W8DIZ “Diz,” from Kits and Parts SK, R.I.P had a really cool way to do this-
Use a 78L05 regulator tied to the amp B+ in (~22V in the QRP Labs case)
Tie the output of the regulator to amplifier PTT (5V active high)
Connect the gnd pin of the regulator to the PTT circuit of the rig.?
So when the PTT provides a ground to the regulator, it switches on, and 5V is used to activate the 50W amp.
I used this idea to build a 50W amp and one of Diz’s 5Watter rigs together in a case. At 12V in, it makes about 25W, and runs cool.
Larry
KB3CUF?
