Pre amplifier

Transformer T1

  • BN43-2402
  • Primary: 14 Turns
  • Secondary: 1 + 1 Turns

Transformer T2

To drive a 50 Ohm antenna or 50 Ohm band pass filter:

  • BN43-2402
  • Primary: 12 Turns
  • Secondary: 8 + 8 Turns

To drive a final stage with MOSFETs the Turns are those of the following schematic, i.e.:

  • BN43-2402
  • Primary: 2+2 Turns
  • Secondary: 3 Turns

10 W amplifier

To obtain 10 Watts from 1 to 14 MHz and 5 Watts at 21 and 28 MHz I added 2 x RD16HHF1 in push pull. 

For the best results they need:
  • some gate polarization (especially at 21 and 28 MHz) to work in class AB to be set by two potentiometers
  • a command to set such polarization only when transmitting to avoid useless heating and power consumption

Low pass filters.

In both cases the output is more or less a square wave and it needs to be filtered before going on air.
To build some low pass filters I found this practical document. 
https://www.qrp-labs.com/images/lpfkit/gqrplpf.pdf