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Hi all, first off, thanks to Jeff Moore who helped my QMX midband, and noticed my silly mistakes. Second off, I've just finished a QMX plus and am fairly happy with it except for the fact im getting 2-3 watts, leaning closer to 2 on all bands except 160m. I've reflowed all LPFs, PA, and tri toroids. Any ideas on where to look next? I dont think i have any failed finals or shorts.

I finished the QMX7build and have applied power, No Smoke but also not seeing a flash drive, Steps so Far: Limited the supply voltage to 7V Limited Current to 350mA Applied power and did not see any voltage or current as expected. Pressed the Left Encoder and saw a voltage drop AND the mA jump to the 350mA limit Release button and the voltage returns to 7 volts and mA is back to zero. No USB Flash Drive shows up. Tried Pressing the Left encoder again, same results, Voltage drop and mA to 350 limit while the button is pressed. I have searched the group for steps to troubleshoot but since I don't have the firmware loaded I am not sure where to start looking. I have looked very closely for any cold joints or bridges or anything that looks out of place. Is there a guide I can use to help trace / Trouble shoot? Thanks Bill

discovering more things on the rig. I finde, that the min. audio volume is still quite high but could not find a setting to alter that ( apart from muting it) -- Martin DK3UW

I finished my QMX+ kit 2 weeks ago. I built it for 9V, and held my breath as I powered it up for the first time. Everything seems to work fine, and all bands receive and transmit. I called CQ a few times on CW and saw typical results on the reverse beacon network. I have also worked some FT8 on various bands. So overall, I feel like it is a successful build. That being said, I do have a question about the power output. Running into a dummy load, I get the output as listed below. Are these figures typical on the higher bands, and if not is there anything I can do to help increase the output to where it should be? 73, Jim (w8ykg) 160M 5 Watts 80M 5 Watts 60M 5 Watts 40M 4 Watts 30M 4 Watts 20M 3.5 Watts 17M 3 Watts 15M 3 Watts 12M 3 Watts 10M 2 Watts 6M 1 Watt

Hey all! Got my QMX+ rev 3 last week and have had a blast assembling it over the past few days. Finished it last night, booted just fine, and was able to tune some CW on 10m with a big grin on my face ? The thing of it is - after a few minutes, it froze. The LCD contrast went a bit darker, audio output stopped, and all front panel controls had no effect. Unable to power off by holding the VOL encoder, I had to cut power at the source. A short time later I was able to boot back up, browse some bands, tune some CW, and then it freezes again. Same symptoms: LCD goes higher contrast, audio stops, all controls stop, have to cut power. I'm pretty new to debugging PCBs but figured I'd dive in as best I could to gather some info, and here's what I've been able to piece together: I wired it for 12V, and based on measurements my battery was delivering consistent 12.13V Contemporaneous with each instance of the board freezing was a drop from 12.13V down to 12.0V I checked a number of the components around the PWR_ON and PWR_HOLD circuits, and no blown components However, the measured voltage across R105 went from ~3V (normal operation) to ~4V (frozen) No smells or popping sounds like components faulting/failing No changes to the LCD indicating on-board protections or anything like that Tried running 9V in case there were unobserved fluctuations in my power source, but it was the same behavior - a few minutes of normal operation, and then freezing measured voltage during operation was around 7-8V I've tried connecting to the serial terminal to check the on-board diagnostics, and that seems to be the most consistent way to trigger a freeze. Without trying to connect a terminal, I can usually get about 2-5 minutes of normal operation between power cycles, but as soon as I attempt to connect the terminal, it freezes. Like I said, I'm new to a lot of this but eager to learn so forgive me if there's obvious debugging steps I've missed ? ??. But yeah, not quite sure where to go from here! Would greatly appreciate any help or pointers!

