spots something I may have missed. The timeslots on the JTDX without noise is when I disconnected the dummy load.
Any thoughts, suggestions, or similar experiences would be greatly appreciated!
Thanks in advance!
DL7EDU - LU5VQV
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Martin,
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I've seen these on other bands as well and I'm fairly certain that this is an RF artifact that comes from the USB connection signaling.?
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See if you can lower the amplitude of those spurs by adding a common mode choke to your USB cable. I haven't been able to eliminate them completely but I have been able to drop them to an acceptable amplitude.
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Greg,
N1TR?
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Re: Available Hand Mics for QMX SSB ?
The printed case for the qrp guys microphone looks awesome! Are you considering sharing the design?
I too have an aversion to taking a beautiful circuit board and stuffing into a pvc tube!
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73
Jim K8JK
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2 Audacity files how? 6 m sounds in Digi and CW
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Martin
DK3UW
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Re: QMX CW issue, omits dits
Michael,
Just put a common mode choke 10 feet from your rig in the antenna coax line. ?I have had RFI cause all kinds of strange interference with my experimenting with all my QRP rigs. ?I have found that a CMC at 10 feet has “cured” many strange problems I have had in the past 10 years.?
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On Apr 14, 2025, at 7:59?AM, Michael via groups.io <michael.wohlfarth@...> wrote:
? Meanwhile having some QCX mini, now also own a QMX. Unfortunately I experienced a mysterious issue while keying CW that I don't know from the QCX. Every once in a while the QMX keyer omits a dit or a dah. At first I thought of a contact problem of my morse key (BaMaTech) but on my WinKeyer it worked flawlessly. I tried several speeds but even at low speeds this issue was present. After some futher experimenting with some alternative configurations and with other morse keys I think this is a problem of the QMX. I have firmware 1_00_027.
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Any ideas?
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73 de Michael, DF9TZ
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On the WSJT-X I have birdies or whatever they are, which I don't have in CW mode I do have this continuous tone over the whole band as reported before.
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What can that be?
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Martin
DK3UW
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Re: First attempt at WSJT-X failed
On 14/04/2025 21:40, Stan Dye via groups.io wrote: But I don't think you should.? WSJT-X authors recommend 60 or below, and raising it won't improve your receive performance. Stan, The current thinking is to run the ADC as high as possible without it actually being overloaded. (The bar goes red.) I have the feeling that this is theoretical, I've not seen any research proving more decodes are made. (Not an easy task given the wide variations in band conditions.) I'm fairly certain the difference is at best marginal. 73 Alan G4ZFQ
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Re: Available Hand Mics for QMX SSB ?
I have yet to try the K6ARK microphone that I assembled using this mic as well.? Good to know that if it isn't performing quite well enough that it might just be a swap to get better performance.? Thanks for that tidbit Erik and Stan!
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I also have a QRPGuys mic to try out soon too.? Just finished printing a case for mine as I'm not particularly fond of a PVC fitting.
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73,
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QMX pre-build 97775 has arrived
Hooked up power, speaker, paddles and antenna.
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Powered it up, looked for and found the VOX and turned that on, looked for and found how to change from straight key to paddle, changed speed to 17 wpm, and we’re off to the races.
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4.5 watts out on 40 meters with the 9V Bioenneo (9V build).? ??What a blast.? Worked N2TTL in Florida and was spotted by Germany from one of my CQ’s.
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I have not even opened the PDF for the manual, although I have downloaded it.? So far, everything I have needed? to change has been discovered by scrolling through the menus.
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Hans, you’re a genius.? The user interface is fabulous and intuitive.? I’m no rocket scientist…I am an engineer.? And if I can get the hang of this without opening the manual, then you did it right!
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THANK YOU!!
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Mark Lunday, WD4ELG
Greensboro, NC ?FM06be
wd4elg@...
SKCC #16439 ?FISTS #17972 ?QRP
ARCI #16497
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Per first question, I checked for Q103/Q104 short while building as Hans described in video.
Looks like I have Q104 and Q106 both dead.
Once I picked drains of both off PCB - I can pass at least test 1 and test 2 for PCB#1
For now I cannot test further as tests 3 and 4 require these MOSFETs alive. I'll check if I can source these as a replacement.
I also tried PCB#2 test and at 5.6V it draws ~120 mA immediately and VDD is just ~1.0V - I now wonder if another BSS123 is bad.
I think for now my main concern is the root cause: could main board's short/missing connection fry power board in this way?
If I repair or replace power boards - would I fry them again?
Thank you Stan for continued support.
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Stan,
Thanks for the tip on using the QMX at 1/4 power to set the tuner after a band change. That works and now I don't get the dreaded "S" after the frequency.
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I don't intend to use the QMX in the shack but I wanted to do something to see if it worked before I introduce more variables in the field. Probably use a Wolf River Coil in the field. I also have an EFHW to try.
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I am learning more each day.
Jim W0RLD
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Stan, as requested, here is Jeff Moore's summary of his findings on my rig that was exhibiting wildly fluctuating bias current and simultaneous fluctuating output power.
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Jeff found under microscopic exam, that the Q516 transistor had been damaged either in manufacturing or shipping. He also found and replaced a faulty TCXO.
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I commend Jeff (W1NC) for his amazing skill and generous support of our QRP Labs community.? For the mere price of parts, postage, and a voluntary donation so he can assist other hams, a rig sent to Jeff is returned in the best possible operating condition.
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Here, in Jeff's words, with his permission, are his findings on my radio:
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Here is what I found and did:
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1) Disassembled all boards, scraped off old flux, cleaned with 99% IPA
The reason I do this on every rig is that it forces me to look closely under the microscope at every solder joint and component. ?
Often solder splashes or cold joints can be hidden by the dried up old flux.
2) Inspected under 10x - 20X microscope
Display / Control board
Nice job!
The Main PCB had no issues seen
3) Powered up at 6.1V and installed rev 27 of firmware
Factory reset - all good
The reason I use 6.1 volts is because it’s the lowest voltage that will allow the rig to operate (except for TX) and will minimize damage is something is terribly amiss.
4) Tested on bench at 6.1 V Controls, buttons, encoders, AF, image scan, A/D scan and rf scan functions - all found to be good
5) Shut down rig and increased voltage to 12v.? Tested LPF & TX functions on all bands at 12V.?
Power out fluctuated and bias current all over the place
Diagnosed to a faulty Q516 transistor - You can see a crack in it under the microscope.
Replaced Q516
Now power out is constant and bias current steady at 30ma
LPF shapes and cutoff frequencies all good
TX bias current is correct for every band (30ma)
TX power reduction (to about 1-2 watts) works well for LPF scans - This is an important test
SWR bridge works well for all bands
6) Measured minimum discernible signal on all bands - < .02 microvolts - very good
7) Measured frequency accuracy - not close to setting
Measure TCXO output - found a very odd and varying waveform
Replaced TCXO - This is a tough chip to replace
Now frequency accurate to within 1 Hz
8) Measure spectral purity on all bands - easily exceeds FCC requirements and meets QMX design goals
9) reassembled into case and retested everything one last time - now 100% RX, TX all modes, all bands
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Total time spent - about 3 hours"
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I hope this info sharing helps others who may encounter this bias current misbehavior.
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72 and 73,
Bill? W3WJ
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Braden Glett
UPNORTHOF48 :
Jason
N4REE - Bob
James Kvochick
David Wilcox K8WPE