The Alexanderson alternator is driven by a 600 horse power asynchronous two phase 2300V electric motor, driving the high frequency generator via a gear box. The transmitting frequency is in direct proportion to the speed of the motor. One of the great challenges with the SAQ transmitter is to maintain the motor speed at a constant rate, both when the transmitter is idling (Morse key is up) and when it is transmitting (Morse key is pressed down). This is done by an automated control system, however at start-up it needs ”tuning assistance” to find the right frequency. After the initial tuning of the transmitter, we normally can keep the frequency between 17190 and 17210 Hz. On the electric motor, with a speed of 711,3 revolutions per minute, this represents a maximum deviation of a single revolution per minute between idle running and full load.
Fredrik / AlexanderSAQ
(thanks to Ola Hernvall for technical assistance)