Hi, I recently built the QDX (for 10m - 20m) and it went really well. So far, I haven't been able to test with an antenna because of the weather, but I have used the internal test tools.
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Doing an RF sweep, I noticed that most bands are good (or acceptable for some), but the 20m doesn't seem right.
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Here are measurements for 10m and 20m:
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RF Filter Sweep at 10m
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RF Filter sweep at 20m
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As you can see, sweep doesn't look great for 20m.
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My first question is, am I measuring this correctly? I didn't want there to be any spurious transmission signal, so I hooked up a 50? dummy load. Is that necessary or shouldn't I do that? (If this is mentioned in the manual, I must have overlooked it.)
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Secondly, given the response in the second image, what could be wrong? Perhaps something wrong with the toroid (number of windings), capacitors? I'm just trying to determine how I can get to the root cause quickest. I have some measurement equipment, like DVM and oscilloscope.
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Any input would be greatly appreciated!
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73
Sander [VK6PI]
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