PA
Because I need about 8 Watt in my shack to drive the coax to the POTY, and keep about 3 Watt left on the POTY, I have chosen for the PA from DXPatrol. It can do 12W, but I only put 18V on it. The output generates about 3.3V on the PWR output pin of the PA.
At 18V it draws about 2 Amperes.
Make sure your 13.5V power supply can do this easily. In total it is about 3 Amperes.
An old PS which is designed to do 4 Ams, was not doing a good job. So I had to use an old fashioned PS, which was doing ok.