Circuit Diagram, 1929
circuit diagram of the KGO transmitter facility was submitted to the
Federal Radio Commission as part of the station's license renewal
application in October, 1929. It describes the construction of
the custom-built General Electric transmitter, serial number "KGO-1".
There were undoubledly several transmitters and numerous
modifications made between KGO's original 1924 air date and the
creation of this drawing.
Here is a detail description of the equipment for our "technically-minded" readers:
the studio control room: The circuit reads from right to left.
Three levels of amplification with volume control were used to
amplify the program audio signal to 17.5 watts, at which point the
program was sent by wire line a short distance to the transmitter.
There is an RF trap at the output transformer to keep the
transmitted signal from interfering with the program.
the transmitter "power house": The carrier signal (790 kHz) is
generated by the crystal oscillator at far left. There is a
choice of three crystals, which were housed in a temperature-stable
thermostat-controlled enclosure. This is followed by four stages
of RF amplification, produce a 1 kW drive signal. The final
RF amplifier is a single water-cooled UV-207, rated at 20 kW, which
operated as a Class "A" power amplifier to produce a carrier power of
7,500 watts. The audio signal from the studio
building, which enters at the right, passes through one buffer stage to
a pair of UV-207 modulator tubes. Heising ("constant current")
modulation is used. The antenna is inductively coupled, and fed at both ends in a unique "multiple-tuned" configuration.