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Showing posts from March 29, 2017

U3S 5W PA continued

My   U3S project  is  almost finished it took a lot of solder smoke. The plan is a WSPR radio beacon operating  as PU7ZWT from HI11ln at the allowed bands 160m 80m 15m 12m 10m and 6m with about 5W power at 12 10 and 6 The 5W PA could not reach 5W level  at the higher bands. With the PA  inside the case using the bottom of case as heatsink is effective 20W DC input it stays cool. But i had some self oscillation issues and unwanted reboot at TX start. No short thin coax but a twisted wire connection between U3S and the LPF unit resulted in more output. A single BS170 reached 700mW at 5V 28MHz and 600mW at 50MHz With this drive level it should be easy to reach   5W with the PA if the power gain was 10dB but is is not. Important is reading excellent manual and application notes before starting  contructing That I did not good enough.   My notes: 1   10R to the gate of the RD15HVF1 this mod must be done. 2   The "Key"  signal  is used to switch the PA 12V


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