I just finished my QMX kit and it is working fine. Hans, thank you very much for this great kit and great documentation.
I am eagerly looking forward to the formware development that will make use of ALL the HW capabilities, that you included into the design!
These were my observations, when building the kit for 12V:
- Read the assembly manual carefully
- Wear protective glasses when cutting off wires with a wire cutter. This is particularly true for the pins of the connectors, that are really hard. They will fly off with high energy and I got a bloody finger, when holding it over the pin while cutting, to avoid? having the cut-off pin fly somewhere...
- The QMX will not forgive any assembly errors: I accidentally soldered a capacitor into the wrong place. Desoldering was impossible without destroying the capacitor. Luckily I still had in my junk box a 390pF C0G 100V SMD 0805 capacitor, that I could use as a replacement. Generally SMD 0805 capacitors fit nicely into the places targeted for the through-hole-capacitors. Just fill the hole with solder and then solder the capacitor.
- Carefully file the PCBs, particularly the controls PCB and display PCB, as during assembly into the enclosure, the controls PCB must move through the display PCB cutout.
- Look for the short between Q103 and Q104 on the buck converter board: My board HAD THE SHORT. I was able to fix it, by heating the drain of Q103 and moving it slightly away from Q104. To avoid tension of the gate and source connections to the PCB, I afterwards heated those up.
- When you put in the BNC connector X502 make sure that the flattened part sits on the PCB without a gap. I had a small gap, which did not allow, to put it into the enclosure. Luckily I had only soldered the centre pin and one of the ground pins, which finally allowed me, to heat the two up jointly and put the connector flush onto the PCB.
- Scrape off the enamel from the toroid wires with a sharp knife.In my kit the 0.6mm wires had a super temperature hardened enamel, that could not be burned off with the soldering iron.
- For the SWR bridge transformer BN43-1502 make sure, that you have ALL wire ends scraped off and the straight wires bent, before you insert it and start to solder. I completed first the 10 turns windings and then soldered the transformer onto the PCB. This will leave you almost NO space to fit in the straight wires and bent them 90 degrees. This took me a LOT of time.
- While soldering in the connectors, that will look through the enclosure, make enclosure assembly checks.
- The pins of the female connectors of the power supply boards were too long and had to be cut off. See #2 when doing that.
- I did the first smoke test on 40m with only the 40m LP filter L512/L508 populated:
- Lab power supply set to 7V and limited to 250mA.
- 0 mA current which went up after I pressed the left encoder.
- Connected to PC running Win 10 and the PC detected a new drive. Firmware copied onto the drive and the QMX restarted,
- Display lit up and showed 7,074,00 --> SUCCESS!
- Current consumption was 140mA
- PC now recognized a new device "QMX transceiver" and set it up.
- Also an additional COM port was created. The COM port number depends on?
- the history of COM ports already established on that PC
- the USB port of the PC, that is used for the connection --> if you connect the same QMX to another port of your PC it will most probably get a different COM port number. You will have to change that in WSJT-X / JTDX
- Connected an earphone to the QMX.
- Connected a TinySA as signal generator with 20+30dB attenatuators to the antena connector of the QMX and created a 7075kHz signal with the TinySA --> heard (too) loud a 1kHz tone in the earphones.
- Started WSJT-X, configured it for "Kenwood TS-480" and the correct COM-Port.?
- Pressed the "Test CAT" button and after several seconds (took longer than for other transceivers) the button went green.
- Changed the "Audio" settings in WSJT-X to "QMX Transceiver"
- Closed the config dialog and pressed "Tune" button in WSJT-X --> 30.8dBm output measured with my TinySA after 20dB+30dB attenuators
- Raised the supply power to 12V (after switching the QMX off)
- Same test, now with 12V resulted in 36.3dBm output power (4.3W, which were also shown by my ATU-100 tuner)
- Connected the QMX to an antenna:
- listened to some SSB stations on 40m after having found the place to switch to LSB
- switched back to USB and ran one FT8 QSO on 40m and one on 60m - GREAT
- After this success I wound and populated the remaining 4 LP filter toroids.
- Tested 30m and 20m with WSJT-X and they worked fine.
- Tested 80m: significant raise in noise in the attached earphone, when I touched the "Tune" encoder (no knob mounted)?
- switched QMX off
- looked at potential touch between encoder housing and other parts
- identified cathode of D513 as potential touch point
- moved it slightly to the left
- switched QMX on again
- no touch sensitivity of the encoder any longer
- "Tune" in WSJT-X resulted in 31.8dBm @ 7V and 36.3dBm @ 12V
I think overall it took me 10-12 hours to assemble the QMX kit and it was the most challenging build so far.
The QMX is IMPRESSIVELY small compared e.g. to my DL2MAN-uSDX's and the uSDX-SOTA by WB2CBA and it has much more potential.
Thanks to Hans for developing this masterpice of electronics, software and mechanics.
Have fun building your kits!
--
73, DB2OO -Joerg
