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Hi Willie Yes, spot on. That, and whether the diode and/or zeners add anything to the receive noise floor. Probably not. But I need to measure, simulation isn't good enough for me :-D I tried to

Karl, I would call these good.? There are only 2 windings on L12.? Both are used on 80, 60, 40, and 30 meters.? The first winding is used for only 20 meters.? The capacitor selection makes the

Willie, Simulation FFT says that the commutating diode does no damage to spectral purity. This makes sense for two reasons: 1) The current flowing through the diode is small and capacitive

Maybe I could shift some of those BPF and LPF numbers around to get closer to the peaks.... What you think? I could not have even done this without the stuff Rick sent! 73 Karl KI4ZUQ

It works! It receives! I removed the 22pf C403 and here are the results:

Rick, I think he actually means it's too bright. I have changed the limiting resistor on every QCX-mini and now QMX that I've built. Just too bright, especially at night. No, I don't have the pin 3

Dan, take a look at this thread. You may be having the same problem. /g/QRPLabs/message/107812

Check for contact between pin 3 on the LCD module, and the inductor housing, on the power supply board above it. This will cause the backlight to wash out the display, like you are describing.

And, of course, the third question is if adding the commutating diode and/or the zemers will affect the output characteristics (spectral purity, spurs, harmonics), in such a way as to render

Hans & John, Thanks for the excellent explanation! I'll add the 1N4148 to L14. I can't see that it'll do any harm anyway, and it probably will help. -- 73, Dan? NM3A

Hi all. After slooowly assembling my QMX main board, I finally completed mounting all the electrical components. I don't any issue with the potential buck regulator short issue. I measured all tthe

Yep, that would certainly make sense, and has been mentioned before. However, it would require a fairly major revision to wsjtx, and since it works as is (even if it’s not technically the most

QCX 40 has been sold. -- 73/72, Dean K5DH

Suppose that WSJT-X could be modified to side-step the whole 'translate the desired rf frequency to an audio tone, send the tone out on an audio cable to the radio, where the tone is mixed in on the

Dan, The QMX has a PMOSFET modulator that can gracefully ramp down the supply voltage to the power amplifier stage, under digital/MCU control. That circuitry is essential for the QMX wave shaping