Final Amp/Filter Schematic

Values for the output filter are for 20 Meters. Other values can be obtained from the original circuit found in most of the late 80's and early 90's ARRL Handbooks.

MRF472s will also work where the MRF476s are located. Be aware that the pin connections are different for the MRF472s.

I did not use the optional resistive pad in my prototype. It does not need to be included unless a much lower output is desired.

At L3, I have used a low value wire-wound RF choke and the circuit worked well. Any bead close to what is indicated will work, I have also used a type -43 bead and got it to work. Don't be afraid to use what you have as I have not found it to be critical.

If you do substitute for L3 and don't get the output you expect, suspect that is the problem and experiment. I have found the circuit to be very easy to build and works every time.

Use a 50 ohm, 5 watt resistor (or larger) as a load for the output circuit while experimenting.