I am finding the brightness of the QMX display to be too high. I want to increase R306 (33 ohms) to lower that. I'm thinking about 100 ohms. Any other suggestions as to what would be a good starting point?. -- 73, Dan NM3A

I just noticed a funny thing . My Logging software indicates the QRG and when in A&B it indicates VFO B and not the receiving VFO A. On transmit it then changes to the QRG of VFO A but transmits on VFO B. Is there a bug in the CAT ? -- Martin DK3UW

It occurred to me that the Interface between the ACT08 drivers and the BS170 gates could be AC coupled. A quick simulation with 100nf and a 2k to ground on the gates shows no ill effects. The advantage is two-fold. First, a BS170 failure that puts 12V on the gates is less likely to damage the ACT08 outputs. Second, any failure that leaves the ACT08 outputs high for a long time is less likely to fry the BS170s. Just a thought. Tony AD0VC

SO i had a working qmx rev 2 - purchased assembled - i was swapping my antenna coax from another radio and poof the QMX no longer powers up . I also had a kit so i swapped out the PS boards . Still no luck . i tested the power supply boards individualy and they work fine . After furthur trouble shooting i discovered that the Lin_Reg_EN signal is stuck at .7 volts with 10V in . I tried tacking a pull down resistor ( 10k ) to ground and it lowered it by maybe 20 millivolts . Sounds like i have a bigger problem . Any suggestions

I recently received my assembled QMX+. It is a very neat transceiver, well designed and nicely built. I have played with the USB, reading the IQ samples from the 20-bit, 48-kHz ADC. The QMX+ is in CW mode and IQ is enabled. I cannot find information on the architecture, but I guess it is like follows. The antenna signal passes through the bandpass filters to the Tayloe detector. The frequency to the mixer is the dialed frequency minus the IF frequency of 12000 Hz minus the side tone frequencey of 700 Hz. If I dial 7020 kHz the mixer will use (7020000-12000-700) Hz = 7007300 Hz. The resulting product passes through an amplifier with a lowpass filter in front of the ADC, about 24-kHz bandwidth. The sampled signal has two channels, I and Q, real and imaginary part. These signals, which have a bandwidth of ±24 kHz, are available at the USB port. If I listen to a CW signal tuned to 7020 kHz, it appears as a +12700-Hz signal on the USB port. The CPU in the QMX processes the signal by mixing it with 12 kHz (complex sine, exp(jwt)). The resulting signal, I/real part only, (appears at +700 Hz), is then passed through the CW bandpass filter, nominally adjusted around 700 Hz. I have attached a PDF sketch of my understanding. Is this description correct? I experiment with a configuration where the CW filter is a (IQ/complex, two equal channels) Gaussian low-pass filter around zero frequency with a bandwidth of 10-50 Hz. This corresponds to 20-100 Hz bandwith in a bandpass configuration. Consequently, I mix the USB signal with IF+ST, before feeding it to the filter. The LP output is then mixed with the ST frequency to the speaker/earphone. (Note that zero beat is not useful in the analog implementation due to noise and bias.) Best regards Anders, SM5KAE PS I get some tiny spikes 1 kHz apart in the FFT of the USB data. Are these generated in my setup? DS

Hi My reader is very erratic with a lot of *. can someone who has a good setting let me know how they are please -- Martin DK3UW

I have noted that my RTC is wildly inaccurate, gaining 7 minutes overnight. I have removed it from the display...do not really need it. Does anyone know if the GPS module disciplines the clock or VFO frequency ? de VK6XT

One of my BS170's fried yesterday, and I am replacing all 4 of them. Using the excellent info at /g/QRPLabs/wiki/37486 , I am trying to determine if other components were damaged. I have removed all of the BS170's , and looked at the signal coming out of IC503. The voltage levels are okay, but it's neither a clean sine wave or square wave. Is that okay ? Thanks and 73, Steve, N2IC

Hello, I bought a QDX used and never got around to using it. What is the best way to tell what voltage it requires and if it is high or low band? I believe it is 12v and low band, but not 100% sure. It power on ok with different voltages, and wsjtx allows me to select any band. I didn't want to try txing since I might be using the wrong voltage. Thanks!

