The QRP-Labs 50W amplifier makes a great (and inexpensive) single-band amp for the HT-1A.
To key the amp, a 5v keying line is needed from the HT-1. ?On the HT-1 display board I tapped into the line supplying voltage to the red transmit LED and used that to feed a small reed relay mounted inside the rig's case (with a diode across it), connected to a 1/8" phone jack on the back.
I'll attach the interface circuit I used to provide 5v to key the amp.
73 Howard K4LXY
