My QMX+ kit build is finally working properly.? I had no problem with the build and loading the firmware but neither the tx nor rx functioned properly.? After some transformer rewinding and getting a new oscilloscope probe for testing, I found that the PA driver IC 74ACT08D was faulty.? It performed ok up to 40m but there was little power at higher frequencies.? I replaced it and the TX performed as it should have.? A little bit of toroid adjustment, including removing a turn or two from a couple of the filters and the output power levels were from 7W to 4.5W from 160m to 6m.
The receiver was noisy from switch on and would only detect a signal from 3uV upwards.? It was the same on all bands.? It was only when the ADC IQ analysis was included in the firmware was I able to see that the waveform was't as it should have been.? I suspected the PCM1804 so replaced it.? It removed ok from the board but when solder wicking the pads, four of them lifted.? It took me a week of fiddling to attach the new PCM1804 with hardwired jumpers for the missing pads.? SUCCESS!
I'm very happy with the transceiver performance and the receiver is now similar to my IC7300.
I believe both IC's that I replaced were faulty from manufacture.
I ordered a replacement QMX+ board (kit) a week ago in case I wasn't able to fix the faulty IC's. (Unnecessary now but I like building equipment.)
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Greg, ZL4GW
