This transmitter features solid state grid block keying and a regulated, variable screen supply to adjust output power of the PA.
The plate tuned circuit for the osc and driver are wound on 1/4" dia slug tuned coil forms. The PA tank and plate choke was salvaged from a beat up DX-40 or 60, many years ago. The power transformer is some what unique, having two 60 volt, CT windings. These are wired in series to produce 120 volts, then a voltage doubling rectifier produces about 350 volts from that.
It might be possable to modify the HV regulator which adjusts power output by changing the screen voltage on the PA, so that is could be modulated with audio, providing screen grid modulation.
The grid block keying is optically isolated, so the key only sees low voltage. Delayed T/R switching is incorperated, using a 4011 logic gate. A little bit of the new combined with the old.