The Heathkit Transmitter Model DX-40 was designed to permit maximum versatility at a reasonable price. It features up to 75 watts input with three switch-selected crystal positions for the novice operator. It includes controlled carrier phone operation and provision for VFO excitation for the general class ham. It has sufficient output to drive larger transmitters when the station is expanded, yet is small enough for field day operation.
The DX-40 consists of one power supply, three radio frequency stages, and two dual-triode audio stages. Pi network output coupling is used to facilitate antenna matching. The panel controls consists of a key jack, operation switch, band switch, drive control, pilot light, final tuning, meter switch and antenna tuning. The mike connector, crystal switch, output connector, VFO input and auxiliary power socket are located on the rear chassis apron.
The following block diagram and circuit description will give the builder abetter understanding of the transmitter. This knowledge is an invaluable aid to construction and as such is well worth reading thoroughly. LETHAL VOLTAGES ARE PRESENT AT MANY POINTS ABOVE AND BELOW THE CHASSIS. CONSEQUENTLY, GREAT CARE MUST BE EXERCISED WHEN ANY TEST OR ADJUSTMENTS ARE MADE.