Hem SAQ Forum SAQ Transmissions Question Antenna-Ammeter-Current at about 13:28 CET

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  • #10026 Reply
    Jens Romeikat

    First signals received in Nothern-Germany during testing at 13:28 CET in Germany
    Is it possible to tell which antenna current
    was indicated by the large ammeter in the control cabinet on the right-hand side?
    Twente showed about -75 dBm at the time, -85dBm Background-noise.
    (recordings: https://www.wumpus-gollum-forum.de/forum/thread.php?board=58&thread=400&page=14#132)


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    • #10067 Reply

      Dear Jens,
      Sorry for late reply.
      The antenna current meter, located in the upper right corner of the control panel is an important tool in the process of tuning SAQ.
      The scale is between 0 – 200A, however it is logarithmic and really hard to read at 50-70A where we are today.
      We always try to get as much amperage out into the antenna as possible. On World Radio Day, Feb 13th 2023 we had about 60A on the meter which is just below our target 65A.
      The reasons to that could be many, weather, humidity, temperature, and of course, our own skills.

      Tuning SAQ is a matter of keeping the main drive motor at a very constant speed, both at key-up and at key-down. The speed of the drive motor will directly determine the transmission frequency. There are two large liquid rheostats, filled with water and sodium carbonate, where the resistance can be adjusted by increasing or lowering the water level using a motor operated gate. The rotor of the main drive motor is wound three phase, and each lead goes to one of the liquid rheostats, to three separate copper bars, from which a set of hollow tubes, with different lengths are mounted, hanging down towards the water level. When operating the gate from the control panel, the water level increases, more tubes will come into contact with the water, and the resistance between the three rotor phases will decrease, giving the motor more torque. At key down, a second liquid rheostat will be connected in parallel with the first one, giving a good “torque boost” to the drive motor.

      Another aspect of tuning SAQ is to adjust the tuning frequency of the antenna, to exactly match the alternator frequency. This is done by operating an adjustable inductor coil at key-down and observing the meter for outgoing power to the antenna. Turn the inductor coil until maximum power has been reached. Don’t forget to keep an eye on the speed of the drive motor, so that tuning is done at the correct frequency.


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