Hem SAQ Forum SAQ Technical Discussions What is the expected frequency accuracy of the transmitter?

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  • #10518 Svara

    My receive antenna is high-Q, thus about 80 Hz wide at the -3dB bandwidth points. It will be tuned for 17200 Hz. How close to 17.200 kHz does the alternator normally run? Thank you. Ed, KI6R, Arizona.

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    • #10519 Svara

      Dear Ed,
      Thanks for your question.
      The Alexanderson alternator has a built-in automatic speed control system. From the high frequency generator, 64 individual tangles, each of them picking up the magnetic flux from the rotating disc, are each supplying 100V 30A to the magnetic amplifier, connected to the antenna. However, one of them is used as a feedback to a built-in resonance circuit, located behind the control panel. This circuit can control the feed current to a set of transductors, which each can adjust the supply voltage to the main drive motor. The speed of the drive motor is in direct relation to the generated magnetic flux, i.e. the transmission frequency. So the feedback signal from the Alexanderson alternator will allow for a very stable frequency, usually within +/- 10Hz.

      Fredrik / Alexander association

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