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The wiki page QMX QMX_plus Debugging has been updated by @Ludwig_DH8WN <DH8WN@...>. Compare Revisions

Hello! I've noticed that SWR protection stops TX when I try to use QMX with one of my PA. When I measure SWR with connected PA threw QMX hardware test it shows 1.8-1.9. And it causes SWR protection actuation (even if SWR protection level is 3 or 4 by the way...). When I do SWR measurement with Nano VNA or another transceiver they measure SWR = 1.1. So it looks like QMX is incorrect. That is strange... When I do not use PA then QMX SWR measurement tool provides correct figures (compared with Nano VNA). Any ideas? BR/Sergey UB3AZK

GM QDX’ers. I was gifted a QDX still in kit form so I spent a day building it this week. Except for one band, 80M, I got between 4.8 and 5.4W output which is optimal. The cure for that was to just put some more heat and re-solder leads on the inductors. I get reports of anywhere from -2 to -20. My issue seems to be with the received signal getting into WSJT-x. Although I’ve made a dozen or so contacts on 20M and 30M, the db meter (I’ll call the S meter) barely hits 15db maybe 20db on a real strong signal. Never higher. Most signals reports I give out are in the -17 to -10 range which would correlate with the db meter. I know from experience it should be a lot higher than that. I’ve seen no signals decoded on 40M or 80M but I haven’t listened at night which is going to be the most likely time to see those out in the NW. I’m using a retired MacAir as the computer using OSX. All radio and audio settings are set to the QDX settings and to full audio by default. The Radio is set to a Kenwood TS-440. It gives the impression there is not enough signal/audio getting into WSJT-x but I’ve got no way to adjust that. The antenna is a hexbeam for 20M and a 100ft high loop for 30/40/60/80 The version of QDX is 1.4 Any insight into this receiver issue would be greatly appreciated. I can live with the way it is now but I think with the receive signal stronger, it will show me a lot more stations. It may be MAC thing. I just don’t know. Thanks. John / K7RLD

With the official SSB firmware now supporting 3 virtual com ports, are we able to use the soundcard and I/Q at the same time? So can I do digital modes and have a panadapter? Would I be able to use IQ for a panadapter and still be able to use my mic for SSB? Thanks Randal VE7NHW

I have two QMX rigs, one I built (mid band version) the other I ordered assembled. The one I built was successful with the SSB calibration. However, the one that I received assembled from QRP Labs (high band version) fails the initial phase calibration on 20 meters, but passes on 17, 15, 12, 11 and 10. After which the all the bands calibrates fine with USB and LSB. I'm not a big SSB phone guy, but out of completion I would like to know if I should send back the High band QMX. I did the configurations via a USB cable and Putty in Linux. I haven't tried to initiate the calibration via the radio tools without being connected to a computer. Any suggestions?

I needed to replace one of the 1n4007 diodes in my QMX (I cut the lead for an experiment) so I went looking for a replacement. None of the 1n4007 diodes at Mouser have the small diameter leads like the ones from QRP Labs. They are all about .7mm diameter where the QRPLabs diodes are more like .3mm. I ended up ordering Vishay diodes with the fat leads. I had cleared the holes with the solder sucker but the leads still did not fit so I used some PCB drill bits to clear the holes and finally got the diode in there. Hopefully the via barrel is still intact. I am waiting for some caps to put it back together and try it. Any discussion about these diodes? My experience is that 1N400x diodes all had fat leads. Thanks, Tony AD0VC

Hey everyone, short story: After one of the PA transistors died, I replaced all of them. Now I only get 3,5W power on 80m but less than 0,5W on the other bands. Is this because of insufficient (fake) replacement transistors or could something else be damaged? long version: I built the QDX and after some wire pushing on the coils I got 5W@9V at all bands and was super happy. I am measuring DC on the detector diode of a QRP dummy load. After a some FT8 operation using an antenna, the output power dropped to 2.5W on all bands. Then I accidently shorted one of the transistors during some measurements and the output power went to a few mW. I removed the BS170s from the circuit and measured them using a diode tester and one was definitely broken. Then I bought replacments for the BS170 transistors at three different online shops (not really trustworthy ones). However during testing after replacing the transistors, the QDX behaved identically with each of the different BS170 sets. There was about 3,5W output power at 80m but only less than 0,5 W on the other bands. I supect that the transistors are fake because their performance decreased with higher frequency. But I am not sure. Is there a way to validate this? I used a LCR-T4 transistor tester to measure the transistors. This showed differences in capicatance. The original BS170s from the kit have 50pf, one of the sets I bought has 60pf and the others 30pf. Does this give any indication if the parts are correct? Or could it be possible that someting else in the QDX is broken? Maybe the IC that drives the PA (74ACT08)? However, I measured 2.5V at the BS170 gates so I guess it still works. Unfortunately I do not have an oscilloscope at the moment. Or is maybe the PIN diode switching circuit for the LPFs not working anymore? Reception is still fine! I would be really grateful for help on finding the issue! regards Chris

I wanted to try using WSPR, but every time I reboot, I have to set the time on the QMX again. A friend told me there's a GPS module that can help calibrate the QMX's time. I thought to myself—my phone already has GPS, so why buy an extra GPS module just to set the time on the QMX? So, I added a feature to calibrate the QMX's time through FT8TW. https://youtu.be/l8dey0vc6_E

Jeff has done it again! Repaired my mid-band QMX - a couple suspected cold solder joints and improperly wound T507 (how’d I do that?). Included was a free wax and polish (Jeff removed caked solder flux and scrubs the board with alcohol). All done in a day or two. I had my QMX back in ten days (could have been faster but that’s our slow postal service). it is so nice to know that Jeff is available to bail you out should your build fails. I’ve built two QMXs and he’s made them right for me. Thank you Jeff! And Hans! (his info is on QRZ) Phil K3UT

This seems to be a complex problem because I do not understand what is happening. I will try to explain as best as I can. QMX mid bands built for 12 volts and Z-11 Pro auto tuner. I start on 40 meters and go to hardware then SWR tune and start the tune. The tuner light move and ends when a <1.5 SWR is reached. I then go to iambic and send CW at about 20 wpm. After about 10 dits the tuner jumps up to over 4 and the S protection letter shows on the screen after the last number. I cycle the menu, go to hardware, SWR tune and it shows <1.5 SWR. I go back to normal CW and the same pattern shows up again. It happens on multiple bands and is frustrating because I can't complete a POTA contact let alone a ragchew. My sBITx is also low power 1 - 4 watts and does not do this action with the tuner. Any ideas where to look? 73, Dean/ N2TNN

Just upgraded from pre-SSB version to 1_02_000 and now the QMX doesn't start again. - Only POP at headphones - No display - No serial port visible at computer - With new upgrade all HW tests worked fine Battery voltage OK (not of course measurable from device). The device worked fine before this upgrade. What should I try to fix this?

When testing my newly built QMX+ I was getting high SWR readings while running the diagnostics SWR test. Even when connected to a dummy load the readings were around 2.7 to 1 across all bands. I removed and re-wound T507 (twice) but could not resolve the problem. So I removed T507 for a third time and started to check component values around the bridge circuit. I found that R520, although marked as 68X (49.9 R) , actually measured as 124.5 K. Has anyone else seen this problem. Regards Stephen

I still use TS 480 for the setup of N1MM. When I am in Run and press the up or down key the QMX + changes to RIT .- .030 but cannot be modified then. I have to exit from that on the QMX+. It would have been perfect, if the QMx+ would follow the RIT in run. any suggestions ? -- Martin DK3UW