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Showing posts from November 21, 2012

QTX 475 kHz

output V over 50Ohm  ~72W Rf   at input  76W (25Vx 3A)   N=96% ! ? V drain puls had to modify the total capacity  of C2+C3 to 10+6.8+6.8 nF and the output C4 6n8 + 6n8  to archive maximum output. But at 25V still could not produce 100W out I did change R4 to 1k  because of latching problems I had earlier that cost me a few IRF's  Drive level increase  does not change the output in this class D  type switching mode. The Flex1500 XVTR/C port  0dBm at level 30% is sufficient. Also the K3 XVTR out level was perfect to drive the QTX.  Class D is perfect for CW WSPR modes. The Drain pulse form seems correct. Optimising L3 for maximum output did not bring  more output. Po drops as soon as a ferrite bar is approaching L3. I would expect that L3 could be increased when dropping the frequency from 500 to 475 kHz After re-arranging  C2 C3 C4 The output increased to 75V/50Ohm 112.5W 50Ohm dummy Bird 8251 C2+C3  is now 10n+ 6n8+ 4n7 The C


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