Valve Transmitter circuit 70W
Posted on May 3, 2017 5805
The variable capacitors C1 and C2 will have their sheets thin Also their insulations will be made of porcelain. The capacitor C3 works at 2kV. All RFCs have an inductance of 2.5mH and can pass a current of 100mA. Transformer T1 has a 8K impedance primary. Insulations must be made for a voltage of 1kV.
Transformer T2 works with primary 220V, as secondary has three windings: A winding for 6,3V, one for 5V (supplying 5R4) and one for high voltage 2X750V, 100mA. 750V filter capacitors have a capacity of 100μF and operate at 450V. They are connected in series and operate at a voltage of 1200V.
At the ends of each elementary capacitor a resistance 100k is connected to stabilize the voltage of the capacitor. Supply of the isolator, oscillator, and modulator preamplifiers is provided by the mains voltage through a silicon rectifier (D) operating at 250V and a current of 200mA.
All resistors other than those listed in the drawing are 1W power. All capacitors except those listed in the drawing operate at a voltage of 300-400V. Once the antenna is in place and is connected to the transmitter, for maximum signal output and range, set the instrument to indicate the minimum indication.