This transmitter was finished on or about 8/6/02. It was built using the December 1929 QST article called "A Single Control Transmitter by George Grammar. A few modern parts were used where performance was needed, but as many old time parts were used as possible. I built this transmitter to be used on a regular basis, so I strived for as clean a signal as possible with this simple a circuit.
A little thoery on its operation:
The white coil in the lower right is the grid tuned circuit. The coil resonates broadly in the 80 meter band against the capacitance of the tube elements and the distributed capacitance of the coil windings themselves. The grid coil is coupled to the tube via a 250pf "Solar" molded mica condenser that was manufactured in the late 20's. A modern 10K carbon grid leak resistor is used in parallel with the Solar mica condenser.
The tube pictured is a #10Y. A #201 at reduced plate voltage will also work as well as (possibly) a #45 triode. The plate circuit consists of a modern RF choke to the 250V B+ supply. The plate is capacitively coupled to the tank circuit via a .01uF mica transmitting condenser. The tank consists of 12 or 13 turns of 1/4 inch copper tubing in parallel with a 23 plate Cardwell tuning condenser. The cold end of the coil faces the front of the rig. The link is a single turn of #12 wire slightly larger in diameter than the tank coil. The coil is supported on 2 beehive insulators scarfed from an old 1KW broadcast transmitter. They appear identical to the insulators used in the '20s except those were a dark brown color. The shape is the same.
The transmitter tunes the 80 meter band. In playing with this rig, I found it can be modulated by putting a carbon mic element across the link and tapping the tank up a turn and connecting the antenna there. Dont operate it AM tho, as it FM's as well as it modulates AM.
The transmitter is built on a stained pine board 8X13 inches.