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QCX alignment : what is it, and when do you need to repeat the process ?

 

Could someone please have a go to try and explain in simple terms what the alignment process on the QCX actually does ?
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I understand the manual says to do this once construction is complete. But are there other situations where you would need to repeat it ? Possibly after tweaking L1/2/3 for optimum power output ?
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Thanks in advance
 

On 13/08/2024 09:55, Eben Fourie via groups.io wrote:
I understand the manual says to do this once construction is complete. But are there other situations where you would need to repeat it ? Possibly after tweaking L1/2/3 for optimum power output ?
The manual says:-

Band-pass trimmer capacitor peaking, C1
? I-Q amplitude balance, R27
? Audio phase shift adjustments, R17 and R24

The first is obvious, unlikely to change appreciably with different antennas or LPF adjustment.

The other two affect the reduction of the unwanted sideband level. Not likely to change.

73 Alan G4ZFQ
 

As Alan says.
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If the QCX has recently been built by you:
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1. Make sure C1 is not at either maximum or minimum at the signal peak...if it is then you will need to make alterations to the input BPF ...either capacitance or inductance.
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2. Adjustment of the three variable resistors interact with each other slightly, repeat several times to make sure you have the best results.
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If you have a fault don't automatically assume it needs re alignment...check it through logically...altering the above may make it harder to find the fault.
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73 Steve G4EDG?

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