Many thanks for your feedback on the today’s SAQ test transmission!
Today was very special, as the transmitter has not been in operation for a few months, due to extended building maintenance.
Additionally, during this period, we have made major service on the compensation liquid rheostat, cleaning it out and filling with new fresh water.
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 the start liquid rheostat, 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 compensation liquid rheostat is connected in parallel with the first, resulting in a lower resistance, giving the drive motor a good “torque boost” in order not to drop in speed when all the power shall go out to the antenna.
As the compensation rheostat only is connected when the morse key is pressed down and as the actual load only can be determined when the alternator is connected to the antenna, we have been unable to refill the compensation rheostat with sodium carbonate until today. We use food grade sodium carbonate, with very low chloride levels.
After some calculations, we filled 250g into the rheostat and started the alternator. We managed to get a good tuning of the drive motor speed but the compensation rheostat was at its upper max position, indicating that the sodium carbonate concentration was too low.
So, we added another 50g, retuned the drive motor, added yet another 50g and made a final tuning of the drive motor.
That was what you were hearing during those long tuning sessions today.
After that we ran our “VVV VVV VVV de SAQ” message a couple of times to check that we got good speed stability and good power to the antenna.
So, things look good for tomorrow’s transmission which we very much look forward to.
Fredrik / Alexander association
