QSK or not QSK ??

Well, the QRX is a full QSK kit, so it would be a waste to build an amplifier without these features. So, I decided to build a QSK block 'around' the amplifier, as you can see in the overview of the scheme. The design comes from QRPLab, TNX guys !. Let's see whether it works fine for me. The explanation of the circuit can be best read on the site of QRPLabs ( https://qrp-labs.com ). Look for the 50W kit. QRPLabs uses IRF510 FETs. I use IRF530 FETs, and therefore a different design for the amplifier. But in the basics it should work also.

 

A few comments from my side:

  • The design is based on implementing electronic switches between input and attenuator, filter output and RF-out, and RF-input and RF-output. So three switches.
  • With Q4 and Q6 you make the bias voltages for the diodes at the begin and end of the Amp, pretty straight forward. Switching the input and the output is a little more complex. The bias voltages over the diodes should be higher then the RF voltages, otherwise the diodes don't stay shut. It is done by the voltage doubler with the diode sets (two because of the high voltage of 140V at 50W !)