I recently completed a QMX+ kit.? The firmware loaded, switch on current 90mA.? I used the puTTy terminal programme to look at all the parameters/values that the QMX+ should exhibit.
I found that power output was as follows:
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160m???????????????????? 5.85W (calculated – oscilloscope across dummy load)
80m?????????????????????? 4.66W
60m?????????????????????? 1.9W
40m?????????????????????? .75W
30m?????????????????????? .36W
20m?????????????????????? 0.2W
17m?????????????????????? .07W
15m?????????????????????? .2W
12m?????????????????????? .04W
11m?????????????????????? .03W
10m?????????????????????? .04W
12m?????????????????????? 0W
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I first suspected that the filter toroids or the transformers may have been incorrectly wound but subsequent checking (firmware sweeps, rewinding T501 and T507, attaching a Nanovna to each RF & LPF ?showed they were fine).
My concern rose when I looked at some voltages.? The CLK voltages were all ok but on measuring the outputs of IC’s 501, 502 and 503 from CLK2 input gave some interesting results.? These were p-p voltages with a 100MHz oscilloscope.
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IC501 (74AHC1G86D)
??????????????????????????????? 1.8MHz???????????????? 14MHz????????????????? 28MHz? ??????????????? 50MHz
Clk2 input??????????? 4.7????????????????????????? 4.8????????????????????????? 4.9????????????????????????? 5.0????????? (Pin1)
Pin4 output??????? 4.2????????????????????????? 3.5????????????????????????? 2.8????????????????????????? 2.7
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IC502 (74AHC1G86D)
Clk2 input??????????? 4.7????????????????????????? 4.8????????????????????????? 4.9????????????????????????? 5????????????? (Pin1)
Pin4 output??????? 4.2????????????????????????? 3.5????????????????????????? 2.8????????????????????????? 2.8
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IC503 (74ACT08D)
Pins2,5,10,13????? 3.3????????????????????????? 3.3????????????????????????? 3.3????????????????????????? 3.3????????? (From TX 3.3V)
Pins 8,11????????????? 7.4????????????????????????? 4????????????????????????????? 1.6????????????????????????? .4??????????? (gates of Q503/Q505)
Pins3,6????????????????? 7.4????????????????????????? 4????????????????????????????? 1.7????????????????????????? .6??????????? (gates of Q504/Q506)
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Q503/Q505
Drain???????????????????? 63V??????????????????????? 20V??????????????????????? 4V?????????????????????????? 0
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Q504/Q506????????
Drain???????????????????? 65V??????????????????????? 19V??????????????????????? 6V?????????????????????????? 0
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There are no passive components in this part of the circuit so my conclusion is that IC’s 501, 502 and/or 503 do not have the High Frequency response they should.
Are the IC’s faulty or is there something else I should check.? Some expert help here is needed.
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Greg, ZL4GW
