Hem SAQ Forum SAQ Transmissions SAQ Transmission Exact Frequency

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  • #3687 Reply
    John Stuart

    To what accuracy can we expect the 17.200 kHz frequency to be?

    One difficulty we have in North America is the electrical noise from the 287th harmonic of 60Hz = 17,.220 kHz
    Of course in Europe, the 344th harmonic of 50 Hz = 17.200 kHz
    Given the accuracy of modern receivers, and the proliferation of power line harmonic generators, it would be nice to avoid those two transmission frequencies.

    John Stuart, KM6QX
    Lafayette, CA

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    • #3691 Reply

      Dear John,
      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)

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