Just finished building my QMX Midband. Everything seems to be working fine except that the output on 15m is 3dB below that on the other bands. Here is output power by band and by voltage:
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The scans look more or less OK except for a few outliers:
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Image sweep on 60m is pretty poor:
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on the other bands (e.g., 20m) it looks OK:
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SWR sweep (into a dummy load) looks OK except for 15m:
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I checked my dummy load with my VNA. The SWR is practically 1 (return loss <-30dB) and flat from 0-50MHz. So not sure why the QMX SWR sweep on 15m is so bad.
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ADC I/Q test looks good:
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Haven't been able to test the QMX on the air except for two FT8 QSOs which were working fine.
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This is my second QMX. The first QMX I built was a Highband and while it was working for a while, the sweeps were inconsistent (the ADC I/Q test was horrible) and it suddenly stopped working. My second attempt of building a QMX (this Midband version) seems to have gone better.
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Any thoughts on the low output power at 15m and the poor image sweep and SWR sweep on 60m and 15m, respectively?
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73,
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Andreas, K6AKW
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