Somebody asked me how I access the QMX terminal settings if the radio is connected to a headless Raspberry Pi that I can connect to only with a text based ssh connection (or through a browser window with ttyd). Without a graphical desktop system, tools like Putty don't work. So, here are some notes on using GNU screen for this. GNU screen is a text based terminal multiplexer that is widely available on Linux machines. If it isn't installed on your raspberry pi, you can install it with 'sudo apt install screen'. I often use it so that, after I connect to the pi using ssh, I can create multiple windows (tabs) that I can switch between to run multiple programs. If my ssh network connection to the pi is closed, programs running in screen windows (like ardopcf or pat) continue to run, and I can reconnect to them later. See 'man screen' or various online articles and videos for a description of this normal usage. A less well know use of screen is to connect to a serial device with it. So, if the QMX is connected to the pi with a USB cord, so that it appears as virtual serial port '/dev/ttyACM0', you can open the QMX terminal using the command: 'screen /dev/ttyACM0'. Just like when connecting with Putty, this displays a blank black screen until you press <Enter>, and then you will see the QMX terminal menus. Keyboard input including arrow keys should then work as expected. However, there are two things that are different than when using a program like Putty. First, Ctrl-Q, which Hans chose to use to back out of various sub-menus and screens, does not work when using GNU screen. To send Ctrl-Q to the QMX, you need to type Ctrl-a and then q. Second, to close a screen window, usually after selecting the 'Exit terminal' command in the QMX menus, type Ctrl-a and then k. This will prompt you with 'Really kill this window [y/n]', so type y. If you are already running screen, perhaps with multiple windows, you can also open a new window to connect to the QMX by typing Ctrl-a and then typing ':screen /dev/ttyACM0' (without the quotes) and pressing <Enter>. Once you type the colon (:), it and the remainder of this command will appear in the lower left corner of the window until you press<Enter>. When you are done, typing Ctrl-a and then k will close this window but not any other screen windows that you have created. Hopefully some of you will find these notes useful. Using the QMX terminal is even more important now with the changes in the new SSB beta firmware. Peter LaRue AI7YN

Forgive me if this has been already asked, but I cannot seem to find the answer. My QMX+ is showing some signal every 500Hz in USB mode (and in DIGI mode) on RX. I hear it in the headphones as a light tone or series of tones a little louder than the static. My Yaesu FT-710 doesn't hear these tones when connected to the same antenna. This morning I made another MFSK144 contact with the QMX+ with a station I had just contacted on the FT-710. Same set up, same antenna, only difference is the radio used. The FT-710 was "hearing" the MSK144 signals, but they were light. The QMX could not "hear" the same signals, the "birdies" were louder than the signal. Almost as if AGC was adjusting to the birdies and not to the background noise. Here is a screenshot of the waterfall in WSJT-X showing the birdie signals. Notice the fairly solid lines every 500 Hz and the not quite as solid ones every 250 Hz. I see the "birdies" on every band, but they get more pronounced the higher the frequency is. At 40m they are barely there, at 6m very obvious. Does anyone know what they are or how to get rid of them?

After the great BS170 meltdown on my QMX, I'm down to replacing Q507 (Q503 and the BS170's have been replaced and look good). I do not have a hot air rework station - only ChipQuik. It looks like the drain is a pad, not directly accessible with a soldering iron. Suggestions on how to replace Q507 with the materials I have ? 73, Steve, N2IC

Just finished QMX build and I can’t get my Mac to recognize the USB so as to upload firmware. I am powering with a 7v power supply. I am using USB c to usbA and then an adapter. Have tried two other cables with no success. I have seen all the tips on YouTube and also page 63 in the manual. Feel like I’ve wasted $150 on this radio and likely never to get it to work. I will try on a Windows machine if I can borrow one this week. Other than that don’t know what to do. Bill, KJ5IVB

One for Hans … Used the latest V6 SMD version yesterday Less to do and makes wiggling the synth in and out of a U3S stack much easier Curiosity. A super- tiny link wire, hand -added between the 2 FETs (3.3V?) seems to duplicate existing tracks. Was the Via omitted?

Hi QMXies. As a sota enthusiast i was missing a working clock (on the QMX .. not QMX+) regardless if batteries have been removed before. There is everything there also in QMX, but the 32kHz Q and the buffer battery. I (carefully) released pins 6, 8, 9 of the STM32 from the PCB, soldered 3 thin wires to the elevated pins ant fixed them with epoxy glue. Then attached a 32kHz Q to 8 & 9 pin wires. As i don't need the PTT output for sota, i removed the PTT connector, which made room for the CR2016, attached to pin 6 wire. Settings "real time clock" set to QMX+ RTC and "set time" -- voi la. Now the RTC keeps on running while QMX is in his transport box without any power attached :-) I have to confess, you need some skills in working with very small soldering tips under the microscope, as the pins of the STM32 are really close together. Solder bridges don't have to bring you out of concept ;-) :-) Wolfgang OE3WHU