Just in case anyone else gets the same symptoms:-
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I built a v2 PCB QMX+ and all went well until i went to transmit into a dummy load and the swr protection activated and a high swr was indicated via the terminal program. I checked the load with an swr meter and a VNA and it looked fine. I was somehat surprised that when the dummy load was DISconnected the swr dropped as did the swr alarm!
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I suspected an error winding T507 so i spent the next 2 nights rewinding it changing the 4 permutations of winding directions but nothing changed. The DC voltages out of the detector diodes matched what the terninal program was saying.
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On the 3rd night I tried checking resistances, which is hard to do as the windings are DC grounded. I removed T507 yet again and checked the resitances. Measuring across R522 showed 50 ohms. Measuring across the tracks to R520 did not reveal 49.9 ohms! I then measured across the solder pads physically on R520; still not 50ohms. Examination under a USB microscope (i knew it would come in useful one day!) showed a break in the resistive element. I found a 51 ohm resitor as a temporary measure , replaced T507 and all worked perfectly. I subsequently got a 49.9 ohm resitor and put it in.
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Now you can buy blank QMX+ cases from the ship I have now built an ATU100 into one of them (I have one that would work inside the QMX+ box but that would mean hacking the QMX+ front panel, i will wait till the QMX+ software supports it.) The other case has a 3 x 18650 battery pack () ?which powers the radio well through a dropper diode
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Dave
G4FRE
