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I have assembled and have working a QMX+, with one caveat; all of the LPF sweeps are bad. The audio filter sweeps, RF filter sweeps, image sweeps, and SWR sweeps look reasonable, although on a couple of bands the SWR sweeps aren't flat across the entire bandwidth swept, but were always good in the ham band frequencies. The I/Q sweeps all looked good except for 160 Meters where the phases were in sync for some reason. Not really a problem for me, I don't own that much wire. Here's the real problem. All of the LPF sweeps are bad. For example: 0 | * .* * * * .* * * . * * .* * * . * * * . | * * * .* * * * .* * * * * * * * .* * * * * * * *. | * * ** * .* * * * .* ** ** ** ** ** ** * * .* * * * ** * * * ** | ** ** ** **.* * * * ** ** ** ** ** ** ** ** * .* * ** ** ** * * * * * | ** ** ** **.** * ** ** ** ** ** ** ** ** ** ** **.* ** ** ** ** ** * ** * * | ** ** ** **.***|*** ** ** ** ** ** ** ** ** ** *** *** ** ** ** **** ** * * | ** ** ** *** **|** *** ** ** ** ** ** ** ** *** ** *** ** ** ** *** *** * * | ** ** *** ** **|** ** ** ** ** *** ** ** *** ** ** ** ** *** *** ** ** ** * | * *** *** ** **|** ** ** ** ** ** **.*** *** ** ** ** ** *** *** ** ** ** * | * * * * * **|** ** ** * * * * .* * * * ** ** ** * *. * * ** ** * | * * * * * *|* * *. * * * * .* * * * * * * * *. * * * * * | * * * * * |* * *. * * * * .* * * * * * * * *. * * * * * |* * * * * | * *. * * * * .* * * * . * * *. * * * * |* * * * . | *. * * * * .* * * * . * * *. * * * |* * * * . | *. * * * * .* * * . * * *. * * * |* * * * . | . * * * .* * * . * *. * * |* * * . | . * .* * . *. * |* * . | . . * . *. * |* . | . . . . . |* . | . . . . . -8 |* . | . . . . . ---------------------------------------------------------------------------- 6 9 12 15 18 21 0 |. *. * * . . . . . . |.* *. * * * . * * . * *. * *. * * * .* |.* * ** * * * . * * * .* * *. * * *. * * * * * .* |.* * * ** * * * . * * * .* * *. * * *. * * * * * * .* |** ** ** ** **** ** ** ** * * ** * *. * * *. * * * * * * **.* |** ** ** ** **** ** ** ** * * ** ** ** *.** ** ** ** * ** ** ** * ** **.* |** ** ** ***|*** ** ** ** **** ** ** ** *.** ** ** ** * ** ** ** * ** **.* |** ** ** ***|** *** ** ** **** ** ** *** *** ** ** **** ** ** **** ** **.** |* *** *** .*|** *** ** *** *** ** ** *** *** ** ** *** *** ** *** *** *** * |. *** *** .*|** ** *** *** ** *** *** ** ** *** *** ** *** ***.** *** *** * |. ** ** * .*| * *** *** ** ** **** ** ** *** *** ** ** ****.** *** *** ** |. * * * .*| * * ** * ** ** ** * * * ** ** * .* * * *.** ** * * * |. * * * .*| * * .* * ** *. * * * * * * * .* * * *. * * * * * |. * * * . | * * .* * *. * * * * * * * .* * * *. * * * * * |. * * * . | * * .* * *. * * * * * * . * * *. * * * * |. * * * . | * .* * *. * * . * * * . * * *. * * * |. * * * . | * .* * *. * * . * * * . * *. * * . |. * * . | * .* *. * * . * * * . * *. * . |. * . | * .* . * * . * * . * *. * . |. . | .* . * . * . * . * . -7 |. . | .* . . * . . * . ---------------------------------------------------------------------------- 16 24 32 40 48 56 64 72 All of the other bands exhibit a similar pattern. I tried looking for something common to all of the filters, but nothing I came up with made any sense given that the other sweeps were 'normal'. Since everything looked OK except for the LPF sweeps, I decided to perform a smoke test. I hooked it up to EFHW at 20 feet and worked Oklahoma on 40 Meters FT8, so the transceiver is working. I don't have the necessary test equipment to check the spectral purity of the output signal so I'm hesitant to continue using it on the air until I resolve this problem. I tried searching for a solution both here and with Google, read a lot about fixing issues I don't have but nothing that pointed me in the right direction. Thanks all for the great ideas I'm about to receive. Andy WB9YXA

I would like to know if I can apply the following procedure to calibrate the Ref frq without GPS? Using a QCX+ 20M Band I would go to WWV 15MHz and read precisely the frequency for a zero beat. If I read 15.003.00 could I modify menu 8.5 to read 25.005.000 with the TCXO and have a more precise QCX+? 73 - Pierre - FK8IH

My newest QMX+ kit Rev 3 arrived and was assembled exactly one week after ordering! The diagnostics test page showed output power (0W) and SWR (random values). Everything else was OK. All sweep tests showed strange results. Yes, the dummy load was in place. So I decided to power off and check all solder joints again. The QMX was on the table without the enclosure and I did not get a good grip on it. As I pressed the Vol button for power-off the QMX moved on the table and the long button press was interrupted, giving *two* long presses like keying Morse M. The display flashed abnormally showing some text and dimmed. All happened so quickly that I did not see exactly what happened. No smoke, no hot components. Now I can not power-on as the radio does not react to any button press. Nothing happens. If jumpered for forced firmware update, no flash drive appears on the PC. This could be a firmware problem. Is it possible that the second long press of the Vol button started the power-on cycle while still powering off and writing data to the flash memory? Clearly, while performing power-off and saving data into the flash memory, the firmware should ignore the button press for power-on. -- 73 Matti OH6BEX

Hello. I was using my QMX on 40m and 20m FT8 with a known good antenna and computer connection, successful QSOs, and no SWR lock outs or other signs of issue. The QMX screen went to all backlight with no LCD characters displayed for 1-2 sec and then went to a mix of full block LCD and some apparently random characters. Screen has no obvious physical damage. I was not transmitting at the time. I attempted basic battery / power troubleshooting to no avail. With a known good power source, it will not power on. Confirmed it is not limited to a screen issue, there is no RX as tested with audio output. What other troubleshooting is recommended? I’m ok with basic electrical repair, but don’t see myself doing and surface mount repairs. And I’m hoping there’s a possible test to rule out failed components and possibly an easy fix. I have explored the archives and didn’t see a similar problem noted. Thanks for any help.

Well, I bit the bullet and installed the 003 FW. Update of FW went all fine, no issue there. I wired up a electret mic I found in my junk box. Tested the mic on pc and sounded fine. I made an adapter using the electret mic and a foot switch for ptt. The Mic and ppt switch works. But... Testing SSB TX with QMX on dummy load and listening on my ICOM 7300, the audio is badly distorted before calibration and even worse post calibration. So much so that the speech is unintelligible. The audio sounds like the QMX is only picking up the peak signals from my voice. Most of the calibration plots look nothing like the example ones from the release notes. And only a few mildly resemble the examples. Adjusting mic gain to about 70 seems to improve the audio. However, every time I key up, there is now an awful lot of noise before I even start speaking. Once I start speaking the audio is ok'ish with a load of background noise. I tried messing about with other SSB settings with no improvements. I did find a second electret mic that gave me similar results. I have now set it back to factory default and seeking advice. Any suggestions? Mel. M0KMD.

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